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
