Primate Behavioural Ecology Flashcards
Who wrote ‘Orang-utan, sive Homo sylvestris’
What did it describe
Give a quotation
Edward Tyson 1651 - 1708
characterises the anatomy of the ‘pygmy’ (chimpanzee)
“no man, nor yet a common ape, but a sort of animal between both“ - 1699
Define homologous character
Characteristics of different organisms that are similar because the organisms share a common ancestor that also had that characteristic
What is analogous character
having the same or corresponding roles (function) but do not share a common evolutionary origin - convergent evolution
Give Tinbergen’s 4 questions
Causation (how does X work?)
Ontogeny (How did X develop?)
Function (What is X for?)
Phylogeny (How did X evolve?)
Which of Tinbergen’s 4 questions are proximate and ultimate
Proximate: Causation (how does X work?)
Ontogeny (How did X develop?)
Ultimate:
Function (What is X for?)
Phylogeny (How did X evolve?)
Which of Tinbergen’s 4 questions are historical and current
current:
Causation (how does X work?)
Function (What is X for?)
Historical:
Ontogeny (How did X develop?)
Phylogeny (How did X evolve?)
Give proximate and ultimate reasons for why primates groom
Proximate
Grooming appeases tensions
Grooming maintains social relationships
Ultimate
Being stressed is not good for health and survival
Being lonely is not good for health and survival
Natural selection shaped grooming behaviour to enhance fitness
How many primate species are
a) threatened by extinction
b) Critically Endangered or Endangered
a) 69%
b) 43%
How many species of primate are there?
Why is the count not clear?
between 230-270
due to subdivisions of species (e.g. guenons’ diversity where species identification and differences can be quite challenging).
What species was Galen of Pergamum describing when he said ‘the ape is likest to man’?
Barbary macaques (NOT ACTUALLY AN APE)
How does Japanese primatology differ from Western primatology?
While Western primatology is assumed to be neutral and objective, Japanese primatology gives a particular importance to subjectivity, where, according to them, best data are obtained through personal identification to the subject.
Who did Louis Leakey hire to study wild apes to aid his study of human evolution
Birute Galdikas,
Jane Goodall
Diane Fossey
What are the advantages of studying primates in
a) the wild
b) the lab
a) the advantage of natural settings is that wild populations behaviour is ecologically relevant
b) The advantage of captive populations is that external variables can be controlled
What series of steps are needed for long term field research sites to be successful (5)
1) First, habituation of wild primates (few weeks for small primates, to several years for mountain gorillas or chimpanzees).
2) Once your primates don’t run away anymore, a clear understanding of their behaviour and vocalization requires the set-up of an ethogram (list of behaviours with clear definitions).
3) Once your project is well set-up, clear research questions based on clear hypotheses can be proposed, which determines the sampling (quantitative data collection) – e.g. rates and frequencies of specific behaviour.
4) Collection other types of data (rainfall, patterns of food production, availability and distribution of food).
5) After the data collection: statistical analyses, write papers and publish
What is important about the evolutionary proximity of chimps etc to humans, in the study of human evolution?
What is this approach to human evolution called?
behaviour does not fossilize - studying living primates is very important because documenting, analysing and understanding their diversity, their socio-ecology, and their adaptations allow to infer on the evolution of extinct hominids and to infer on the selective processes that took place throughout human evolution and human ancestry.
the comparative approach
Use the example of sticking out one’s tongue to explain homologous characters shared by LCA
This character is present in orang-utans, gorillas, humans and chimpanzees, but not in more distantly related species like baboons and galagos. We can conclude that this character was shared by the common ancestor among these species
What does the comparative approach to study of human evolution allow
allows to identify correlated factors and characters, from which evolutionary theories can be built. This then allows to infer biological principles and selective processes, such as how behaviour is shaped by the social and environmental conditions
Why do we need to decolonise primatology briefly
most field sites located in tropical areas are actually run by Western people.
Thus, there is a strong need to increase and reinforce non-western perspectives on primatology, as well as researchers from countries where primate are located
it is important to support local populations in areas where primates are studied
How endangered are primates?
what are the causes?
Currently, 69% of the world’s population of primate species are threatened by extinction, and 43% are classified as Critically endangered or endangered
from habitat loss and deforestation, to poaching and bushmeat trade, but also pet trade, and global threat like climate change and global warming, and also human overpopulation and the emergence of new diseases and zoonoses
Name a primate species with a very large group size
Gelada baboons (>200 individuals in a group)
Give an example of behavioural diversity between chimp populations
e nut cracking habits in wild chimpanzees, where some groups prefer to use a stone hammer while others prefer to use a wooden hamme
What class do primates belong to
Mammal
What are the defining features of the mammalian class? (6)
hair/fur
sweat glands - thermoregulation
mammary glands
3 ossicles in the middle ear
specialised teeth
4 heart chambers
Presence of neocortex
What are sweat glands and hair adaptations to?
homeothermy
(constant body temperature that needs to be regulated by other means than cooling down or warning up the blood).
What adaptation does the presence of mammary glands in mammals relate to?
related to long gestation periods and long life expectancy.
Milk production is an adaptation enabling intense maternal or parental care of the offspring, needed due
to this long maturation period
What is the importance of specialised teeth in mammals
What about the mammalian neocortex
adaptation to their diverse diets
Increased learning and behavioural flexibility
Is the increase in brain size linear in the phylogenetic tree
No
What is allometry
non-linear relationship between two factors
What is a general law relating brain and body size?
How will we know if an organism has an adaptation affecting this law
General biological law: brain size increases with body size
Adaptation: below or above the allometric line (smaller or larger than expected, relative to body size)
What principle governs the relationship between diet and body size
Give an example of this in apes
The Jarman-Bell principle
states that the food quality of a herbivore’s intake decreases as the size of the herbivore increases, but the amount of such food increases to counteract the low quality foods. So large animals need a lot of food, and to fulfil their high energetic requirements, they will rely on abundant but poor-quality food.
Large herbivores, like gorillas, need to eat a lot of poor-quality food such as grass and leaves. On the contrary, smaller apes like chimpanzees, who eat mostly ripe fruits need less quantity of these food since they are of better quality, even if they are rare
These requirements thus constrain the habitats occupied by animals
Is the Jarman Bell Priniciple true for all types of diet
No
even if this rule is true for most herbivores and frugivores, it doesn’t exactly apply to omnivores, probably due to the diverse quality of their diet. This also explains, to some extent (as it is not the only explanation) why omnivores, like humans or rats, can occupy diverse ecological niche
What are key features of the hands and feet of primates? (4)
Give other locomotion adaptations (1)
high degree of prehensility
Five digits
Opposable thumb
Divergent and partially opposable big toe
clavicle
Do any primates not have a thumb?
What type of loss is this?
What is the benefit of this loss?
Ateles (spider monkeys) don’t have a thumb. They
still have the bones of the thumb, even if very small, but they don’t possess anymore a separated
thumb.
This corresponds to a secondary loss (their ancestors had a thumb, but they lost the usage of it).
Their hands form a perfect hook that allows them to swing from branch to branch
How do spider monkeys compensate for not having a thumb
have a prehensile tail, which may be related to lacking the use of a thumb.
Which primates have claws?
What is another adaptation related to this?
None
Since primate’s opposable thumb allows them to grasp and grip on substrates, on the
contrary to many mammals, primates have nails instead of claws.
Primates also have tactile pads with enriched sensory nerves terminations at the tip of the digits
What is primates’ tendency for an erect posture due to?
What is a possible implication for human evolution?
e due
to their ability to sit on their butt, due to their ability to jump and leap, and due to their standing
habits for some of them (e.g. gibbons, chimpanzees and bonobos).
most primates already show some forms of pre-adaptation for bipedalism.
What is the importance of the presence of a clavicle in primates?
It allows them to move their arms and shoulders away from the body.
Clavicle constitutes a pre-adaptation for intense tool use, such as nut cracking, a behaviour observed in chimpanzees, capuchins and macaques
What is the locomotion of lemurs? Give another primate with this mode of locomotion
clinging on tree trunks and leaping from branch to branch.
Galagos
Which primates are brachiating
Which hang
eg gibbons and spider monkeys
eg orang-utans and some lemur species
How does body size relate to mode of locomotion in primates
the body sizes of primates determine which kind of
substrates they can use.
Small primates can then be arboreal, either walking on four limbs or jumping and clinging, while larger arboreal primates like orang-utans tend to hang on large substrates like large branches.
Orang-utans also use the flexibility of tree trunks to save energy when
moving in the canopy.
Some primate species spend most of their time on the ground, being terrestrial, where they most of the time walk as quadrupeds. Others live in trees but prefer a
suspensory mode of locomotion (e.g. spider monkeys)
Name some omnivorous primates
What different foods can they eat
baboons, patas monkeys and chimpanzees.
They eat mostly fruits, but also leaves, seeds, nuts, insects and sometimes meat.
Do any primates have dietary specialisation?
Yes reflected in the shape of their teeth
Give 3 types of dietary specialisation in primates and how this is reflected in their anatomy. Name some species of each
Frugivore primates eat mostly fruits (e.g. most of cercopithecines as macaques and arboreal forest
guenons).
Folivores, eat mostly leaves and grass, like all colobines but also gorillas.
Folivore dietary specialisations are not only reflected in the teeth, but also in the structure of the gut In particular, colobines, who eat lots of leaves, have a stomach with several chambers,
just like ruminants.
Many prosimians are insectivore.
Comment on primate senses
Primates rely much more on vision than olfaction; they display morphological adaptations on their skull, eyes and brain related to this reliance on vision.
What is special about primate sight
A particular adaptation is that primates see the world in colour (trichromatic or dichromatic ).
Primate vision is also different from other mammals as they can see in three dimensions, due to their stereotypic vision, which is enabled by forward facing eyes. This stereotypic vision allows the right and left visual field to cross, enabling a vision in three dimensions
What is the importance of stereotypic vision in primates
allows them to thrive in trees and to adopt an arboreal
life; it also allows them to catch mobile insects and preys by sight
What is the importance of reduced reliance on olfaction in primates
reflected in their morphological facial features, with a reduced snout. Most primates have a relatively flat nose
How do prosimians and anthropoids differ in facial structure
Prosimians still rely a lot more on smell and they have a prolonged muzzle and less forward facing eyes.
anthropoids have a shorter snout and much more forward-facing eyes.
How is reduced reliance on smell reflected in primate brain structure?
eduction of the
olfactive lobe in monkeys as compared to prosimians, and even more reduced in chimpanzees
compared to monkeys.
What consequences does the slow life history of primates have on their behaviour and living systems?
: a long period of growth and maturation requires intense maternal and parental care, as well as a great dependence on flexible learned behaviour (e.g. peering behaviour of young orangutans who take years to learn everything by observing their mother and older siblings).
A consequence of the dependence on flexible learned behaviour is that most primates live in groups, with other group members from who they can learn, and most primates are diurnal.
What are the consequences of a slow life history on primate relationships (3)
primates live in stable groups;
they form long-term relationships similar to friendships, allowing them to reciprocate and cooperate (e.g. sharing food);
overlapping generations live together, opening opportunities to learn socially from older individuals, leading to the emergence of animal cultures.
Where do we find primates?
all primate species are located in tropical and subtropical areas, in Africa, in Asia and in South-America all the way North to Mexico
in general primates (including humans) are tropical species.
Name some northern primates
e Japanese macaques, who can survive to hard winters due to their specific thermoregulatory behaviour (hot springs bathing and huddling behaviour).
Where do most primate species live
75% of living primate
species are located in only 4 megadiverse countries: Republic Democratic of Congo, Madagascar,
Brazil and Indonesia.
Which are the most primitive primates?
What suborder are they part of ?
Lemurs, loris and galagos are the most primitive
primates, of which the last common ancestor with humans goes back to more than 60 million years
Strepsirrhinii
In what order did diifferent primate groups emerge from primitive to derived
Strepsirrhinii Tarsiers (forming part of the prosimians) Platyrrhines Old World monkeys Lesser apes apes (these 3 are the Catyrrhines)
What are the anthropoids
Catyrrhines and Platyrrhines together
What are the Haplorrhini
, the group where Anthropoids and tarsiers are together
Describe some of the prosimians that live in Madagascar
include the lemurs (e.g. arboreal ruffed lemur and terrestrial ring-tailed lemur). Prosimians also include the aye-aye, with their specialised finger to fish on insects and gum in tree holes, and the smallest living primate on earth, the mouse lemur.
Do any prosimians live outside of Madagascar
Yes
in Africa and Asia, but not in the Americas. They include the antwantibos, pottos, bushbabies (galagos) found in Africa the lorises found in Asia. All of these prosimians living outside of Madagascar are nocturnal
Where are tarsiers found?
Give 3 facts about them
only in South-East Asia.
They are tiny nocturnal creatures, and are extremely vulnerable to the pet trade in these regions
What are the key characteristics of prosimians
Do all lemurs adhere to these characteristics?
Small body size
Mostly solitary
Males home-ranges larger than and encompass female‘s
Still rely a lot on smell
Mostly nocturnal
Eat insects and fruits
some species of lemurs live in groups, during the day, and display a female dominance over the males
Name an extinct prosimian that was not small
giant lemurs
Where are Platyrrhines found
South America and South of Mexico
Name 2 platyrrhines with an atypical reproductive system
the marmosets and the tamarins
they are cooperative breeders, where members of the group help raising the offspring of a dominant
couple or of a dominant female
Name a New World Monkey famous for tool use
Capuchins: „chimpanzees of America“
What are the key characteristics of Platyrrhines
Variable body size
Group-living
Often cooperative breeders
Mostly diurnal (a h few species living at night (owl monkeys))
Dichromatic vision
Variable social systems (polyandry, harems,
multi-male multi-female)
Demonstrate the range of sizes in Platyrrhines
marmosets and tamarins being quite small but spider monkeys can be up to 15kg.
What are the Catyrrhines
(old world monkeys)
include Ceropithecines and Colobines
What species do we find in the Catyrrhines
baboons and assimilated species like the mandrills, but also the macaques and the langurs.
Are all old world monkeys cercopithecines?
no
also include eg langurs and colobus
Give the characteristics of Cercopithecines and Colobines (4)
variable sizes and live in groups of variable sizes
strict hierarchical dominance system (often female philopatry)
variable social systems, from harem systems to multi-male multi-female systems.
They are strictly diurnal
What is female philopatry
females born in a group stay in that group while males emigrate when they are sexually mature
What is the diet of colobines and how is this reflected in their gut?
Describe their social system
folivores - have a stomach with several chambers like cows
live in harem systems and infanticide is
common and a high risk for females
What is the social systems of Cerocpithecines?
What is their diet?
Any dimorphism?
multi-male multi-female societies
mostly frugivores and omnivores,
females present exaggerated sexual swellings when they are receptive
Which primates don’t have tails
apes
Name 2 lesser apes
Gibbons and siamangs are the lesser apes.
Where do lesser apes live
only in Asia
Give 6 key features of lesser apes
Give something they are famous for
no tail,
monogamous,
both male and female disperse at sexual maturity,
strictly diurnal
their locomotor mode is brachiation.
They are famous for the duet singing
Where are Great Apes found (other than humans)
Africa and South-East Asia
Give 2 key features of great apes
no tail,
strictly diurnal (even if some populations may be quite active at night like some Ugandan chimpanzees doing crop raiding during nights of full moon).
Give an overview of the different social systems of great apes
social systems go from semi-solitary for orang-utans to multi-male multifemale societies for bonobos and chimpanzees, while most gorilla populations are living in one-male
units (harems).
Bonobos and chimpanzees have a female dispersal system.
Female bonobos are codominant with males, while chimpanzee males are dominant over the females
Give the social system, dependency period and location of orang-utans
Semi-solitary
Long dependency period
Borneo + Sumatra
What is the social system of gorillas?
Which sex disperses?
Is there any dimorphism?
Harems
Multi-male multi-female
Male and female dispersal
Strong sexual dimorphism
What is the social organisation and hierarchy of bonobos?
Which sex disperses?
multi-male multi-female
co-dominant
female dispersal
What is the social organisation and hierarchy of chimps?
Which sex disperses?
multi-male multi-female
male dominance
female dispersal
Give 3 definitions of adaptation
Adaptations: characteristics that improve an organism‘s chances for survival and/or reproduction
Adaptations: functional traits passed down through the next generations
Adaptations: maintained through evolution and selection
Use the example of peppered moths to explain natural selection
2 phenotypes: black or white
like to hang out on the bark of white birch trees.
Before the industrial revolution of the 19th century, most of birch trees had a white bark, and the two
types of moths had a distinctive advantage toward predators: the black ones were very visible, while
the white one could hide on the bark. Then came the industrial revolution which emitted a lot of
black smoke in the atmosphere. These particles accumulated on the bark of the surrounding trees, so
that at the end of the industrial revolution, most of the birch trees were black. Researchers noticed
that, over time, there had been a change in the proportion of each type of moths. White ones were
the majority before industrialisation, and black ones a minority. These numbers got reversed as the
trees became black. In this example, the selective pressure corresponds to the predation by birds, in
combination with a change in the habitat.
What are the 2 types of selection pressure
biotic and abiotic
What are the different types of abiotic selection pressure?
climatic (eg white fur of snow leopards to hide in white snow0
habitat (eg camouflage to hide in leaves etc)
substrate (eg transition between aquatic and aerial
environment. Here, organisms (e.g. razor clams) have adapted to a transitory environment, so that
they can live under water but also survive when the water retreats.)
What does biotic selective pressure include
food (e.g. Darwin finches);
predators;
diseases;
other species living in the same environment (e.g. hyenas who specialised in scavenging and group-living to compete with lions);
conspecifics (individuals from the same species).
When do conspecifics act as a selective pressure
in situations where individuals are attracted to each other (e.g. reproduction) and when individuals compete with each other (e.g. dominance, feeding competition, mating competition, etc…).
Give 3 key methods of selection
natural selection
sexual selection
genetic drift
Give an example of when genetic drift can occur
Genetic drift occurs when a parental population suffers from a bottleneck (only few individuals survive), like after a volcanic eruption. This bottleneck randomly selects few individuals which then compose the parental population of the next generations, leading to a different distribution of characters in the population, as compared to the original population before the bottleneck event.
What are 3 important principles of evolution
variation in traits
heritability of traits
selective pressure
Are behaviours determined by genes or the environment
both
behaviours have a genetic
component, but environment affects the expression of these behaviours
On what 3 levels can we consider the environment
ancestral environment,
a developmental environment,
an immediate environment
What 2 aspects determine ontogeny
developmental environment and genes
How do the 3 levels of environment interact
the evolutionary past of a species, at the population level, determines the genotype (the assemblage of different genes which have been selected throughout the evolutionary history of a species).
Together, genes and developmental environment (which can be for example, parental care, or viviparous gestation) determine the ontogeny.
In turn, the
developmental schemes of an individual will determine, for example, how the brain functions, how
organs function, and all the hormonal system. Those are directly responding to immediate stimuli, or immediate environment.
Summarise what behaviour is in evolutionary terms
behaviours are adaptations enabling individuals to maximise their fitness
How are behaviours seen from an evolutionary perspective?
behaviours are
seen as being optimal and conditional on the current environment. The optimal aspect of a
behaviour is measured by measuring the costs and benefits of such behaviour. When benefits
outweigh the costs, this behaviour is maintained. Conditional means that a behaviour responds to
the current needed conditions and environment
However, behaviours can be constrained, in
particular by phylogeny - some behaviours or physical traits are issued from a long evolutionary past, they show a strong inertia and they don’t respond to current local conditions, but rather to past environmental conditions.
What are the principles of phylogenetic constraints?
species close to
each other tend to have similar characteristics;
that when the phylogenetic signal is strong, closely related species exhibit similar traits;
biological similarities decrease as the evolutionary distance between species increases. Some traits, either biological, physical or even behavioural are constrained by phylogeny
What important study examined the phylogenetic signal of different Primate traits?
What did they find?
Kamilar & Cooper, 2013
looked at phylogenetic signal across 31 traits in primate species.
High signal for brain size and body mass.
(brain size of a given species is closer to the brain size of related species, even if local environment differs.)
Moderate signal for canine sexual dimorphism and for territoriality.
Low signal for traits related to social systems and sociality, such as group size and group composition
Why were the results of the Kamilar and Cooper (2013) study surprising?
previous studies had showed that some primate social systems have a strong phylogenetic component
eg Eulemurs: similar social organisation characteristics
independent on
local habitat conditions Fleagle & Reed, 2013
This variety of contradictory results
shows that we need more research to understand the influence of ecology and evolutionary past on
social systems.
Give 5 costs of living in groups
Competition for food Competition for mates Competition for space Disease transmission Infanticide
Give an example of disease transmission in apes who live in groups
leprosy in wild chimps in Tai National Park and in Cantanhez National Park
Hockings et al. 2021 determined it was caused by M. leprae and followed the disease progression of advanced leprosy - may be from contact with humans
Give 6 benefits of group living
Searching for food
Mating opportunities
Reduce predation risks (dilution/ confusion effect)
Friendships – social bonding
Competition with other groups (eg Gombe Chimpanzee War as described by Goodall 2010)
Social learning opportunities
what is the social system of a species an outcome of
its social structure, determined by size and composition of a group as well as social organisation
Define social organisation
Social organisation is defined by how the individuals are organized, which is determined by the patterns of spacing, by agonistic and affiliative social interactions, by philopatry (whether one or both sexes remain in their natal group), and by dispersal (whether one or both sexes move to a new group to reproduce)
What kind of dispersal system do the least gregarious primates have?
solitary dispersed social system
Describe the solitary dispersed social system
What traits do these primates tend to have
adult male’s territory overlaps the territory of one or more adult females, but each individual forage
alone and maintains social contact through vocal and/or olfactory communication
often nocturnal, foraging at night and sleeping in trees during the day. The mating system in
these primates is usually polygynous
Which primates have a solitary dispersal social system?
Which species stands out?
galagos, lorises, some lemurs, some tarsiers, and orangutans.
Orangutans are the only anthropoid primates with a solitary social system, and they are diurnal
Describe a pair bonded social system
one adult male and one adult female form a small social group and defend a territory against other pairs
usually monogamous (though extra-pair copulations have been observed)
the male usually participates in offspring care (unusual for males in mammals)
Which primate species are pair bonded
This social system is found in Titi monkeys, owl monkeys, some callitrichids (marmosets and tamarins), and many hylobatids (gibbons and siamangs)
Describe One-female multi-male groups.
characterized by cooperative breeding, where
only one dominant female breeds, and other individuals help in raising the offspring.
the dominant female suppresses the reproduction of any subordinate females via aggression and/or pheromonal (olfactory) signals. Usually there is more than one breeding male, thus the
mating system is polyandrous, a rarity among mammals. Some or all of the individuals in these
groups participate in offspring care and this social system is thus often called cooperative polyandry.
Which primate species are one-female multi-male
many marmosets and tamarins
How common are one-male mating systems in primates
i.e. harem system - one of the most common primate social systems
Describe harem systems in primates
A single resident adult male defends a group of usually philopatric related females from other males and, while his tenure lasts, that single male enjoys exclusive mating access to those females, resulting in a polygynous mating system. These groups are always at risk of takeover by non-resident males, who typically form all-male groups, or bachelor groups, while awaiting their chance to become a resident male.
What usually accompanies takeovers in primate harem systems?
What effect does this have?
infanticide
bringing the mothers back into oestrus (sexual receptivity) sooner than they would have otherwise
What is a key physical feature of individuals in harem systems
due to high male-male competition in these species, strong sexual dimorphism between males and females is observed
In which primate species is harem systems found in (5)
most colobine monkeys,
most guenons,
patas monkeys,
howler monkeys
typical of most gorilla populations.
Describe multi-male multi-female social systems in primates
multiple individuals of each sex form large social groups in which the mating system is usually polygynandrous
These are the largest groups of primates, and usually quite complex socially, with differentiated social and kin relationships among group members. In most of these species, females are philopatric and males disperse. The fact that females stay in their natal group allows the construction of female dominance matrilines
What physical aspects are often associated with individuals in multi-male multi-female groups
living with many reproductive males results in females presenting exaggerated sexual swellings when they are receptive, to confuse paternity, to reduce male coercion and potentially to bias paternity toward dominant males.
Which species have multi-male multi-female systems
d macaques, most baboons,
vervet monkeys, mangabeys, capuchins, squirrel monkeys, woolly monkeys, and some colobine
monkeys, as well as some lemurs - most notably the ring-tailed lemur and sifakas.
Describe fission-fusion communities of primates (3)
less cohesive than typical multi-male multi-female groups.
occupy
very large home ranges and individuals form temporary sub-groupings and foraging parties that split and merge over time, depending on changes in resource availability and female reproductive
condition.
typically characterized by female dispersal and male philopatry
Name 4 types of primate that have fission-fusion communities
chimpanzees, bonobos, spider monkeys, and some other ateline monkeys
What is the most complex type of social system?
Which species are characterised by this type of society?
multi-level society (AKA hierarchal or modular society)
These multi-level societies characterize hamadryas baboons, geladas, snub-nosed monkeys, and a few other mammals eg
elephants
What are the 3 levels of a modular society
the one-male unit (OMU),
the band,
the troop or herd
Describe the OMU of a multilevel society
OMU is the reproductive unit and consists of one “leader” male, sometimes a follower male, and several females
Describe the band level of a multilevel society
the band is the ecological unit that forages and sleeps together
Describe the troop/ herd level of a modular society of primates
the troop or herd is a temporary aggregation at a sleeping site or foraging area
What is unique about the hamadryas baboon multilevel society
. In hamadryas baboons, there is a fourth layer between the OMU and the band, the clan, which consists of OMUs and bachelor males linked by social bonds and possibly kinship among males.
What is special about the multilevel society found in geladas
bachelor males join together to form all-male groups
What type of reproduction/ marriage system is seen in multilevel societies in primates?
What does this lead to?
usually polygynous (dominant male from OMU have priority of mating access over several females),
OMUs are always at risk of takeover by bachelor males, who may commit infanticide after taking over females with young infants
How is dominance achieved
through aggression or age
How do female and male hierarchies interact generally in primates
Often, hierarchies among females are separate than hierarchies among males, who all are dominant over the females
Give an example of an indirect fitness advantage of being a dominant individual
How was this studied?
eg having a better access to food resources.
time spent by female
vervet monkeys at feeding sites as function of their rank:
High ranking females manage to spend more time per food patch than subordinates. Similarly, in the same population, high ranking females enjoy spending more time foraging and feeding without having to move places, while subordinates are moving much more while foraging, probably because of displacement by higher ranking individuals
Why is getting more food important for reproduction
Getting more food is important for reproduction, as it guarantees a better physical condition for pregnancy, hereby consisting on indirect fitness advantages.
Give an example of direct fitness advantages bestowed by dominance
survival; reduced IBI
van Schaik (1999) found a dominant female was more likely to survive at any given age
General biological principle: survival decreases with age.
Effect of rank: higher ranking females are more likely to survive than lower ranking ones
Why are higher ranking females are more likely to survive than lower ranking ones
better body condition, but also to a reduced vulnerability to predation due to a higher centrality in the group.
What did Kerhoas (2014) find relating to female survival (3)
in Macaca nigra (the selfie monkeys), higher ranking is associated with a better survival of infants
No matter the rank of
females, living in a large group is beneficial for the infants, probably due to reduced vulnerability to
predators. Also, living in times of high rainfall increases infant survival, due to better food availability.
higher ranking females enjoy a higher infant survival than lower or
middle ranking females
Discuss IBI and dominance rank in gorillas
Wright (2020)
Inter-birth intervals are shorter for
high ranking females.
Discuss male dominance rank and number of offspring in baboons
high ranking males sire more offspring than lower ranking males
Alberts (2006)
Are the fitness advantages of dominance across primate populations?
No
eg in some species it may be a better strategy to increase the length between each birth, to make sure that the current offspring
survive, while in other species reducing the interval between birth corresponds to a fitness advantage.
What is the naïve group selection hypothesis?
In this theory on infanticide, infanticide is considered a pathological
unusual behaviour, which occurs in conditions of human disturbance, and in conditions of high
population density.
in high population density, infanticide is a way to regulate
populations
What does the data say about the validity of the naive group selection hypothesis?
If this theory is true, we should expect that infanticide occurs only in populations living in high population density and in areas of high human disturbance. However, data reveal that this theory is not valid, as infanticide occurs also in low population density, and is common in natural populations not disturbed by human encroachment.
What is the evolutionary theory of infanticide in primates?
Proposed by Hrdy
infanticide is an adaptive strategy that increases male reproductive
success
According to Hrdy (1977, ‘79), how does infanticide increase male reproductive success
What predictions can be made if this hypothesis were true
increases the speed of reproduction, in particular in species with female lactational amenorrhea and in species where males tenure is short due to high turnover of alpha position.
Once an infant is killed, females, who were not fertile with a lactating infant, resume cycling and thus are immediately available for reproduction.
Second, infants of other males should be targeted, so it should be done by new males, and without prior mating by these males with the targeted female. This goes in link with short-male tenure in species where males’ turnover is common.
third, it should occur in species where the chances to sire the infants are
high, so in species with only one adult male, or by dominant males
These predictions are found to be true in the data
In what type of species of primate is infanticide common
Give the relevant study
n in species with only one adult male, as well as in species with several males but only one reproductive adult male like howler monkeys.
Hirawai-Hasegawa, 1988
How can females reduce risk of infanticide
females can confuse the paternity, ensuring
that the males don’t know whether they are or not the father
Increasing association with males
How can female primates confuse paternity
Promiscuous mating
Synchrony of reproductive cycles
Post partum oestrus
How are multi-male multi-female systems thought to have arisen
female promiscuous mating to increase paternity confusion
What did Zinner et al., 1994 show regarding synchronous cycles
What does this imply
When several females cycle together, the
chances of the alpha male to be the father are reduced. Given that this male is supposed to be the only reproductive male, it means that females actually mate with other males. In fact, when several females are receptive in the same time, it is impossible for a single male to keep access and guard these females.
So, cycle synchrony helps confusing paternity
What did Van Schaik & Kappeler, 1997 show about postpartum oestrus
in species where a post-partum oestrus is present, lactation is reduced and infanticide does not occur.
While in species where lactation period is longer and don’t present post-partum oestrus, infanticide
is common.
This study showed that a reduction of lactation period is necessary in order to develop of
post-partum oestrus, which is costly in energy to produce, but it drastically reduces the risks of infanticide
What does paternity confusion ultimately aim to achieve
Confusing paternity is a strategy that aims at protecting the current investment in reproduction for females, by reducing the possibilities that their current infant gets killed
What did Palombit 1997 show about female counterstrategies to infanticide
What is the aim of this behaviour
study on baboons
once an infant is born, females increase their time in proximity with males, who most likely are potential fathers, to search for protection against other males. In contrast, after the death of an infant, they decrease the time spent in proximity, as if they don’t need protection anymore.
increasing proximity with males consists on a way to protect the current investment in reproduction.
Which female counterstrategy to infanticide is thought to have led to the formation of monogamy and pair bonding in primates
increased association with males
This increase of male-female association as a form of protection against infanticide is thought to be a strong driver of the formation of pair-bonds and monogamic social systems
Which female counterstrategy to infanticide is commonly seen in gorillas
simply to reproduce with a new male after the death of an infant (then giving priority to the next reproductive investment).
This behaviour occurs in gorillas, who live in one-male
systems with several females. When a new male takes over the group and kicks out the current male, the babies get killed and all the females reproduce with the new male
What is social bonding
the formation of long lasting, stable and reciprocal relationships between individuals of the same group (i.e. friendships)
Are humans the only species to form friendships?
No
There are increasing evidence in primates, but also in other species like horses, killer whales and humans, that forming friendships carries substantial fitness advantages.
What did Silk 2009 find regarding social bonding?
What did Silk find in a paper published a year later?
female baboons form social bonds and associate more with related individuals, which makes sense from a kin selection perspective
females who are more social, who have more long-lasting social bonds increase the chances of survival of their offspring
In the same baboon population, t females with long-lasting stable and strong bonds have better chance to survive
What are some possible reasons for the increased survival of more social primates
probably due to a higher centrality in the group, better support by friends during aggression, a reduced stress and a reduced probability to be eaten by a redator due to higher centrality
Why are data often focussed on female rather than male baboons (eg in Silk, 2009, 2010)?
Does this differ for different species?
We are able to obtain such long-term data on female baboons because they remain in their natal group, while males disperse.
Yes - in wild chimpanzees, where males stay in their natal group, we can study the long-term effects of friendships
What did Feldblum et al., 2021 show regarding chimp friendships
In male chimps, subordinates who form strong bonds with the alpha male have better chances to become father. Here, tolerance with friends and long-term reciprocity in cooperative action probably plays a big role.
Give 2 reasons why chimp males form coalitions
to reinforce their position in the hierarchy,
also to undertake collective actions such as hunts and border patrols.
What do data from Gilby 2013 show
In male chimps, individuals who are better connected -
who form coalitions with more individuals - have more chances to sire offspring.
Also, interestingly, this study showed that coalition partners are carefully chosen: males pick partners who are not
involved in other coalitions, suggesting a form of trust with partners.
What does R selection correspond to
o an evolutionary reproductive response to a certain type of life history traits, such as a short lifespan and high mortality, in which the best reproductive strategy consists on investing in numbers of offspring but not investing into any form of intense parental care.
When does K selection occur
K selection occurs in situations where lifespan is long and mortality is low.
In this case, the best reproductive strategy is to invest less in numbers of offspring, but rather spend available energy in investment in parental care or in current development.
Are trees under K or R selection?
How is this the case?
long-life plant species are under K selection
the is no parental care stricto-sensu, even if growing protective parts around the seeds can be considered as such investment, but a large part of the energy available is devoted to the current development.
Does r/K selection differ within species
yes - eg humans, also between sexes
Females are under K selection while males are under R selection. Males produce a lot of spermatozoids with little energy reserves, while females produce few ovules with a lot of reserves.
What are methods generally of intrasexual selection
by intimidating, deterring or defeating same sex rivals
What is intrasexual selection
the competition for sex between members of the same sex.
How does intersexual selection act?
What are the constraints?
by making an individual attractive for members of the
opposite sex.
acts through differing reproductive strategies between opposite sexes, herby creating
sexual conflicts
constraints to gain access to mating partners - mate choice
What ultimately counts for any reproductive strategy?
maximise the lifetime reproductive success.
Simply, what is the difference between male and female reproductive strategies in primates?
What does this result in?
males are ready to mate pretty
much at any time, while females much less, since they are constrained by physiological requirements
such as gestation and lactation, and by potential parental care
for males, the number of available receptive females is limited, while the number of males available for females is constant.
In consequence, males tend to compete to access to females, resulting in an intense form of malemale competition, while females tend to choose among potential mates
Why are females the choosier sex?
What is the consequence of this
reproduction can be
costly for females, due to gestation, lactation and maternal care
for females what matters is mate choice, rather than competing
with other female to access to mating partners
Give an example of female-female intrasexual competition in lemurs
eg in e group-living lemurs where reproduction is seasonal, resulting in all females from a given group being receptive at the same time.
Give 2 examples of sexual dimorphism in primates that is not body or canine size
vocal apparatus (e.g. vocal sack on the throat of male howler monkeys)
Orang-utan males cheek flanges
Describe the sexual dimorphism seen in the vocal apparatus of howler monkeys
Male howler monkeys use long calls to deter opponents and competitor
Describe the sexual dimorphism seen in orangutan cheek flanges
Cheek flanges in orang-utans only grow at a certain stage in life, and not necessarily at sexual maturity like other sexual characters. Here we talk about developmental arrest, since the full development stops at some point to continue later. Developmental arrest is very rare in mammals, and another example of developmental arrest includes human’s wisdom teeth, that only grow much later after sexual maturity.
How does cheek flange development differ between populations of orangutan
In Borneo, we observe a short delay in the development of flanges (i.e. the developmental arrest is short, they grow the flanges quite fast after maturity). In contrast, in Sumatra, this developmental arrest is much more delayed. In consequence, in Borneo, many males have already their flanges, while in Sumatra, only few males have their fully-grown flanges
What explains the difference in cheek flanges between Bornean and Sumatran orangutans?
In Borneo, males are less able to monopolize females, while in Sumatra female monopolization is
easier.
Monopolization means that a male will roam into the various territories of the females and will limit their access from other males. These differences in monopolization potential are associated with unstable dominance between males in Borneo, where male tenure as alpha is short.
In contrast, in Sumatra, dominance is stable and male tenure longer.
As a consequence of these differences in the competition between males, in Borneo, the best strategy for males is to grow fast the flanges, as it increases their chances of reproduction, given that females tend to choose only males with flanges to mate.
In Sumatra, the best strategy is to wait for a dominant position to grow flanges, delaying their development
True or false
Male-male competition and sexual dimorphism are directly linked to the mating systems
True
What Dixson 2009 find relating to primate mating systems and sexual dimorphism
There is a higher sexual dimorphism in groups with only one male. The mating and social system is here a direct consequence of male-male competition, where males prevent the access to females to other males by producing long calls, enabled by the development of laryngeal sacs and other vocal adaptations.
What did Plavcan 2012 find regarding body mass dimorphism and mating systems
Higher sexual dimorphism (based on body mass) in groups with only one adult reproductive male (polygyny), and in social systems where male-male competition is more intense
What is the main form of male-male competition in primate societies where many males live in the same group?
sperm competition
Describe sperm competition
Since many males can mate with the
females, the sperm compete with each other. This competition is reflected in the size of the testes.
Allometric scaling of the size of the testes for all primate species: some species are below the curve
(they have smaller testes related to their body size), while others, located above the curve, have
larger testes related to their body size.
Chimps are above LOBF for allometric scaling of body size to testes where as gorillas are below line
Chimpanzees have large testes while gorillas have relatively small ones.
males living in multi-male multi-female systems have large testes,
while smaller testes are found in only-one male societies
Why do males living in multi-male multi-female systems have large testes,
while smaller testes are found in only-one male societies?
Large testes reflect a high sperm
competition in multi-male multi-female primate societies.
What do the attractive traits in male primates relate to with regards to female mate choice
resource holding potential.
What is the resource holding potential of males?
the capacity for males to provide protection, against other males, against predators or against other groups; to provide parental care in species where males do so, like in gibbons; to provide resources, or to protect access to resources; and ultimately to provide good genes.
How is resource holding potential usually displayed
honest signals
Use sub-nosed monkeys as an example of honest signals
Black-and-white sub-nosed monkeys, who live in multi-level societies with one-male units including a single reproductive male, have these red lip colours
All males, either juveniles or adults seem to display this bright colour. However, the lip colour of one-male-units (OMU) males undergoes reddening in the mating season, whereas the lips of subadults and juvenile bachelor males become paler at that time of year. In these monkeys, the lip coloration is a badge of (group-holding) status during the mating season, with non-adults undergoing
facial differentiation to avoid the costs of reproductive competition.
Give an example of honest signals from Vervet monkeys
live in multi-male multi-female groups, there are greyish to greenish in colour, with black faces. However, adult males have spectacular colours on their butt. Their testes are blue and the scrotum are red.
Vervet monkey males carry out the red-white-blue display: they lift their tail up to show these bright colours.
more dominant individuals display more often per unit of time their bright colours than subordinate males. Since dominant males tend to have better access to mating opportunities, this signal may serve as an honest signal toward the females to show their group holding potential
Give 3 further examples of ornaments as honest signals
the bright colours of mandrills,
red face of Uakaris
the colour patterns of Douc langurs
How does colour of Mandrills relate to female choice
more colourful males get more mounts than less colourful ones, hereby increasing their chances to sire offspring, with brighter males being
approached by females more than dull males.
t females present more to
brightly coloured males. So, it seems that mate choice occurs and that these bright colours have evolved under the pressure of mate choices by females.
How do the bright colours of mandrills relate to genes
bright colours are related to the health of the individual, as well as to the genetic diversity of their immune system, here relating to the idea of good genes are displayed through honest signals
Where do intersexual conflicts come from
females and males adopt different reproductive strategies to reach optimal fitness.
These conflicting optimal fitness strategies concerning reproduction relate directly to the K and R selections. Sexual conflicts are embedded within an evolutionary arm race between males and females.
What makes male reproduction cheap
How does this compare to females
What does this mean for the limitations on reproduction
under a selection of type R, males invest in numerous gametes without energetic reserves.
e. In their situation, reproduction mistakes, such as miscarriage, are extremely costly. In consequence, females are choosy (mate choice).
Since the amount of receptive female is then limited, males are limited by the access to females
How is the spacing of males and females limited
Females investment is targeted toward their current offspring.
Gestation, lactation and maternal care require a lot of energy, and thus a lot of resources.
Consequently, females are limited in space by resources distribution and availability.
Males, who do not invest into offspring, are much limited by food resources and can search all the time for mating.
Consequently, males spacing is limited by the access to females.
What is the reproductive success determined by?
How do they do this?
by the number of offspring they obtain
Since female reproduction is limited by the access to resources, females compete with each other over these resources. Accessing to better resources enables a reduction of inter-birth intervals, hereby increasing the potential number of offspring obtained across a lifetime; better resources are associated with improved survival, with better offspring survival and with better health.
How do dominance hierarchies form between primate females?
Since female reproduction is limited by the access to resources, females compete with each other over these resources. Accessing to better resources enables a reduction of inter-birth intervals, hereby increasing the potential number of offspring obtained across a lifetime; better resources are associated with improved survival, with better offspring survival and with better health.
As a consequence of this competition for resources, females try to monopolize resources, which leads to the formation of dominance hierarchies
Are positions in dominance hierarchies heritable?
yes The position of a given female within dominance hierarchies is passed on to their daughters, here building matrilines (i.e. lines of female dominance passed from generation to generation), mostly to be able keep a good access to resources.
Describe the variance in reproductive success of females
Why is this?
Low variance and weak reproductive skew
Despite these hierarchies, and since each female is limited by resources but all manage to
have offspring, among females, the variance in reproductive success is low
When is there strong reproductive skew in a female dominance hierarchy
In cooperative breeders, where subordinate reproduction is suppressed by the dominant, the reproductive skew is strongly biased toward the dominant.
Describe the reproductive skew in male dominance hierarchies
since reproductive success is limited by the access to females, there is a high variance in reproductive skew in a given group, with higher ranking males having most of mating opportunities as compared to subordinate males. Consequently, we observe a high reproductive skew in males.
What did Kutsukake & Nunn, 2006 find regarding reproductive skew in male chimps
What did Widdig et al., 2004 show regarding reproductive skew in male rhesus monkeys
when there are more males, less of them have a chance to mate since most mating are taken by the top ranked ones.
males in their prime, between 10 and 13 years old, sire most offspring. In this population, the top sire in each year produced 24% of the infants, while 71% of troop males sired no offspring at all.
What are the 2 key strategies of males to maximise reproductive success
female defense
resource defense
What are the different forms of female defense in primates
long-term associations, as in monogamous pairs or in harem systems, with only one reproductive male
dominance hierarchies, as in multi-male multi-female groups, where dominant males have priority of access to the females, or where males can form short-term consortship bonds with females, and where females are receptive asynchronously
coercion (where males physically force females to copulate)
According to Clutton-Brock & Parker, 1995, when does coercion exist in male primate populations?
When does coercion occur according to Smuts and Smuts 1993?
when males attempt to bias
mating in their own favour by using harassment, meaning by persistent mating attempts; or by using intimidation such as aggressive behaviour; or by forced mating
when males use the force, or threat, leading to higher rates of potentially fertile mating with the female and a lower rate for other potential mates, at some cost to the female
What is the difference between the Clutton-Brock & Parker, 1995 and the Smuts and Smuts explanation of coercion
Smuts and Smuts give greater importance to the exclusion of other males from mating by using the force, while the first definition focusses more on the ways forced mating are obtained
Give 2 primate species where coercion is common
Coercion of females is common in orang-utans and in some baboons, among others.
How do different groups of primates compare regarding commonality of coercion?
What behaviours are common in the most coercive groups?
OWM males are more coercive than NWM, which are more coercive than lemurs
Mating during pregnancy, copulation calls and surreptitious mating are very common in the most coercive groups of primates, the old world monkeys
What is unique about OWM cf. NWM and lemurs
s the multiplicity of cycles per conception, longer mating periods and the presence of exaggerated sexual swellings.
Give an example of females evolving very costly counterstrategies to male coercion
sexual swellings in catarrhines
Give a type of female counterstrategies to male coercion seen in lemurs and bonobos
female dominance over males and the formation of female coalitions.
Compare sex coalitions in chimps and bonobos
n chimpanzees, males form coalitions to aggress other males, while in bonobos females form coalitions against male aggressions.
What did Tokuyama & Furuichi, 2016 find regarding bonobo coalitions (5)
Femalefemale coalitions are very common, much more than male-female and male-male coalitions.
at all ages, but especially for young females, forming coalitions increases the chances to win a conflict.
All of the targets of female coalitions are males, of which most (95.5%) are adult.
Females never formed coalitions to attack other females.
when females formed coalitions, 100% won against a target males.
Give the cyclical flow of the arms race between the sexes in primates
from the males, their capacity to recognize kin (family members) and mechanisms to detect ovulation lead to high chances of infanticide, which are counterbalanced by females mating with multiple males.
This strategy is then challenged by males who use mate guarding, by an intense sperm competition, by intimidation, punishment and coercion;
these male behaviours are then counteracted by females who increase the length of mating periods, conceal their ovulation, show synchronous oestrus and form female coalitions
What is the main source of required energy in primates
carbohydrates
Give 3 examples of toxins in human diet
tannins
caffeine
alkaloids
Where do primates obtain
a) carbs
b) fats and oils
a) from fruits, seeds and gum.
b) extracted from seeds an animal prey
Where do Primates obtain proteins
from leaves, in particular young leaves which are high in protein content and low in fibre content. Proteins also come from arthropods, such as insects and spiders, and from other types of animal prey
What is geophagy
Is it common?
licking earth elements, such clay or rocks, to get essential salts from them
Geophagy is a common behaviour for many species of animals (e.g., community of parrots in Peru). Several species of primates have been observed licking rocks or eating clay (e.g., macaques and mangabeys).
Where is water found in a primate’s diet?
Give an example of where water is particularly inaccessible
in food, in tree holes and in natural water holes
In some environments, where water on the ground is rare, some primates like chimpanzees in Comoé, a savannah National Park in Ivory Coast, have developed a tool technology to access to water in tree holes.The tip of a branch is chewed on the produce a type of sponge, enabling the individuals to dip into tree holes to extract the residual water. Other chimpanzee populations use leaves to make a sponge out of it and to extract water.
Give examples of chimps using tools to extract foodstuffs
Tools, such as long sticks, can be used to extract underground honey, as it has been observed in Gabon.
also extraction of termites and ants
use of wooden or stone hammers to crack nuts
How long have chimps been using tools for nutcracking
These nut cracking techniques have been used for thousands of years, and researchers studying these techniques in wild chimpanzees can see in other extracting techniques, such as pounding techniques, examples of proto-cultures that most likely preceded the use of wooden or stone hammer to extract food
Apart from using tools, what part of primates’ repertoire can be used to access and extract food
adapted colour and stereotypic vision
Since they see in three or two colours, they can distinguish the various degrees of ripeness of fruits, and with their forward-facing eyes, they see in 3D which enable them to move in the trees and capture moving preys.
A certain number of morphological adaptations facilitate food extraction and processing, such as teeth shapes adapted to certain diets, or the specialized finger of the aye-aye to extract gum and insects under bark trees and tree holes.
What are some pros and cons of a fruivore diet
. Fruits are a great source of sugar and carbohydrates, but the problem when you rely a lot on fruits is that their production is relatively patchy
also seasonality in production
variability between years - highly unpredictable
What can seasonality of fruit production be due to
seasonality in production is, in some parts, due to variation in rainfall and temperature, even in tropical areas, but also due to natural cycles of production of each species of tree
Why are fruits easy to monopolise in the Tai National Park in Ivory Coast
For some months not so many species are fruiting, while in other
months a lot are fruiting. This then has consequences on the dynamics of primates that rely on these
sources, and it makes these resources easy to monopolize
What nutrients are leaves good for
However what can they also contain? How have folivore primates adapted to deal with this?
protein
fibre
tannins, which are hard to digest
developed a specialised stomach with several chambers helping the digestion.
What is a benefit over folivory vf. frugivory
leaves are relatively evenly distributed: leaves are produced in large quantities, which makes them hard to monopolize. In addition, leaves show a relatively weak seasonality, or no seasonality at all
What nutrients do insects and arthropods provide
protein
fat
Which elements of prosimian anatomy is used to help catch moving insects
their leaping mode, great vision and their well-developed auditive system
True or false
Very few primates each arthropods
False
Since arthropods are a great source of protein and fat, most primate species eat insects and arthropods
Describe the habitats of Ihoest and blue monkeys
these two monkeys, which are sympatric (i.e., they live in the same forest), occupy different parts of the forest: blue monkeys, larger than the lhoest monkeys, occupy the top part of the canopy, while lhoest monkeys occupy the lower strata.
What is the most common antipredation strategy in primates
group living
How does group living act as an antipredation strategy
Once in group, chances to be caught by a predator are reduced due to the higher number of potential targets (dilution effect), due to a confusion effect when individuals flee in many directions (confusion effect), and due to alarm systems given by conspecifics
How do primate sleeping habits act as anti-predatory
Primates have also learned to adapt to the risk inherent to predation by using typical sleeping habits, such as building nests high in the trees for the apes (except for gorillas who do their nest much lower due to their weight, but their large body size also protects them against predators, even if the youngsters build nests higher than adults)
Other primate species, like some lemurs in some regions of Madagascar and gelada baboons, sleep on cliffs to escape predators
What do alarm calls in primates achieve
deterrence of predators s and to inform conspecifics from their group, as well as other animals in the surroundings such as other primates living in polyspecific association
Give an example of polyspecific association between primates and non-primates
small antelopes associate with terrestrial primates like mangabeys, probably for taking advantage of the number of individuals to detect and avoid predators
Name 7 predators of primates
Snakes Birds Cats Humans Fossa Komodo dragons Dogs
Give an example of primates having different alarm calls for different predators
Arnold & Zuberbuhler, 2006
Putty-nosed monkeys possess a referential call system.
Different call for eagle and for leopard
Describe different responses to referential alarm calls in guenons and vervet monkeys
when hearing or seeing a leopard, guenons and vervet monkeys use a referential alarm call and they tend to climb into trees, or to climb higher for guenons. When hearing or seeing an eagle, these primates use a specific referential call and they rush toward the ground or in bushes for vervet monkeys, while guenons go lower in the trees, under big branches. These primates also respond differently, acoustically and behaviourally, in presence of a snake
What is socio-ecology
a heuristic approach that attempts to explain all forms of primate social organisation, would it be grouping patterns, dispersal patterns and even social relationships.
What is the idea of the selfish herd
the idea that aggregations of animals could occur simply as a result of
animals’ attempts to avoid predation by putting conspecifics between themselves and the predator -
Sum up the idea of parental investment
the idea that the sex investing less in offspring evolves to compete for access to the other sex, while the sex that invest a lot in offspring, in term of gamete production, gestation, lactation and parental care, is constrained by energy requirements and thus compete for food.
What does primates socio-ecological models attempt to stablish
Causal relationships between food distribution, predation, mating strategies, social organisations and relationships
What was one of the earliest models that attempted to link ecology an social organisation?
What did this propose?
Crook & Gartland, 1966
proposed five grades, separated by group sizes, mating structure, male dispersal, sexual dimorphism, territoriality, but also with variation in grades based on differences in habitats, diel activity (either diurnal or nocturnal) and diet
This model sets the
bases for further models emphasising on predation and food as determining social organisations. In this model, social conditions present in each grade were mostly based on ideas of sexual selection and male-male competition for access to females.
Which primates does grade 1 in the Crook and Gartland (1966) model include
What assumptions are included in this
grade one includes most of Prosimians, living in forest habitats, eating insects and being nocturnal.
Here, the assumption is that insects are easier to prey upon for solitary nocturnal individuals.
Which types of primate species are included in grade 5 of the Crook and Gartand (1966) socio-ecological model
Grade 5 includes species living in the savannah and being diurnal.
Here the assumption is that, in savannah habitats, there is enough food to sustain large groups and that large predators oblige primates to aggregate in these large groups
How does habitat, diel activity, group size, and sexual dimorphism differ across the grades in Crook and Gartland (1966)’s socio-ecological model
Habitat: grades increase from closed to open, going from forest habitat toward savannah and grassland.
Same as for diel activity: it starts
with nocturnal species, then crepuscular in grade 2 and then diurnal.
Group sizes also increase from
grade 1 to grade 5.
Same as for sexual dimorphism, from none to high in grade 5
Who proposed the age-graded male-troop model
Give a very brief overview
Eisenberg, Muckenhirn, and Rudran 1972
demographic conditions (maturation and philopatry of natal males) are responsible for observed transitions from single males to multiple males in social groups
What is the cycle of social configurations in primates according to Eisenberg (1972)
the troop growth model, which assumes that the optimal social organisations at moderate population density are one-male units, with a founder male aggregating around few
females.
The troop grows by recruitment yielding a subgroup of juveniles and a beta male that is
subordinate to the alpha male who can be his father.
At greater densities, younger males may form a peripheral subgroup of their own that has no direct contact with the basic subgroup of mothers and their young. Although the troop now appears to be multi-male, Eisenberg and colleagues propose that it would be more correct to consider it an age-graded-male group.
Splitting of the new unstable troop can lead to the original uni-male configuration
What was Eisenberg (1966)’s model of space utilisation patterns and evolutionary trajectories from solitary life to group-living organisation?
starts with a solitary pattern, where adult males and females have separate centres of activity and encounter infrequently. The extended ranges of the males overlap with the home ranges of the females.
Then, there is a transition toward family groups, where a bonded pair and their subadult offspring travel as a homogeneous unit in an exclusive home range.
Family units transit toward uni-male groups where an adult male is in periodic contact with a cohesive group of adult females and their offspring.
These uni-male groups with periodic contact transit toward uni-male groups with relatively constant contact with a cohesive group of adult females and their offspring, which themselves transit toward multi-male groups, which is a cohesive group of several adult males and females with their offspring
What is the main driver for change in social organisations according to the Eisenberg model (1972)
population density
What did Wrangham propose in 1980
What does this model emphasise
What is the importance of predation
the ecological model
emphasizes the fact that females are the ecological sex, in the sense that females distribute themselves around food resources.
For Wrangham, predation doesn’t play an important role in female distribution and primate social organisations.
Describe Wrangham’s (1980) ecological model
Wrangham considers that there are 2 types of female groupings: female-bonded groups and non-female bonded groups. Food is at the base of differences between these two groupings, with clumped food such as fruits for female bonded, and evenly distributed and abundant food such as leaves for non-bonded females.
In turn, these types of food lead to an increase of feeding competition for females when they rely on clumped food, while no competition occurs when females rely on leaves.
To overcome this competition, females aggregate in large groups to compete with other groups in frugivore species, while in folivore species, females will aggregate only around males to search for protection against other males.
So here, grouping in female bonded groups is due to between-group feeding competition, while female grouping in non-bonded groups is due to male mating strategies such as
harassment and coercion.
Within the group, in female bonded groups, inclusive fitness benefits lead
to females giving benefits to their relatives, such as their daughters, while no inclusive fitness
benefits are expected in folivore non-bonded groups. Inclusive fitness benefits make female stay in
their natal groups on one side, while in non-bonded groups females disperse.
And in turn, due to high within-group competition and inclusive fitness benefits, differentiated dominance and grooming relationships are expected in female bonded groups, with the formation of matrilines following kin structure (daughters inherit the rank of their mothers), with dominants receiving more grooming than subordinates and having priority of access to food. Not such differentiated dominance and grooming relationships are expected in non-bonded female groups
What are the 2 types of diet in Wrangham’s ecological model?
What does each diet favour?
: In this model, the influence of food distribution is considered to differ between periods of food abundance (here “Growth diet”) and periods of food scarcity (here “Subsistence diet”)
Growth diets in large high-quality patches, where there is a finite number of feeding sites, favour female-bonded groups. Subsistence diets in uniform, continuous patches, in which there is effectively an
unlimited number of feeding sites, neither favour nor disrupt group-living. Females therefore sort
themselves into groups competing against other groups.
What are the 6 key features of female bonded groups in Wrangham’s (1980) ecological model
Food clumped (fruits)
Increased competition among females
Females form larger
groups to overcompete smaller groups
Inclusive fitness benefits: females related within the group
Philopatry of females
Differentiated dominance and grooming relationships
What are the 6 key features of non-female bonded groups in Wrangham’s (1980) ecological model
Food evenly ditributed (leaves)
No competition
Female disperse from natal group
No differentiated dominance and grooming relationships
Non-female bonded
Females gather
around males for protection against other males
No inclusive fitness benefits
Summarise the ecological model (Wrangham, 1980)
: food distribution is the main basic determinant of female grouping and female social relationships. Food differs in their distribution, in their quality and in patch sizes. Defensible high quality food leads to group formations to fight other groups, defensible but of variable quality food leads to in-group dominance hierarchies. And in both situations, females stay in their natal group (female philopatry). When food is in small high quality clumps such as insects or uniformly distributed such as leaves, competition between groups is less intense, and dominance hierarchies within-groups are weak, leading to female dispersal.
How does van Schaik’s model (1989) compare to that of Wrangham (1980)
van Schaik argued that multi-female groups
were initially favoured by predation pressure.
However, van Schaik agreed with Wrangham that food competition determines female social relationships within and between groups.
van Schaik
introduced for the first time the concepts of contest and scramble competition
What are the 2 contest regimes in van Schaik’s (1989) model
contest competition
scramble competition
What is van Schaik’s (1989) idea of contest competition
resources are clumped,
so resources are scarce and valuable,
hence resources are worth fighting for, because they can be monopolized, resulting in strong direct competition.
What is van Schaik’s (1989) idea of scramble competition
resources are dispersed like insects or evenly distributed like leaves.
Thus, individuals just have to scramble to get enough, resources are not worth fighting over because they are not monopolizable, resulting in the absence of direct competition.
In van Schaik’s model (1989) what determines the nature of female social relationships
How many types are there?
within and between-group food competitions
4 types (Type A-D)
What is type A female relationship in van Schaik’s (1989) model
When scramble competition predominates within groups, females in multi-female groups would develop individualistic, egalitarian dominance hierarchies
What is type B female relationship in van Schaik’s (1989) model
When contest competition predominates within groups, groups of female relatives would develop nepotistic, despotic dominance hierarchies
What is type C female relationship in van Schaik’s (1989) model
Under intermediate or high predation pressure, when foods occur as in Type A, scramble competition would be expressed within groups while contest competition would be expressed between groups (because larger groups suffer less from predation than smaller groups), leading to philopatric females and egalitarian dominance hierarchies
What is type D female relationship in van Schaik’s (1989) model
under low predation pressure, when population density is high relative to the food supply, contest competition between groups would be favoured and female relationships within groups would be nepotistic but with egalitarian dominance hierarchies
What is the importance of scramble competition between groups to female relationships according to van Schaik (1989)
He did not consider scramble competition between groups sufficiently important to affect female social relationships
How was van Schaik’s model adapted in 1997
They assigned new labels to Types A–D, based on the
intensity of contest competition. Importantly, for the first time in the field of socioecology, a
distinction was made between “ecological models” and “socioecological models” because it also
incorporated the social component of infanticide avoidance
Give the amended names of female social labels by Sterck and van Schaik (1997) to van Schaik’s original Type A-D names (1989)
A was now Dispersal–Egalitarian, B was Resident– Nepotistic, C was Resident–Egalitarian, D was Resident–Nepotistic–Tolerant, based on the intensity of contest competition
How does Sterck’s incorporation of infanticide change van Schaik’s 1989 model
They proposed that the risk of infanticide was sufficiently strong that under the conditions of low predation and low competition, females would disperse from their natal groups to form strong associations with protective males, leading to the dispersal–egalitarian groups (like Wrangham’s non-female-bonded type).
When does Dispersal-Egalitarian type occur (Sterck, 1997)
What about resident-egalitarian
Dispersal-egalitarian occur when within and between group competitions are low,
resident-egalitarian when within-group competition is low but between-group competition is high
When do Resident-Egalitarian and Resident-Nepotistic-Tolerant types of relationship occur (Sterck 1997)
resident-nepotistic when within-group
competition is high but between-group is low, and resident-nepotistic-tolerant when both within
and between-group competitions are high.
How do relationships between dispersal, predation, food competition and female relationship act within a cycle in Sterck (1997) model
when dispersal is costly, females do not disperse; high predation risk makes females grouping together; large group size leads to strong within-group contest competition.
This in turn affects female dominance relationships: females form coalitions with kin against other females (nepotistic social relationships).
This in turn prevents female dispersal, which means that groups grow above the optimum size before they eventually split.
Once females are in this cycle they cannot easily convert to the opposite strategy of low within-group competition, egalitarian
relationships, female dispersal and small (optimum) group sizes
When is the benefit of exluding other females from resources a) low and b) high, according to Sterck (1997)
a) when there is no dominance hierarchy, female dispersal is possible and the benefit of excluding females from resources is low;
b) when dominance hierarchy is high with strong kin support, such as forming coalitions with family members, female residence is necessary and the benefit of excluding other females from resources is high.
What did Bernard Thierry, University of Strasbourg claim about socio-ecological models
the attempt to encompass all observed social systems within one single framework is an illusion
What missing assumptions from Sterck and van Schaik’s socio-ecological model (1997) did Thierry (2008) point out
particularly regarding the effect of infanticide risks on female resident groups and the effect of scramble between-group competition.
Thierry lists a series of inconsistencies between what is observed in primates and what the model should predict such as rates of agonistic interactions in several populations not being affected by habitat variations in the patchiness of food supplies, or that female dispersal is associated with clear dominance hierarchies and aggressive encounters between groups in some species, like chimpanzees
What comment did Thierry (2008) make about phylogeny when criticising Sterck’s socio-ecological model (1997)
He based his argument on the fact that some traits are correlated within closely related species living in different habitats and ecological conditions. He used macaque species to illustrate his point: some species of macaques show a high degree of intolerance, strong dominance hierarchies and high nepotism, like rhesus macaques and Japanese macaques. While other species of macaques (e.g., black-crested macaques and Tonkean macaques) are relatively tolerant, with a relaxed dominance and a weak influence of kinship. All these macaques have similar dispersal systems, similar type of diet, similar multi-male multi-female groups, and they may even live under similar climatic conditions.
For Thierry, this weakens the determinism of ecological conditions on social relationships and for him similar levels of tolerance between Tonkean macaques and black-crested macaques are due to the fact they are closely related species, so he argues that phylogenetic constraints play a major role in conservation of dominance systems
What did Thierry (2013) argue about adaptation for ecological vs sociality
some strategies can be adaptive from an ecological perspective, while other strategies may be adaptive from a social perspective, counterbalancing and opposing the advantages due to the ecology.
Thierry argued that some strategies can be adaptive from an ecological perspective, while other strategies may be adaptive from a social perspective, counterbalancing and opposing the advantages due to the ecology. Give 2 examples of this
high contests can be advantageous because it reduces the number of conflicts and shortens duration of conflicts, but also low contests can be advantageous because it increases conflicts resolution and reduces the
severity of wounds;
also, high maternal restrictiveness protects infants against dangers, but alloparental care (care provided by other individuals than the parents) increases the number of protectors.
What did Menard (2004) find about the relationship between ecology and dominance in primates
No evidence of a relationship between today‘s ecological conditions and dominance style
(Menard, 2004)
Give a ecological model of primate social systems that is more conservative and does not attempt to put all elements of primate sociality within a single mode
What perspective does this model take and what does it categorize?
the dispersal/foraging efficiency model. T
Isbell, 2004
perspective of females
categorizes five types of females: stingy mothers, generous mothers, facilitators, indifferent mothers and incomplete suppressors.
According to Isbell (2004) where are a) stingy mothers b) generous mothers c) incomplete suppressors found
Give examples of species in each category
a) Stingy mothers are found in species where only one female reproduces, females don’t share the resources within their home-range, and females disperse from their natal groups. Gibbons, pottos, tarsiers and lemurs fall in this group
b) Generous mothers are found in species where reproductive females are solitary, but they share resources within their home-ranges (so there is home-range overlap) with other females. In general, other females are daughters or related females like aunts and nieces. Orang-utans, mouse lemur, and galagos would fit here
c) Incomplete suppressors are small groups of kin females (related females), where females disperse when chances of in-group reproduction are limited; red howler monkeys and some lemurs would fit in there.
According to Isbell (2004) where are
a) facilitators
b) indifferent females
found
Give examples of each
a) Facilitators correspond to mothers facilitating their daughters’ reproduction, by forming matrilines and where it is then beneficial to not disperse. These are equivalent to female-bonded groups of Wrangham. Yellow baboons and macaques are in this group.
b) indifferent females occur when food does not limit females, where females may disperse or stay in their groups. Langurs and colobines fall in here
Give a summary of Isbell’s (2004) Dispersal/foraging efficiency model
dispersal costs are at the base of it.
Ability to expand the home-range is the next condition, as well as goal direct traveling modes.
Foraging efficiency and female-female feeding competition is then considered to categorize the different strategies
What is feeding efficiency vs foraging efficiency
Feeding efficiency includes only the time and energy spent during feeding;
foraging efficiency includes the costs of both feeding and moving during the day
How does feeding and foraging efficieincy differ between group sizes in yellow baboons
What study is this from
Small groups have a better feeding efficiency than large groups, meaning that their intake per minute is higher. Since there are fewer individuals, each of them gets more than if they were living in a higher group. However, foraging efficiency shows no difference between groups of different sizes, illustrating that moving between food patches seems to be higher for small groups than for large groups or that large groups have access to larger patches of food than smaller groups.
Stacey, 1987
How does foraging efficiency compare between capuchin group sizes
the small group
spend more time foraging than the larger group
Given that large groups have more individuals, they most likely deplete food resources much faster than the small group so large groups have to compensate by moving more
Ruiter 1989
Does food quality differ between group sizes in capuchins
, a cost inherent to a large group is that, when food is scarce, individuals have to rely on food of poor quality
, a cost inherent to a large group is that, when food is scarce, individuals have to rely on food of poor quality. What data demonstrates this?
Ruiter (1989) showed the larger group relies more on poor and risky food (pith of palm stems and snails) during the dry season. Risky because snails are found on the ground, where predation risks are higher. For these
frugivore species, being too big as a group doesn’t seem to be so good
How much time do different sized groups spend eating and travelling in folivore species eg mountain gorillas
as for baboons and capuchins, larger groups spend less time feeding most likely due to competition for food between a high number of individuals
larger groups do not travel more than smaller groups, and the costs of traveling are higher for
intermediate size groups.
Grueter 2018
How does feeding efficiency differ between group sizes in folivores such as mountain gorillas?
The largest groups have the have the highest feeding efficiency
Grueter (2018) showed gorillas living in large groups gain advantages
when it comes to compete with neighbouring groups so the increased efficiency of larger groups may be explained by advantages in intergroup contest competition
How did home range overlap differ between gorilla group sizes
The largest group had much lower home-range overlap than the other study groups which may be due to groups avoiding
one another as a result of male mating competition
Grueter et al., 2018
Simply explain the reasoning behind group living with relation to food distribution
living in groups is beneficial from a foraging perspective, but increasing group size lower these advantages by increasing competition.
advantages of large group size depend on the type of food - gorillas being folivore as compared to frugivore baboons and capuchins - and on the intensity of between-group competition (as in this gorilla population).
Name 4 antipredation strategies adopted by primates
not group living
by hiding from predators, by small and cryptic;
by living alone,
by living
at night,
by forming polyspecific associations (i.e., associating with other species to benefit from
their vigilance, from their alarm calls and from their number).
How does predation risk relate to commonness of group living
What other feature is associated with predation risk
when predation risks are high, primates live
in larger groups (Hill and Lee, 1998)
as risk increases number of males increases
(Van Schaik & Hoerstermann, 1994)
How did van Schaik find out number of males increases as predation risk increases
compared three folivore primate species - howler monkeys,
colobus and langurs.
Monkey eating predation by crowned eagles is also compared, showing that langurs are much less predated than howlers and colobus. When the number of adult males is compared, it reveals that species that have a higher risk of predation also have more males in their groups
(Van Schaik & Hoerstermann, 1994)
What is a cost group living incurs in terms of predation?
How does this help explain which primates live in large groups
large groups are easier to detect than small groups
body size:
when the preys are large and conspicuous, they are easily detected by predators, consequently it pays to form large groups. When preys are small and discrete, they are harder to be detected by predators, so they tend to be cryptic or solitary.
How does vigilance compare between different group sizes of capuchins?
How does this relate to other costs/benefits of group living?
The large group is less vigilant than the small group; the small group never goes to the ground and occupies higher strata than the large group.
large group had a lower feeding efficiency than the small group, but here anti-predation advantages counterbalance the feeding costs
Ruiter, 1986
How do strata relate to group size
small group spends more time in the higher strata than does the large group. Predation risk is higher in lower strata (terrestrial predators), so the large group can afford taking more risks than the smaller group, by occupying the riskier strata.
Describe paternity confusion
To avoid infanticide, females tend to associate with many males in order to mate with more than one male to confuse the paternity. When males are not sure to be the father, the likelihood to commit infanticide is reduced.
How can females living in the same group use their cycles to avoid infanticide?
How does this work?
by having synchronous cycles
the alpha has less chance to conceive when many females cycle, showing that they mate with other males since the alpha cannot monopolize all the females at the same time
How does post-partum oestrus relate to infanticide
, in primate species showing post-partum oestrus, no infanticide is observed, while infanticide is common in species not having exaggerated sexual swellings.
What is thought to be the origin of pair-bonding
when infanticide risk is high, females will associate with males.
eg in baboons: after the birth of an infant, females spend more time in proximity with males than before. In mirror, after the death of an infant, females do not associate
anymore with males.
Do females associate with males in one-male units ?
yes - females associate with the likely father
chnages in association are usually associated with infant death
Is there male-female association in mountain gorillas
How does this affect group size
yes even though they live in harem societies
females associate with the most likely father
group size is highly variable within a given year due to female migration, either arriving in the group or leaving the group. These changes of group size are due to infanticide by males.
What did Watts find about the relationship between female transfer and infanticide in mountain gorillas (2)
What is this evidence of
female transfer, in most of the cases, occurs simultaneously or subsequently to the infanticide committed on their infant
, in most of cases of female transfer, females join the infanticidal male.
infanticide is indeed a strong pressure for females to associate with
males, either to hang out with the likely father, or to confuse paternity.
What are the predictions associated with within-group contest competition
individual feeding rates and food quality decreases with dominance rank, and that high ranked individuals spend more time resting and socializing, while low-ranked individuals spend more time in feeding and traveling to search for food
Describe the ecology of white faced capuchins
White-faced capuchins are frugivore primates that live in multi-male multi-female groups, where foods are highly patched and so where within-group contest competition is assumed to be strong
What did Vogel 2005 find regarding the validity of the assumptions for within-group contest competition regarding female relationships
high-ranked females aggress more and low-ranked receive more aggression
High-ranked better energy intake
as aggression rates increase, the difference in intake rates between dominants and subordinates increases
In capuchins , feeding rates follow the position in the hierarchy. What is this a direct result of
a direct consequence of the competition for high quality food
The SEM’s assumption for contest competition is high ranked spend more time resting and socializing, low-ranked more time in feeding and traveling to search for food. Is this bourn out in the data?
In vervet monkeys, high ranking individuals, particularly in females, spend less time moving than low-ranking individuals, following the prediction of high within-group contest competition
in olive baboons,, high ranked individuals gain more
energy and better food intake as compared to low-ranked females, but here this difference doesn’t translate in differences in activity budget.
in olive baboons,, high ranked individuals gain more
energy and better food intake as compared to low-ranked females, but here this difference doesn’t translate in differences in activity budget. What may explain this?
low-ranked individuals have to follow the activity pace of the group, given that olive baboons who live in the savannah have a lot of big predators, obliging all individuals to follow the group.
What are the predictions for female relationships in the SEM scramble competition within groups
individual feeding rates decrease with group size, which is confirmed by findings in mountain gorillas.
large groups have larger home-ranges and larger groups have larger daily traveling distances.
Are the predictions of the SEM scramble competition supported by the data
Steenbeck & van Schaik, 2001 found In Hanuman langurs, a folivore species living in India, when home-range sizes as function of group size are plotted, it confirms that larger groups have larger home-ranges
also found Longer traveling distances for larger groups
Meanwhile in mountain gorillas Grueter (2018) this relationship is not linear as daily traveling length is higher for intermediate group sizes
thus inconsistent
(a differential in quality patch may explain this non-linear relationship, more similar to what would happen in case of within-group contest competition.)
What is the folivore paradox
Scramble competition within-group
-> should support large group sizes
BUT relatively small group sizes
give 3 explanations for the folivore paradox
small group sizes may be due to depletion of food patches, limiting group expansion;
female reproductive success may be better at
intermediate group size, due to increased scramble competition.
infanticide risk may limit group size increase, as female disperse to avoid harassment by males, keeping group size below optimum
What are the predictions for contest competition between groups
when food patches are not monopolizable.
Here, home-ranges show a high degree of overlap, and the intensity of between-group competition is mostly affected by population density.
observations seem to confirm this rule
How does within group competition affect group size
Within-group competition increases with group size
What kind of relationships do females get into when food is clumped
Contests for clumped food lead females to make coalitions with kin
Give 4 features of Dispersal-egalitarian:
- Low within and between-group competition
- No dominance relationships, no hierarchies
- No female coalitions
- Dispersal not costly
Which primate species fall into the dispersal egalitarian social system
lemurs,
most folivore species such as gorillas, langurs, howler monkeys, colobus.
There are inconsistencies among folivores in term of predictions and observations, such as alliance formation in some species
Give examples of folivores who don’t quite fit in the dispersal egalitarian social system
chimpanzees and bonobos are assumed to be in this category,
but chimpanzees show a high degree of between-group competition and females form a linear dominance hierarchy,
bonobos have a lower degree of BGC, but also form linear dominance hierarchies among females, and females form coalitions.
What are the 5 features of resident egalitarian social structures
- Low within but high between-group competition
- No dominance relationships, no clear hierarchies
- No long-term alliances
- Coalitions for between-group competition
- philopatry, stay with kin
Which species belong to the resident egalitarian group?
Are there any inconsistencies
patas monkeys, most guenons and mangabeys
eg patas monkeys, most guenons and mangabeys
What are the 5 features of a resident nepotistic social structure
- High within but low between-group competition
- Formal dominance relationships, linear hierarchies, submission signals
- long-term alliances and coalitions with kin
- costly dispersal (lose alliances)
- philopatry
Which primates are part of the resident nepotisitc social structure (4)
Are there any inconsistencies?
macaques,
baboons,
capuchins
vervet monkeys.
macaques show a strong phylogenetic signal in their social relationships, with varying degrees of submission and nepotism, not associated with competitive
regimes,
in capuchins where between-group contest competition can be very strong.
What primates are part of the Resident-nepotistic-tolerant group
What is interesting about this
all Sulawesi macaques fall in this category
Given these macaques showed much higher levels of tolerance than other macaques, it seems that there was a need to provide an extra category for them.
What are the features of resident-nepotistic-tolerant primate social structures (6)
- High within and high between-group competition
- Formal dominance relationships, linear hierarchies,
submission signals - long-term alliances and coalitions with kin
- philopatry
- costly dispersal (lose alliances)
- relatively tolerant dominance relationships, to not
lose support from low-ranking when in BGC
What elements of the SEM have reach a consensus (6)
acting that females are the ecological sex, since female reproductive success is limited by access to resources;
males aggregate around females and so male reproductive success is limited by access to females;
food types, distribution and quality lead to different competitive regimes;
scramble competition
limits group size;
contest competition promotes kin-based alliances,
food, predation and male mating strategies are important selective pressures on female grouping
Give data validating that females are the ecological sex
in chimpanzees, that core area
quality is associated with a better female reproductive success; that better food is reflected in better
reproduction (Emery-Thompson & Wrangham, 2008)
In female vervet monkeys, access to better food in females is associated with dominance and hierarchy, as dominance improves access to resources and thus improve a lifetime reproductive success. (Isbell et al., 1999)
Give data to show males aggregate around females and male RS is limited by females
less chances to conceive when more males are present in a group of wild chimpanzees
male-male competition for mating, resulting in a reproductive skew where chances to sire are reduced for groups with more adult males
Kutsukake & Nunn, 2006
Show that dominance is an adaptive mating strategy in males
alpha males have priority of access and get the highest percentage of copulations as compared to low-ranked males
Stoinski et al., 2009
What are female social relationships ultimately determined by
it is not clear if female social relationships are ultimately determined by ecological conditions, neither if social behaviour is so adaptive or merely just inherited from a past ancestry. Here the role of phylogenetic constraints is important, as shown in macaques
What are the key controversies of the primate social systems
- Are female social relationships determined ultimately by ecological conditions
- How adaptive or inert is social behaviour ?
- female dispersal patterns: cause, consequence or circular effect?
- role of phylogenetic constrainsts
- inconsistencies between models‘ predictions and observations:
Folivore paradox
Prolonged social relationships between sexes outside of breeding period
Aggression rates do not always match predictions (in particular dispersal patterns)
Summarise the controversy surrounding primate female dispersal
depending on the models, as the dispersal-foraging efficiency model presented in the previous lecture, it is not so clear if dispersal is a cause or a consequence of the social organisation and of the competitive regime, or if its embedded in a circular loop so that when ecological conditions change it is impossible to switch from one system to the next.
Give an example of a primate species that perfectly shows the inconsistencies the SEM
in Colobus vellerosus, a species of
folivore colobus, researchers found that females show low levels of grooming, no female coalition
over food and female dispersal. These parameters fit perfectly with a dispersal-egalitarian system.
However, they also found that female-female affiliations were much higher than female-male
affiliation, which goes against what is expected for a dispersal-egalitarian species and corresponds
more to a resident behaviour.
What were the explanations given for the inconsistencies of the SEM in Colobus vellerosus?
affiliation among females can be a response to male harassment and infanticide risks, where coalition formation among females do not act within feeding competition, but against males, as seen in wild bonobos.
IN which systems is sperm competition seen
in multi-male multi-female mating systems, like in chimpanzees
What 3 key things does the fact that male RS is limited by females lead to
It creates a strong male-male competition, which leads to a strong sexual dimorphism, as in one-male mating systems like gorillas.
Male-male competition is also leading to sperm competition, as seen in multi-male multi-female mating systems, like in chimpanzees.
Male-male competition also leads to a reproductive skew, where only few males get most of mating and copulations, while the majority of males never gets access to females, either within a group or within a population.
How does male LHS differ from female LHS in terms of longevity?
Is this always true?
Lower survival in males is most likely due to the fact they take more risks, to defend a group, against enemies or predators, and due to fierce male-male competition, but also due to a more stressful life than females
in species where males are caregivers, males survive longer than females.
Generally, caregivers live longer as they need to live longer to look after their offspring
What is the classic male strategy to access females in multi-male multi-female societies
dominance
High rank increases reproductive success
Give pros and cons of males fighting their wa up the hierarchy
+ it increases reproductive fitness
- exhaustion
- in high ranked individuals, testosterone levels are high (this is detrimental for health, in primates, humans and
other mammals)
How do testosterone levels change with dominance rank
testosterone levels increase with dominance, and thus decrease when individuals go down the hierarchy (e.g., when they get older)
What is tenure
the length of which an individual keeps a high rank
How does tenure length differ with number of females in single male groups
why (2)
Tenure length decreases as the number of females increases in the group due to high takeover and difficulty to monopolize access to females when there are many
How does tenure length differ with number of females in multi-male groups
why (2)
while in these groups males have a longer male tenure, tenure length also decreases with the number of females
How does frequency of female breeding affect male tenure
male breeding tenure is also shorter in species in which females breed frequently than in those where females breed less frequently.
What does stress level depend upon
allostatic load: cumulative physiological burden as individuals adjust their morphology, physiology and behaviour to transitory factors
How do stress levels compare between dominant and subordinate individuals
In cooperative breeders,
dominant individuals are more stressed than subordinates. In other social systems, subordinates are
more stressed than dominants.
What did Ostner (2008) find when comparing stress levels in established adult males and in subadults
What can explain this
In large subadults, stress level increases as their rank increases, while in established adult males, it is the opposite: dominant males are less stressed than subordinates
high ranked individuals buffer stressful events with their relationships and bonding with other males
How can higher ranked males buffer stress
via social relationships or conflict avoidance
How does sociality relate to hierarchy in Asamese macaques
give the study
sociality increases with dominance, where dominant individuals are more social than subordinates
sociality predicts future dominance success
males with strong bonds improve their reproductive success
Schulke et al., 2010
What do subordinate males get out of alliances with more dominant males
Give 2 examples of this
subordinate friend males get mating opportunities
In wild chimpanzees, political support is exchanged with mating -
Duffy (2007) found mating success increases with support given to the alpha male
Feldblum et al., (2021) found Wild subordinate chimpanzees are more likely to sire if they have strong bonds with the alpha male
How does the improve RS of subordinates from forming friendships affect reproductive skew
male reproductive skew is actually not so skewed
In Barbary Macaques, it was found that there is very little reproductive skew as most males end up copulating with females, due to these coalitions
In one-male groups or in multi-male multi-female groups, what are male-male relationships
related to
the level of within-group competition (WGC) and the level of between-group competition (BGC)
What is the WGC and BGC in one male groups and what dictates this
In one-male groups, like most gorilla populations, resident males expulse natal males from the group and prevent any immigration, resulting into a low WGC among males, but a high BGC
What is the WGC and BGC in multi-male groups and what dictates this
males form systems of dominance and hierarchies and males also tend to prevent the arrival of new males. This results into a high WGC but also a high BGC.
When is within-group male-male competition low
w in situations where female choice is stronger than male-male competition, as in polyandrous and monogamous mating systems (also true for humans)
when female reproduction is synchronized,
which results in females not being monopolized.
How does a male primate’s strategy change throughout life
Young males get most of the
mating, tenure can be quite short, and they often have one-sided relationships (asymmetric
relationships where the subordinates give more than they receive). This results in a certain reproductive skew (e.g. in baboons and rhesus macaques, where most of mating are obtained by
young males in their prime)
Old individuals get less mating opportunities but they also change the way they interact with other individuals: they form more friendships with females and have more equal and mutual social relationships with other males.
Compare the strength of older and younger primate males
exemplify this
When it comes to aging, one would think that older males are less strong than younger ones but it is not necessarily the case
in rhesus macaques, the
number of offspring sired, as function of age: most offspring are sired by young males in their prime, but body mass is not changing over time
What is the ability to stay as alpha dependent upon
not necessarily a question of physical strength, but rather related to the capacity to form coalitions with young partners
How do male relationships in chimps change with age - use a specific study
, in wild chimpanzees, of the number of mutual friendships as function of age: mutual friendships increase with age, while the number of one-sided relationships decreases with age.
Rosati et al., 2020
True or false
In most primate species, males stay with their natal group at sexual maturity.
False
In most primate species, males leave their natal group at sexual maturity.
What do newly mature males do once they have left their natal group
Males can either enter a new group at the bottom of the hierarchy, for multi-male groups, or they can try to take over a group of females by excluding the resident male, and killing all the babies, like in one-male mating systems
Do males usually disperse alone
No
Since dispersal is costly and dangerous, because males don’t have the protection against predators that the group offers, it is common to observe male dispersal in cohorts, sometimes brothers, who form bachelor groups
What is the main ultimate explanation for any kind of dispersal whether male or female
to avoid inbreeding within a group
Are there any primate species where both or neither sex disperses?
. There are no primates where both males and females stay in their group.
there are few species where both males and females disperse, as in monogamic species like gibbons.
What is the key factor affecting timing of male dispersal
What does timing of second dispersal depend upon
kinship
the place in the hierarchy attained after arrival, and on other males arriving.
How does kinship affect timing of male dispersal
Gerber (2016) studied long-tailed macaques and found Males who have many family members in the group, the plain line, are more likely to postpone their next departure than males who have less relatives in the group
What did Marty (2016) glean from studying black crested macaques regarding hierarchy and second dispersals
The timing of secondary dispersal here depends on the place in the hierarchy attained after arrival, and on other males arriving.
If a low rank is achieved in a new group, males emigrate again once another male arrives. Here, these males do not reproduce but they suffer of no injury.
If a high rank is achieved in a new group, these males emigrate again, but later, not matter if new males have
arrived. Here, they achieve a high reproductive success but suffer injuries when they get kicked out.
Name 3 patrilocal primate species
What must males do in these societies
chimpanzees,
bonobos
some spider monkeys
In these societies, young males have to climb up the hierarchy rather than dispersing
What is cooperation between males in patrilocal societies facilitated by?
What is supposed to happen in theory
kinship, between brothers and half-brothers
males compete with other groups to get the best habitats that are supposed to attract more females
What is the evidence for males compete with other groups to get the best habitats that are supposed to attract more females in patrilocal primate societies
Poor evidence for this female attraction effect has been found so far, at least in
chimpanzees and bonobos
In bonobos, between-group competition is low and females are codominant. In these patrilocal societies, within-group competition between males takes place over access to females, with the formation of dominance hierarchies, coalitions, mate-guarding and female exert their female choice on the males
Give an example of how primate mating systems can be flexible for pair bonded species
Where has this example been seen before
In pair-bonded species, the rule is that one male stays with one female, protects the infants and is territorial (typical monogamous system). However, if BGC increases, due to increase of population density or reduction of habitat quality, a primary male has to tolerate other males, here cooperatively defending the range against other groups, resulting in a polyandrous system
among siamangs
Give an example of how primate mating systems can be flexible for single male unit species
Where has this example been seen before
. In single male groups, if BGC increases, similar
effect occurs, with a primary male tolerating other males, resulting in a polygynandrous system
lowland western gorillas
Describe polyandry in primates
several males stay with
one female and provide paternal care to the offspring; males tolerate each other and the female will confuse paternity by mating with all the males.
Give an example of cooperation in extreme environments between non-human animals
penguins for thermoregulation
What was Smith (1964) theory for the evolution of cooperation
kin selection
related individuals cooperate with each other
the idea that an altruistic allele can improve its prevalence in the gene pool by promoting the success of the same allele in other individuals
What was Trivers (1971) theory for the evolution of cooperation
Reciprocal altruism
cooperation is maintained by reciprocity of exchanges (individuals cooperate only with those who also cooperate)
What was Wilson (1975) theory for the evolution of cooperation
Group selection
groups of cooperators outcompete groups of noncooperators.
What is the equation for inclusive fitness
Inclusive fitness = RSself + (RSothers * r)
. Inclusive fitness includes the individual own fitness, plus the fitness of its relatives weighted by the degree of relatedness
Describe the theory behind reciprocal altruism
if the costs of cooperation are low and the benefits are high, altruistic alleles can spread by mutually promoting their success. In this situation, individuals reciprocate altruistic acts, and this system enables long-term relationships.
True or false
Kin selection leads to nepotism in primates
Justify your answer with 2 examples
true
In baboons, most of social bonds are formed among family members, even if individuals can form friendships also with non-kin, but the rule is, among females, to associate and hang out with mothers, sisters and daughters
In black-and white colobus, grooming and proximity relationships can be influenced by kinship
Give 2 methods of kin recognition in primates
familiarity
phenotypic matching
For which types of relationships can familiarity be a valid form of kin recognition
mother-offspring
siblings raised by same mother
siblings and half-siblings? depends on mating system
Why does the mating system matter for half siblings using familiarity as kin recognition
When only one male is present, most likely all infants and juveniles are siblings and half-siblings. When multiple males live in the group, it is a bit more complicated to recognize beyond the matriline.
What does phenotypic matching entail and require
using physical similarities between individuals
individuals need to use a referent, such as their mother or themselves (if they can recognize themselves). They would then use visual or olfactive clue.
What is the evidence for phenotypic matching in primates
Some studies show that chimpanzees can do it, other studies show that they can’t, some show that macaques fail while other studies show that they can use phenotypic matching
What are necessary conditions for reciprocal altruism
costs must be low and benefits must be high.
a slow life history, for repeated interactions to happen,
a relative stability of the group, to keep tracks of interactions,
service-dependent behaviour, in the sense that one service can be reciprocated by another service, or by the same service.
Give an example of a service dependent behaviour in bonobos
grooming can be exchanged with food sharing
food sharing probability is higher in bonobos when grooming has been exchanged among partners beforehand
Can grooming only be traded for food sharing in primates
no can also be traded for tolerance
in tufted capuchins, of the tolerance among two individuals in two conditions: when they had no mutual grooming before, and they had groomed before. Individuals are more tolerant with each other after a session of reciprocal grooming
furthermore, more grooming after being tolerant at
food resources
Tiddi et al., 2011
Is there cultural group selection in non-human primates
originally assumed to be no
BUT
in chimpanzees, some recent findings point in the direction of group-level benefits of cooperation. Chimpanzees carry on regular border patrols, mostly by males even if females can also participate, and patrols are typical collective and cooperative action with
movement coordination and a common objective.
In Ngogo, in Uganda, decades of observation on
border patrol participation reveal interesting outcomes. What are these and what is the impact for group selection theory
males who had more to gain because they have many offspring in the group participate more, which corresponds to an individual benefit.
high ranking and physical strong males tend to participate more, also here
suggesting an individual benefit.
males who have no offspring or no relatives in the group also regularly participate, hereby suggesting a group interest or group benefit (though can also be seen as individual benefits, just cumulated);
patrolling effort does not decrease with group size, as would be expected if only self-interested males would participate. This suggests again a group benefit and the absence of defection. T
What is the idea behind the discoveries about chimp border patrols in Ngogo?
male participation is maintained because the benefits issued from patrols, such as territory increase, allow group size to increase, conferring a larger competitive advantage to the group against other groups.
Debated whether or not this corresponds to group selection of just to additive individual selection, given that the mathematics behind group and individual selection is the same.
What are the costs and active and passive benefits of friendships in primates
Risks (costs): aggression
Passive benefits: tolerance near resources
Active benefits: exchange of commodities
What are social relationships structured around in primates
Social relationships are structured around both risks of aggression and benefits of cooperation, and the balance between both is modulated by kinship, friendship and reciprocity
What is grooming important for
forming friendships
removing parasites
reducing stress
What direction does grooming usually work in
often bottom-up, following the hierarchy,
with subordinates giving more than receiving
In what way can grooming be used as a market commondity
What is an advantage of this
by being exchanged against other favours such as tolerance, support during conflicts, protection and mating.
Grooming is an easy behaviour to reciprocate, by mutual grooming.
How are grooming patterns affected by kinship
eg in rhesus
macaques, a very nepotistic species related individuals receive more grooming
than non-related ones
Call et al., 1996
How do partner choice and population density affect grooming patterns
the top 3 non-kin partners receive more grooming than top 3 kin partners, especially in high density. So here friendship matters more than kinship, especially at high density where tension between individuals is increased (given these are captive populations).
Friends do not keep
track of every single interaction. The long history between individuals, the fact they live together for
a long time, outweighs the single interactions. Therefore, how can primates keep track of cooperation?
What is the proximate mechanism
emotional score-keeping: nice interactions are remembered, and reciprocated
oxytocin plays a major role in this emotional score-keeping and in promoting socialbonds
Give evidence of the role of oxytocin in emotional score-keeping (2)
urinary oxytocin shows higher levels in bonded grooming partners, whether
they are kin or not, than in non-bonded grooming partners
oxytocin is higher among bonded partners than among non-bonded partners, and even higher than among kin partners in males.
Crockford et al., 2013
Do chimps form long friendships?
yes
In chimpanzees, males form stable long-lasting and reciprocal bonds
How does friendship affect fitness in chimps
Wild subordinate chimpanzees are more likely to sire if they have strong bonds with the alpha male
Feldblum et al., 2021
What are the 2 types of food sharing in wild chimps
Why is food sharing important
passive form, which is more or less a form of food tolerance,
and
active food sharing, which is rare among animals and primates.
Food sharing is assumed to reinforce social bonds
Do adoptions occur in the animal world
Adoptions happen in mammals, but these are rare events.
In the Taï chimpanzees, where female mortality is high, due to predation and diseases, it is common to have young chimpanzees becoming orphans and being adopted by group members who look after them.
Is adoption in chimps cooperative in an evolutionary sense?
Evidence your answer
Yes
Boesch et al., 2010
In Taï chimpanzees, 18 adoptions have been observed across 3 communities during 27 years of research. Half of the adoptions were made by an adult male, and only one was made by the biological father. In this population, the presence of kin in the group does not influence the probability of adoption
Thus, adoption can be seen as a form of altruism, even if group benefits such as keeping a high number of individuals cannot be excluded. Individuals adopting provide substantial help to adoptees, such as food sharing and carrying them on their back
What are the 7 key periods of life history
Gestation Birth Growth Reproduction Maturation Senescence Death
Why are Darwinian demons not possible
resources and energy are limited. These limitations due to resources get translated throughout evolution by evolutionary constraints, where natural selection cannot maximize fitness beyond certain limits
What is a life history trade-off
when an increase in one life history trait (improving fitness) is coupled to a decrease in another life history trait (reducing fitness), so that the fitness benefit through increasing trait 1 is balanced against a fitness cost through decreasing trait 2.
Define LHS
Life history strategies are inherited patterns of energy allocation to these basic functions at different
points during the lifespan
What are the 3 main posts of energy expenditure in LHT
reproduction, maintenance and growth
Compare growth vs maintence in LHT
Maintenance mobilizes energy for repair of the body, vigilance, feeding, sleeping and the immune function.
Growth mobilizes energy for the development of muscles, organs and the brain.
Are LH strategies static
no they evolve and are dynamic
they can changed based on:
-extrinsic mortality changes (more or less predation, new diseases, …)
-changes in food availability, distribution and abundance
-changes in mate availability
-changes in alloparent availability
Give an example of a LH trait that is deeply phylogenetically constrained
Hyraxes.
Hyraxes are small mammals that live in Arica, measuring between 20 and 70 cm and weighing not more than 5kg. Given their size, one would expect a relative short gestation period.
However, hyraxes have a relative long gestation period of about 8 months.
This trait, related to reproduction, is inherited from their ancestry. Ancestors of hyraxes were large mammals and hyraxes are the closest living relatives to elephants, who show a long gestation period predicted by their body mass.
Give typical features of a fast LHS
fast growth, high
reproduction output, short lifespan, rapid ageing and small size, are favoured in environments with
high mortality risk,
while this can evolve under natural selection, but physiology can also respond to cues during the life course through plasticity.
Which mammal order adopted the slowest LHS
primates
Primates have a longer lifespan as compared to other mammals (on an allometric scale, where primates are above the rest of the mammals for relative body weight).
Primates have also small litter sizes (shown in
another allometric scale, below other mammals relative to body weight).
Charnov & Berrigan, 1993
What is the average interbirth interval in primates
what is the longest in primates
2.3 years, with a maximum of 8 years in orang-utans
Give the key features of a general primate LHS
- Late maturation→ long juvenile period → long maternal investment
- Slow reproduction
- Single offspring (max. 2 Callitrichids)
- Low adult mortality, long reproductive career
- Long life span
- Females live longer than males
What does maternal investment usually involve
where the mother nurses and provides milk during the first months of life,
carries the infant, interacts with her infant, by playing and grooming, and she protects her offspring
against other group members, against bad climatic conditions and against predators
What is direct and indirect paternal care in primates
direct, by carrying
the twins, by grooming them and sharing food with them;
indirect, in the form of protection and tolerance.
Name a primate species known to have paternal and maternal care of offspring
Callitrichids
Who can be an alloparent
Allo-parental care can be provided by other males (who could potentially be the fathers) as in multi-male groups were paternity is uncertain; by young females, by related individuals like older daughters, and in cases of adoption by a group member, related or not.
What makes primate maternal investment so costly
What does this costliness lead to
a long period of gestation, a relatively long period of lactation, and substantially
some forms of food sharing
trade offs between current and future offspring
How do trade offs between current and future offspring manifest in wild chimps
Does this effect persist across offspring lifetime
offspring being bigger when the inter-birth interval is longer, meaning that delaying the next reproduction benefits the current offspring.
The effect of a differential parental investment is persisting over the
adolescence period, where bigger offspring remain bigger and smaller ones remain smaller as they
grow.
The effect of a differential parental investment is persisting over the adolescence period, where bigger offspring remain bigger and smaller ones remain smaller as they grow. Give evidence for this
. Shown by the relationship between creatinine, a marker of muscular mass, and age, between
offspring that were looked after by their mother more than 5.5 years and those that were looked after for a shorter period of time those that were looked after for a short period of time remain smaller
What is the Triver-Willard hypothesis
Parental investment should be optimally allocated toward the sex that has the highest anticipated reproductive success
(1973)
According to the Trivers-Willard Hypothesis (1973), What is the optimal sex of offspring for a high- and low-ranking female to have
How should this differential be expressed
→ high-ranking females should favour sons
→ low-ranking females should favour daughters
This differential should then be expressed and should appear in the sex-ratio at birth and in a differential investment after birth depending on the mother’s rank and on the sex of the offspring.
Give the reasoning behind the Triver-Willard hypothesis
Given that male RS can be quite high, though variable, due to the winner-loser effect inherent of being a male as a primate, and given that females will always have some RS, the theory says that high-ranking females should invest into sons, and that low-ranking females should invest into daughters.
Is there much support for the Trivers-Willard hypothesis (1973)
Boesch, 1997, found in wild chimps dominant females invest more into sons - IBIs are longer for dominant females who have a son, reflecting a longer investment in this current offspring, and inter-birth interval of subordinates is longer when they have a daughter as compared to subordinate mothers who have a son.
In addition, when looking at survival curves of sons and daughters of dominant and subordinate mothers, we can see a clear effect of this longer investment in sons from dominant mothers, as their sons enjoy a better survival. In contrast, sons from subordinate mothers, who tend to resume reproduction fast, have the lowest survival probability
less conclusive regarding sex ratio - Brown and Silk 2002: Meta-analysis 35 studies:
No clear evidence for differential birth sex-ratio
Summarise the findings of Boasch (1997)
in wild chimps:
dominant females invest more into sons
Longer IBI for dominant with a son
Subordinate IBI longer if they have a daughter
Sons of dominant
mothers survive better
(Trivers-Willard Hypothesis (1973))
Is there any evidence for change in sex ratio according to Trivers-Willard Hypothesis 1973
Perret, 2018, investigated the paternal effect on maternal physiology.
In mouse lemurs, t high testosterone levels in dominant males were correlated with more produced male-biased litters, suggesting a paternal effect rather than a maternal one.
However, overall, differentiated investment at birth, resulting in differing birth sex-ratios, receives little support across primates
What is a key issue (other than sex ratio) with the Trivers Willard Hypothesis (1973)
investment may be linked to philopatry rather than direct fitness depending on the sex
Why is philopatry a problem for the Trivers Willard Hypothesis (1973) (3)
Male chimpanzees are philopatric, so it seems to pay to invest into sons when high-ranking, because sons will then have more chance to reach a high status in their own group.
Also, in female philopatric species, it would pay to invest into daughters when highranked, due to the rank inheritance that daughters benefit off.
Also, in female philopatric species, it would pay to invest into sons when low-ranked, since males may then gain a higher potential RS, especially because their mother’s rank is not passed to these males.
Give a typical example of parent-offspring conflict seen in mammals
weaning
Describe weaning as a parent-offspring conflict
For the mother, it pays to wean her infant earlier so that she can invest into the next reproduction. From the infant perspective, it pays to keep suckling to get more free energy without having to invest into solitary foraging.
Conflict occurs after the the more is ready to wean but before the offspring is ready to wean
How can you observe parent-offspring conflict
For example, mother-offspring conflict
can be seen by looking at the number of contacts between them: during this period of conflict, the
mother breaks the contacts with her infant more often than the infant does, while the infant
constantly searches for more contacts.
What is a juvenile
Weaned individuals (not infants, stopped suckling)
Travel and feed independently
Pre-pubertal (not yet reproductive)
What are the sex differences that can be observed in the primate infant-juvenile transition (5)
Males physically grow faster than females
males play socially earlier than females do
female social development, in particular grooming, gets developed faster than for
males
Males tend to play more toward objects while females tend more to play a type of play called play-parenting
juvenile capuchins tend to follow the foraging habits of the same-sex adults, females overlapping in foraging habits with their mothers, while juvenile males will overlap with what adult males feed on.
In apes, where tool use has been extensively studied, some sex-differences occur
What is the sex difference in physical growth in the primate infant- juvenile transition due to
How can we see this change
due to differences in the development of the motor control
can be witnessed by looking at the first time they travel independently
Give an example of motor control developing differently in different sexes in apes
Give an example for other primates
In wild chimpanzees, independent traveling increases over time
for both males, in black, and females but independent traveling increases faster in males than in females. (Lonsdorf, 2014)
in blue monkeys, males decrease faster the contacts with the
mother than females do
Give examples with apes and other primates of how social play differs between the sexes in the infant - juvenile transition
in chimpanzees, young males increase their rates of social play during infancy faster and earlier than do females. (Lonsdorf, 2014)
in Japanese macaques, social play increases with age in both sexes but males tend to display more social paly than females. (Eaton et al., 1986)
Give examples of how grooming development differs in primate juveniles
in Japanese macaques, of the percentage of observation time where females and males were seen engaging into social grooming, as function of their age: already during the infancy females groom more than do males, mostly toward their mother
This difference persists over time, during the juvenile period, with juvenile females who groom more often their mothers than do little sons.
Eaton et al., 1985
How does play orientation differ between juvenile primates
Give examples
What is the purpose of this thought to be
Males tend to play more toward objects, as seen in
wild chimpanzees, while females tend more to play a type of play called play-parenting
in chimpanzees, some juvenile females have been observed playing with a stick and carrying the stick as they would carry an infant. In many other primates, play of young females directed toward other infants, such as interacting, carrying and playing with a baby have been observed, like in Western lowland gorillas, rhesus macaques, bonnet macaques and blue monkeys.
These sexdifferences in play-orientation are thought to be predispositions for mating competition and
parental investment, strategies that differ between males and females.
Give examples of how there are sex differences in juvenile primates in who they acquire foraging skills from
In chimpanzee termite fishing, females are more attentive to their mother’s techniques than males are, which results in a shorter acquisition time, and so in a greater proficiency for females than for males
Lonsdorf (2005) found the time spent fishing termites is much higher and grows faster over age in females than in males, and that the percentage of time spent watching the mother fishing termites is much higher in females than in males, especially at a young age.
HOWEVER, in chimps:
In other types of tool use, however, such as ant dipping, no sex difference appears.
in nut cracking behaviour, not sex difference has been observed throughout the ontogeny of this behaviour,
Why does the acquisition of nutcracking and antdipping skills not show a sex difference?
in ant dipping, no sex difference appears, probably because eating on ants is a risky foraging technique (due the bites of ants) that needs time to acquire.
nut cracking: probably because getting skilled in nut cracking takes a lot of time, erasing potential difference that may exist in term of attentiveness or interest in learning the technique.
What are the risks of a juvenile period?
Why have this period
juvenile growth is slow, and juveniles can’t reproduce
3 hypotheses:
ecological risk aversion hypothesis
brain energy hypothesis
needing to learn hypothesis
Describe the ecological risk aversion hypothesis
individuals stay small for a while to buffer high morality risks, high mortality risk due to high predation on small bodies and least efficiency in feeding. So, since juveniles are poor feeders, it would not pay to have them growing to full size too fast, they need time to acquire good skills to forage efficiently
Describe the brain energy hypothesis to explain why primates have a juvenile period
large brains need a lot of energy, so the cost of brain development constrains energy available for body growth. In other words, large brains slow down development. Here again we have this idea of trade-off: the energy needed for brain development cannot be allocated to body mass.
Describe the needing to learn hypothesis to explain why primates have a juvenile period
it takes and needs time to develop full socio-ecological skills, such as foraging skills but also social skills like learning the hierarchy and other social attributes
Why do primates live so long?
Slow development and delayed reproduction have to be compensated by longer reproductive lifespan
→ What keeps adult mortality low?
Only viable if adult mortality is low (otherwise risk of dying before reproduction)
Why is primate mortality low (2)
large brains
arboreal primates and arboreal mammals live longer
Why do we think large brains lead primates to live longer
primates that have larger brains live longer
large brains allow reducing risk of mortality, being more clever help to survive
large brains allow a better diet, better predation avoidance, and enable cooperative skills
Allman et al., 1993
How strong is the relationship between lifespan and brain size in primates
very strong
can be seen across all primate species or across diet, with leaf eaters and fruit eaters; and across social systems
Summarise the trade-off between large brain, slow life history and fitness outcomes
a slower life history pace allows directly the possibility to develop large brains. These large brains in turn incur some fitness costs, such as adjusting to a slow development and a slow reproduction, but it guarantees fitness benefits, such as higher adult survival, traits that in turn comforts and maintains a slow life history.
Why does arboreality increase primate longevity
easily escape to large predators, which are mostly terrestrial.
individuals living in trees are less exposed to diseases
Give evidence of arboreality increasing longevity
Shattuck & Williams, 2010 constructed an allometric scale of lifespan as function of body mass, for all mammals - the line of arboreal is above the line
of terrestrial, showing a higher lifespan for those who live in trees.
Give 6 consequences of a slow LHS
Greater dependence on flexible learned behaviour
Long parent-offspring association
Larger social groups
Association of females with males
→ Stable groups, long-term relationships, cooperation
→ Overlapping generations: social learning, culture
What is a benefit of long parent-offspring association in primates
social learning opportunities and ability to have the time to develop a large brain
How does a slow LHS allow larger social groups
individuals can form long-lasting relationships and need each other to learn and survive
What is the permanent association of females and males in primates with slow LHS due to
mostly due to sexual
coercion by males who, due to the fact they have time, can be coercive with females and push them
to stay with them permanently
