Linking genes, environment and behaviour Flashcards
Adaptive function of behaviour
Behaviour can evolve and change
Sometimes behavioural change allows individuals to survive
Konrad Lorenz (1965) suggests that adaptive change in behaviour occurs through the action of two processes: ontogeny and phylogeny
Behaviour is altered in ways that reflect environmetal change
certain body/physical structures can pre-adapt a species for other behaviours
Phylogeny
Governed by principles of evolution by natural selection
Phylogenetic change takes place across generations within a species
Mechanism for change operates at level of individual:
Individual carries the gene
Genes are only passed on if the individual reproduces successfully
Phylogenetic change depends on ontogenetic change
Ontogeny
Development/change in behaviour within an individual’s lifetime due to changes in environment or:
Maturation - pre-natal development of structures, growth, and age-dependent postnatal changes
Learning- relatively age dependent changes in behaviour as a result of experience and is crucial to survival because rapid changes in behaviour (or behavioural strategies) in response to environmental change, means you may be more likely to survive.
Male orangutans
Reproductively mature by 10 years (younger in captivity)
May not become physically mature (with cheek flanges and enormous body sizes) until many years later depending on social status
Orangutan species
Bornean orangutans: 57,000
Sumatran orangutans: 13,000
Tapanuli orangutans: 800
Arrested adolescence
Sexually mature males who do not fully develop physically
Only one fully physically mature male lives in a particular area but arrested males can still impregnate females
If a mature male dies, an arrested male develops within a year and becomes the dominate male
Arrested adolescence is much more frequent in Sumatra than in Borneo
2 species of Pan
Chimpanzee (Pan troglodytes)
* live in rainforests & savannah
woodlands of west, central & east
Africa
* 100 years ago: >1 million across Africa
* Now: < 300,000
Bonobo (Pan paniscus)
* Restricted to south of the Congo River
(Democratic Republic of Congo)
* Now: ≈ 10 000 bonobos left
Four subspecies of Chimpanzee
- Western Chimpanzee (Pan troglodytes verus)
- Nigeria-Cameroon Chimpanzee (Pan troglodytes ellioti)
- Central Chimpanzee (Pan troglodytes troglodytes)
- Eastern Chimpanzee (Pan troglodytes schweinfurthii)
- (possibly small southern subspecies, P.t. marungensis)
PSYCHOLOGICAL WELLBEING IN CHIMPANZEES
- Work-life balance (opposite to us- too much leisure
not enough work? Obesity issues?) - Choice & control (perceived rather than actual?)
- Personality (mid-life ‘slump’ or crisis?; personality
‘clashes’ with others- breeding partners,
companions)
Activity budget for chimpanzees
Activity budget (daytime) for
wild adult females:
* 30% foraging
* 40% resting
* 30% travelling
Activity budgets (daytime) for
captive chimpanzees have:
* less ‘work’ (foraging &
travelling) &
* more ‘leisure’ (resting)
Possible problems in captivity:
boredom, ‘aberrant’
behaviours, stereotypy, obesity
CHIMPANZEE SOCIAL STRUCTURE
(Gombe, Tanzania)
LIVE IN LARGE COMMUNITIES (unit-groups):
- usually 40-60 chimpanzees (can be 15-120)
- sex ratio approximately equal
COMMUNITY HOME RANGES about 50 km2 - but 600 km2 in dry miombo woodland in Ugalla
district, Tanzania
BROADLY TERRITORIAL - ranges may overlap by 20%, but always > 5 km
between two groups
Chimpanzees travelling
Usually TRAVEL IN SMALL GROUPS:
- up to 10 in Gombe, up to 20 in rainforest
- Fission: Fusion society
Bisexual groups (males & estrous females): - travel about 4.5 km/day
- adult males especially have preferred travelling
associates
Nursery groups (females & young) travel only 3 km/day
Individuals (especially males) indulge in elaborate
greetings, such as embracing, after reuniting
CHIMPANZEE DIETS
DIET MAINLY FRUIT (ESPECIALLY FIGS)
* Eat 100+ plant species
- spend 6-8 HOURS A DAY feeding
– feeding peaks 7–9 a.m. & 5 p.m. - termites eaten at the beginning of
rainy season - Nut-cracking at some sites (hammer
& anvil) - also eat meat
– hunt Red Colobus & other
monkeys
– occasionally bushbuck, young
bushpig
Chimpanzee NESTING
NESTS USUALLY IN TREES
(ground nests at Bwindi & Bili):
* 10-12 metres up
- Usually lower than
orangutans, higher than
gorillas - Not usually roofed over
- Nests are in groups of 2-6
DAY-NESTS are often made for
mid-day siesta, especially in rains
Chimpanzee GROOMING
USUALLY RECIPROCAL- especially after greeting
- Up to 10 in a grooming chain
- Adult males groomed more than
females - Estrus females groomed more than
anestrous females - Individuals (especially adult males)
have preferred grooming partners - 50% of all grooming is male-male;
21% is male-female (49% at Gombe) - Little female-female grooming
Chimpanzee REPRODUCTION at MAHALE, TANZANIA
Age of first swelling:
* 10.7 years (10.8 at Gombe)
Adolescent sterility:
- 2.9 years (2.4 years at
Gombe)
First birth: - 13.2 years (12-23 years)
- 13.3 years at Gombe
- 13 years at Bossou
Female fecundity (fertility)
highest at 20-35 years of age - annual birthrate 0.2
Average female (n=26) has:
* 3.9 infants but only 1.4 of
them survive to be weaned
Older females (18-48 years) more successful:
- gave birth to 2.7 infants
- and 2.0 infants weaned
Chimpanzee reproduction cycles
At least 2 years after birth before female begins to cycle again:
* 24.5 months at Taï
* 46.3 months at Gombe
* 53.2 months at Mahale
INTERBIRTH INTERVAL:
* 72 months (6 years)after son
* 66 months (5.5 years) after
daughter
* 66 months (5.5 years) at
Gombe
* 69.5 months at Taï
* 86.4 months (7.2 years) at
Kibale
CYCLE LENGTH:
* Av. 35 days in mature
females
* Av. 50 days in adolescent
females
* Cycling often very irregular
* sometimes brought on by
large bisexual aggregations
* Evidence of synchrony in
cycles between regularly
associating females
Chimpanzee mating strategies
Maximum sexual swelling lasts:
6-10 days (87% of copulations then)4 MATING STRATEGIES:
(1) PROMISCUITY
* estrous female mates with
many males successively
* very conspicuous & previously
thought to be typical mating
(2) POSSESSIVENESS
* dominant males may prevent
other males mating with estrus
females
(3) CONSORTSHIP (ON ‘SAFARI’)
* most chimpanzees show partner preference
* 1 male & 1 female travel together over 1 or more of
female’s estrus periods:
▪ tend to move away from centre of community
range, towards boundaries
▪ very quiet & inconspicuous, to avoid detection by
dominant males of own community & members of
neighbouring community
▪ Mahale 8% of matings; in Gombe 28%; in Taï 31%
(4) EXTRA-COMMUNITY MATING
* at Taï , one juvenile (out of 34) fathered by male from
another community (DNA evidence)
* at Gombe, 13% observed to be extra-community
Female chimpanzee dispersal from home community
When females reach adolescence they tend to leave their home community
At MAHALE: females disperse at 11 years (9.7-14.0)
& 13% transfer again
At GOMBE: 13-50% disperse & none transfer again
At TAÏ: 95% disperse & none transfer again
Chimpanzee life expectancy
Up to 9 years, young still with
mother 50-60% of time
* Then drops to 15-20%
Life expectancy at birth:
* 11.9 years (at Gombe)
* 19.9 (at Kibale)
* 16.4 years (at Taï)
Life expectancy at age 15:
* 12.9 years (at Gombe)
* 15.4 years (at Kibale)
* 8.9 years (at Taï)
Chimpanzee male dominance
May be a single ALPHA MALE, but he can be displaced by a coalition
* Male rank depends on acquiescence & assistance of high-ranking females
* At Mahale, alpha male had 46% of copulations & 73% of those with newly arrived females
* Alpha male is offered meat by the possessor of a carcass
ALPHA MALE MAKES MOST DISPLAYS:
* rain-dance/ waterfall display
* 3-4 minutes of vigorous rhythmic
branch-waving & dragging during a rainstorm
* buttress drumming
Chimpanzee GANG ‘WARFARE’ BETWEEN COMMUNITIES
HOSTILITY BETWEEN NEIGHBOURING COMMUNITIES:
* Lone individuals of neighbouring community may be attacked & killed
* Active patrolling of boundaries
In Gombe, southern community (Kahama) gradually
split from the main northern one (Kasakela) after 1968
– it had 6 males, northern one had 11 males
* By 1972, their ranges still overlapped by 50%
* By 1973, almost no overlap
* In 1974-5, the northern males made 3 attacks on the
southern, resulting in final extermination of southern
community
Chimpanzee hunting at Gombe
- 55% of prey is red colobus (monkey)
- 35% is non-primate
- Of ≈ 500 red colobus in Gombe
chimpanzees’ range, 75-175 killed by chimpanzees every year - Annual mortality rate in colobus
population due to chimpanzee
predation is 15-35 % - Between 1990 and 1995, one
chimpanzee (FRODO) accounted for ≈ 10% of red colobus in the home range of the Gombe chimpanzees - Red colobus often successfully mob chimpanzees
Chimpanzee hunting at TAΪ (IVORY COAST)
Colobus detected (by ear) in the distance:
* only 31% of hunts are opportunistic; in over half,
there are obvious signs of hunting intention
Chimpanzees fall silent:
* walk swiftly, close together, one behind the other,
stop regularly, are alert
* may silently change direction
Searches last 5-50 minutes (av. 16½)
Hunters cooperate and adopt roles:
* some wait in ambush, in trees or on ground
* one or two chase the Colobus
Chimpanzee TOOL-USE & TOOL-MAKING
(AT GOMBE & MAHALE)
- grass stems & twigs are
modified to probe
termite mounds - long leafy branches are
used to sweep up ants
from nests - clusters of leaves are
used as sponges to
obtain water from tree holes & to wipe sticky substances from the hair
Chimpanzee TOOL-USE & TOOL-MAKING (AT TAÏ & BOSSOU)
Sticks up to 13 cm long are used
to:
* probe for wood-boring bees,
insects under the bark of fallen
trees, driver ants & honey
* inspect each other’s wounds
* investigate dead animals
Logs or stones are used to crack:
* two species of large, hard-shelled nuts (Panda & Coula)
* placing other logs or stones
underneath as anvils
Bonobo Pan paniscus
- Bonobo
- Pygmy or gracile
chimpanzee - Restricted to south of
Congo River - The second species of
chimpanzee, genetically
close to other species of
chimpanzee (Pan
troglodytes) - very different in behaviour!
DIFFERENCES BETWEEN
BONOBOS & CHIMPANZEES
BONOBOS:
* Squat when resting
* Calls are more shrill, almost birdlike
* Temperament is livelier & ‘nervous’, their
movements quicker
* Red lips
* MUCH LESS AGGRESSIVE
* Female genitalia never quite detumesce &
copulate throughout the sexual cycle (for
pleasure)
* show female homosexual behaviour (G-G rubbing)
ANATOMICALLY, BODY
PROPORTIONS MORE LIKE
HUMANS:
* smaller, rounder heads
(skulls)
* longer rear legs
* stand more upright (often)
* difference in weight
between males & females
more humanoid, females
average 85% of male
weight (in chimps they
average <75%)
WILD BONOBOS: ACTIVITY BUDGET
Feeding ≈ 40%; Resting ≈ 32%; Travel ≈ 16% &
Interacting with others (mainly grooming) ≈ 6%
DAILY RANGE mean 2 km
Bonobo social structure (at WAMBA)
- Communitiy sizes at
Wamba in 1980s, about
70-120 - Home range size 58 km2
- Home ranges of different
communities overlap very
widely
Bonobo female dispersal
FEMALES DISPERSE: sometimes
changing groups again after short
periods
* Overall sex ratio 1:1
* more adolescent females than
males,
* probably because dispersing
females only enter new
communities for short periods
All males seem to stay in their natal
community
Bonobo FISSION-FUSION SOCIETY
PARTY SIZE AVERAGES 16.9 (usually 6 - 35)
* At Lukuru mean 6.4 (1-22);
* At Lomako mean 4.9 (1-16)
Membership of a party usually stable for 2-3 weeks or longer
(unlike chimpanzees)
96% OF PARTIES CONTAIN ALL AGES & SEXES
* unlike chimpanzees
* At Lomako, bisexual parties were only about 70%
Proportion of oestrous females in a party can be as high as
98%
Occasional all-male parties (last only 1-2 days)
Bonobo USE OF HABITAT TYPES (at WAMBA)
At Lukuru (southerly site, with dry forest & grassland):
* primary forest: 38%
* secondary forest: 56.2%
* grassland: 4.1%
* riparian forest: 1.7%
* they wade waste-deep into water to gather algae
& sub-aquatic vegetation
Bonobo diet at Wamba
Mostly Fruit (pulp & seeds), shoots,
leaves, flowers, bark, stems, pith, roots, mushrooms, small
mammals, grubs, earthworms,
honey, eggs, soil
* At Lomako: eat snakes, adult
insects & blue duikers
* At Lukuru: eat a lot of THV
(terrestrial herbaceous
vegetation)
Earthworms are a favourite but
form a tiny proportion of diet:
– bonobos dig for them with
their hands
Bonobo nesting
NIGHT NESTS mainly in bokumbo tree (Leonardoxa)
* About 13m above ground (38% at 10 -15m)
* At Yalosidi, 7% of nests on ground
Less selectivity for DAY NESTS
* About 20m above ground (5 - 25m common)
CONSTRUCTION TIME:
* night nests 222 seconds or nearly 4 mins (96-412 secs)
* day nests 42 seconds or < 1 min (3-241 secs)
Bonobos mating
Male typically solicits: 73% of cases
Female presents either:
* dorsoventrally: female stands
quadrupedally facing away
from male
* ventro-ventrally: female lies on
back in front of male
Copulation most frequent (70%)
early morning, between 5.30-9 a.m.
* frequent at feeding sites
* female may exchange food for
sex
Genito-genital (GG) rubbing:
* 2 females clasp v-v, rubbing clitoris
tips together
* Occurs during periods of heightened
excitement
* Creates ‘harmonious stability’
Juvenile males sexually precocious
* join in during copulation, thrusting at
adults’ genitalia
* mount adult & adolescent females
* Adult males may thrust at them
Juvenile females hardly ever engage even
in GG rubbing
Aggression in bonobos
Many males have:
– torn ears, missing finger joints, scars
– aggression much less frequent than in chimpanzees
* Glaring, bluff charging, charging, chasing & leaping
while waving arms over another’s head
* Biting, hitting, kicking, slapping, grabbing, dragging,
brushing aside, pinning down, shoving aside
SUBMISSIVE GESTURES INCLUDE:
– prostration, grimacing, flight, avoidance, extending the hands,
touching the other’s body, shrieking
* Most frequent at feeding sites
* Charging display similar to chimpanzees & often involving
branch-dragging
* Often subdued by dominant male mounting the subordinate, but
no intromission observed
MALE BONOBOS FAR LESS AGGRESSIVE THAN MALE CHIMPANZEES
Bonobo WITHIN & BETWEEN-GROUP RELATIONS
At feeding sites:
* females often take precedence over all except highest-ranking males
Group of females may form a coalition against a male:
* males don’t form coalitions to attack a female
Close associations between females at Lomako are 6-7 x
as common as those between males
Neighbouring communities may avoid one another, or
there may be mild aggression but:
* NO COMMUNAL WARFARE has been observed
Why the difference between Bonobos and Chimpanzees
IN BONOBOS, FEMALE CHOICE IS CRUCIAL IN MATING
* groups more cohesive than chimpanzee groups,
e.g. party size often 25-30% of total community
size, but usually <20% in chimpanzees
- Social use of sexual behaviours increases females’
social status, & so reduces the reproductive value
of copulation (Furuichi & Hashimoto, 2002)
PARTY SIZE & COHESIVENESS MAY RELATE TO:
* constant presence of ‘superabundant food
patches’ (White & Wrangham, 1988)
* or overlap in community ranges, & need for
protection (Hohmann & Fruth, 2002)
Gorilla species
Eastern gorillas:
Mountain gorillas - 1000
Grauer gorillas - 3800
Western gorillas:
Western lowland gorillas - 125000 and only subspecies found in zoos
Cross river gorillas - 300 and
Activity budget of wild western gorillas
50-70% feeding
10% travelling
15-35% resting
Gorilla Developmental milestones for females
Menarche: 7-7.5 years
First birth: ≈ 10-11 years in wild
Life expectancy: at sexual maturity can live on
average another 17-19 years
Gorilla Developmental milestones for males
Mating: ≈ 15 years (wild), 6-10 years (captivity)
Becomes silverback: at 12-13 years
Life expectancy: after becoming a silverback, lives
on average another 10 years
Gorilla NATURAL HABITATS: ALTITUDE & FOREST TYPES
Most gorilla populations live:
altitude: from sea level - 1000 m
forest types: lowland rainforest & swamp forest, especially
secondary forest; bais (waterlogged
clearings in rainforest); avoid
monodominant areas (single plant species)
In mountains west of Central African Lakes, Grauer’s
gorillas live:
altitude: up to 2500 m
forest types: montane rainforest (including bamboo)
Mountain gorillas live:
altitude: at 3000 - 3500 m in Virunga Volcanoes
forest types: montane forest (including bamboo), Hagenia
forest, giant heath & Afro-alpine zones
Gorilla diet
Basic dietary staple is Terrestrial
Herbaceous Vegetation (THV)
Virungas: THV only: leaves, herbs, stems,
pith, roots, bulbs, lichen, bark
Intermediate mountain zones: more fruit
eaten (10-20% in Kahuzi & Bwindi)
Lowland forest: much fruit eaten (40-
63% in West African regions)
– Gorillas prefer fruit & range widely
in search of it
– in Sangha valley region, gorillas
enter bais & forage for aquatic
vegetation, which has high mineral
content (Na, Ca, K)
Gorilla SEASONAL VARIATION IN DAILY RANGES
EASTERN GORILLAS: no seasonal difference
WESTERN GORILLAS:
* fruiting seasons: groups travel far in search of fruit
* non-fruiting seasons: groups restrict their ranges &
feed on THV
– Lopé, Gabon (mixed forest): in fruiting seasons ≈
1266m; in non-fruiting seasons ≈ 749m
– Bai Hokou, CAR: reduces from 3100m to 2110m
– Mondika, CAR (swamp forest): reduces from 1648m
to 1118m
Gorilla nests
On the ground typical in
many places
Percentage of tree nests is
higher in Grauer’s gorillas
than in other gorillas
In a multi-male troop: each
silverback & his mates nest
close together
Gorilla group composition
VIRUNGAS: 1970s & 80s, most groups 1
silverback; 1990s, 28-40% had >1 silverback
– females usually disperse, often several
times
– rank order reflects order in which they
became dominant silverback’s mate
– a few all-male groups recorded
KAHUZI BIEGA: 8% of groups are multi-male
(silverbacks)
WEST AFRICA: most groups have 1 silverback
– Maya Maya 0%; Mbeli Bai 8%
– No all-male groups recorded
Gorilla relations between groups
Silverbacks of 2 groups (or solitary male & group male):
* Auditory display- communicate by hoot-series followed by
chest-beats
If groups are close, chest-beats are replaced by:
* Auditory & visual display- ground-thump or branch-breaking or
* Visual display only- vegetation tearing & sideways run
GORILLAS USING TOOLS
Chimpanzees & orangutans use natural objects
as tools in wild, & sometimes modify them
(i.e. make tools).
IN 2005: 2 different adult female gorillas were
observed to use tools use at Mbeli Bai, Congo
(Breuer, Ndoundou-Hockemba & Fishlock,
2005).
Efi & Fulani (her infant): stand at the edge of a
clearing. Efi detaches a stem with both hands,
pushes it into the ground, and uses it to
stabilize herself while she pulls aquatic plants
towards her with her other hand
LIFE CYCLE OF GORILLA GROUP
(Virungas only)
Male reaching maturity (becoming a silverback):
chooses to stay or emigrate
If he stays (64%): he mates with unrelated females
who join the group or are already in it (in Virunga,
potential mates include half-sisters)
If he emigrates (36%): he becomes solitary &
begins to follow groups seeking females
Female reaching maturity:
usually (72%) emigrate & join another group
that has approached
All adult males (solitary & group males) try to gain females from
other groups:
* usually invade another group & ‘persuade’ females to transfer
– younger males display at invader
– dominant male tries to keep females & young in background
– a very bloody fight between silverbacks may occur
– there may be infanticide
Solitary silverback who gains 1 female:
will try to gain others
if he cannot attract other females, the first soon leaves him
Strong silverback keeps all his females:
& may eventually lead a group of over 30 gorillas
Gorilla INFANTICIDE
In Virunga, infanticide accounts for at least 37% of infant mortality:
- occurs most frequently after death of silverback in a one male unit, but also during inter-group encounters
- Infants in one male units more likely to die from infanticide than those in groups with multiple silverbacks
- not recorded, even in equivalent circumstances, in Western or Grauer’s gorillas
Gorilla mating
- Females solicit males unless another male is trying to
compete - Have been observed mating ‘face-to-face’
- Females develop small, white labial swelling for 2-3 days
around ovulation & mating is restricted to this time - During pregnancy, all females mate:
– generally with other males (not prevented by mate)
– or mount other females
Gorilla REPRODUCTIVE PARAMETERS
Gestation: 257 days
Cycle length:
– 32-33 days (Western & Grauer’s
gorillas)
– 28 days (Mountain gorillas)
Age at weaning: 3-4 years
Inter-birth interval:
– 47-51 months (if infant survived)
– 12-26 months (if infant died)
POPULATION DENSITIES
(where chimpanzees & gorillas sympatric)
- gorillas more ‘patchy’
distribution - chimpanzees more even
distribution - gorillas build up much
higher population
densities
Bonobos human behaviour
Bonobos yawn when they see a stranger yawn and exhibit altruistic behaviour. They also laugh.
Dark side of behaviour in apes
Adult arrested males rape females
Gorillas mostly peaceful but some males commit infanticide when they replace a rival male
Male chimpanzees bash females to assert dominance
Bonobo are ranked in pairs (male and female equally) much less violent. Sex is used to resolve conflict and community encounters are peaceful and relaxed.
