Linking genes, environment and behaviour

Question 1

Adaptive function of behaviour

Answer 1

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

Question 2

Phylogeny

Answer 2

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

Question 3

Ontogeny

Answer 3

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.

Question 4

Male orangutans

Answer 4

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

Question 5

Orangutan species

Answer 5

Bornean orangutans: 57,000

Sumatran orangutans: 13,000

Tapanuli orangutans: 800

Question 6

Arrested adolescence

Answer 6

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

Question 7

2 species of Pan

Answer 7

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

Question 8

Four subspecies of Chimpanzee

Answer 8

• 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)

Question 9

PSYCHOLOGICAL WELLBEING IN CHIMPANZEES

Answer 9

• 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)

Question 10

Activity budget for chimpanzees

Answer 10

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

Question 11

CHIMPANZEE SOCIAL STRUCTURE
(Gombe, Tanzania)

Answer 11

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

Question 12

Chimpanzees travelling

Answer 12

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

Question 13

CHIMPANZEE DIETS

Answer 13

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

Question 14

Chimpanzee NESTING

Answer 14

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

Question 15

Chimpanzee GROOMING

Answer 15

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

Question 16

Chimpanzee REPRODUCTION at MAHALE, TANZANIA

Answer 16

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

Question 17

Chimpanzee reproduction cycles

Answer 17

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

Question 18

Chimpanzee mating strategies

Answer 18

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

Question 19

Female chimpanzee dispersal from home community

Answer 19

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

Question 20

Chimpanzee life expectancy

Answer 20

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)

Question 21

Chimpanzee male dominance

Answer 21

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

Question 22

Chimpanzee GANG ‘WARFARE’ BETWEEN COMMUNITIES

Answer 22

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

Question 23

Chimpanzee hunting at Gombe

Answer 23

• 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

Question 24

Chimpanzee hunting at TAΪ (IVORY COAST)

Answer 24

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

Question 25

Chimpanzee TOOL-USE & TOOL-MAKING
(AT GOMBE & MAHALE)

Answer 25

• 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

Question 26

Chimpanzee TOOL-USE & TOOL-MAKING (AT TAÏ & BOSSOU)

Answer 26

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

Question 27

Bonobo Pan paniscus

Answer 27

• 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!

Question 28

DIFFERENCES BETWEEN
BONOBOS & CHIMPANZEES

Answer 28

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%)

Question 29

WILD BONOBOS: ACTIVITY BUDGET

Answer 29

Feeding ≈ 40%; Resting ≈ 32%; Travel ≈ 16% &
Interacting with others (mainly grooming) ≈ 6%
DAILY RANGE mean 2 km

Question 30

Bonobo social structure (at WAMBA)

Answer 30

• Communitiy sizes at
  Wamba in 1980s, about
  70-120
• Home range size 58 km2
• Home ranges of different
  communities overlap very
  widely

Question 31

Bonobo female dispersal

Answer 31

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

Question 32

Bonobo FISSION-FUSION SOCIETY

Answer 32

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)

Question 33

Bonobo USE OF HABITAT TYPES (at WAMBA)

Answer 33

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

Question 34

Bonobo diet at Wamba

Answer 34

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

Question 35

Bonobo nesting

Answer 35

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)

Question 36

Bonobos mating

Answer 36

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

Question 37

Aggression in bonobos

Answer 37

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

Question 38

Bonobo WITHIN & BETWEEN-GROUP RELATIONS

Answer 38

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

Question 39

Why the difference between Bonobos and Chimpanzees

Answer 39

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)

Question 40

Gorilla species

Answer 40

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

Question 41

Activity budget of wild western gorillas

Answer 41

50-70% feeding
10% travelling
15-35% resting

Question 42

Gorilla Developmental milestones for females

Answer 42

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

Question 43

Gorilla Developmental milestones for males

Answer 43

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

Question 44

Gorilla NATURAL HABITATS: ALTITUDE & FOREST TYPES

Answer 44

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

Question 45

Gorilla diet

Answer 45

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)

Question 46

Gorilla SEASONAL VARIATION IN DAILY RANGES

Answer 46

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

Question 47

Gorilla nests

Answer 47

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

Question 48

Gorilla group composition

Answer 48

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

Question 49

Gorilla relations between groups

Answer 49

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

Question 50

GORILLAS USING TOOLS

Answer 50

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

Question 51

LIFE CYCLE OF GORILLA GROUP
(Virungas only)

Answer 51

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

Question 52

Gorilla INFANTICIDE

Answer 52

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

Question 53

Gorilla mating

Answer 53

• 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

Question 54

Gorilla REPRODUCTIVE PARAMETERS

Answer 54

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)

Question 55

POPULATION DENSITIES
(where chimpanzees & gorillas sympatric)

Answer 55

• gorillas more ‘patchy’
  distribution
• chimpanzees more even
  distribution
• gorillas build up much
  higher population
  densities

Question 56

Bonobos human behaviour

Answer 56

Bonobos yawn when they see a stranger yawn and exhibit altruistic behaviour. They also laugh.

Question 57

Dark side of behaviour in apes

Answer 57

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.