1.7: Primate socio-ecology

Question 1

Socio-ecological model

Answer 1

The environment influences a species’ social system

Question 2

How does the environment shape social systems? (2)

Answer 2

Want for food

Defence against predators

Question 3

How does the environment shape female behaviour?

Answer 3

Female reproduction is limited by resources (food, safety)
If food is scarce: females live alone to avoid competition
If high-quality food is clumped/low-quality food is evenly spread: females form groups to defend food cooperatively and reduce predation risk

Question 4

How does the environment shape male behaviour?

Answer 4

Male reproduction is limited by access to females

Males map themselves onto the distribution of females

Question 5

How does monogamy result? Give an example.

Answer 5

Females live in solitary
Males cannot monopolise more than one of them
E.g. Gibbons

Question 6

Polygynandry

Answer 6

Multi-male-multi-female societies

Question 7

How does polygynandry result? Give an example

Answer 7

Females live in groups
Strong males may monopolise multiple females partly, but cannot monopolise them all
E.g. Baboons

Question 8

Polygyny

Answer 8

One-male-multi-female groups

Question 9

How does polygyny result? Give an example.

Answer 9

Female fertility is desynchronised
‘Harems’ and ‘bachelor bands’ develop
E.g. Gorillas

Question 10

Polyandry

Answer 10

One-female-multi-male societies

Question 11

How does polyandry result? Give an example.

Answer 11

Females give birth to multiple offspring
Males may be willing to reduce offspring mortality to increase their own reproductive success
E.g. Tamarins regularly have twins but don’t have the temporary sterility associated with nursing in between children, so they will have twins and already be pregnant with the next twins; females have multiple fathers for one litter

Question 12

Orang-utan distribution

Answer 12

Sumatra
Borneo
(Indonesia, Malaysia)

Question 13

Orang-utan habitat

Answer 13

Lowland rainforest
Mangrove
Rarely above 1000m

Question 14

Oran-utan appearance

Answer 14

Coarse red hair
Bright orange in immatures
Chestnut ref in adults
Cheek flanges in adult males
No female ano-genital swelling
Quadru-manual clamberer

Question 15

Orang-utan life style

Answer 15

95% arboreal
Night nests are built every day
Sometimes dwell in day nests

Question 16

Orang-utan diet

Answer 16

60% fruit
40% other plant parts
Occasionally bird eggs
Insects (termites, ants)
Young squirrels

Question 17

What does an orang-utan social unit consist of?

Answer 17

Solitary adult males
Adult females with dependent offspring
Solitary adolescents

Question 18

What are the two models of orang-utan social life?

Answer 18

Fully grown male controls a large area that encompasses several smaller female home ranges

Larger communities made up of adult males and females with their maturing sons

Question 19

Orang-utan characteristic traits

Answer 19

Heaviest arboreal animal
Slowest reproductive rate
Least sociable ape

Question 20

Orang-utan mating strategy

Answer 20

Male cheek flanges and throat-sacks amplify loud calls at male competitors
Females resist copulation attempts of non-flanged males (rape)
Non-flanged males are intentionally at a subadult stage as an alternative mating strategy

Question 21

Gorilla distribution

Answer 21

West, Central, and East Africa

Question 22

Gorilla habitat

Answer 22

Lowland and montane forest
Meadows
Swamp
Flooded forest
Savanna

Question 23

Gorilla appearance

Answer 23

Knuckle walker
Massive body
Black fur
Often low hair density
No female ano-genital swellings

Question 24

Gorilla diet

Answer 24

40% fruit in Western, 1% fruit in Mountain
34% leaves (herbs) in Western, 68-86% leaves (herbs) in Mountain
21-27% stem, pith, shorts
<0.1% bark, wood, flowers, roots, tubers, invertebrates
Anecdotal evidence of bird eggs and cannibalism

Question 25

Gorilla social life

Answer 25

Tendency to form harems with 11 members: 1 silverback, 5 immatures, 5 females
40% of groups have 2-4 silverbacks (adult males + matured sons)
Smaller harems/bi-male groups develop where gorillas eat more fruit, which increases competition
Harem holders change through violent ousting/death
Sons tend to inherit father’s harem
Females pick a harem of their choice and transfer between them several times
Little social contact amongst unrelated females

Question 26

Gorilla characteristic traits

Answer 26

Males display to competitors through bipedal locomotion and chest beating
New harem resident may kill offspring sired by predecessor (infanticide)

Question 27

Chimpanzee distribution

Answer 27

West, Central, and East Africa

Question 28

Chimpanzee habitat

Answer 28

Evergreen and semi-deciduous rainforests
Open woodland-savannah
Gallery forests
Mosaic habitats that may include plantations and grassland

Question 29

Chimpanzee appearance

Answer 29

Knuckle walker
Black or pale face
Thin fur
Sometimes long fur

Question 30

Chimpanzee lifestyle

Answer 30

Active in the day
Some activity during the night, particularly during full moon
50% terrestrial (males spend 40% daytime in trees, females spend 60% daytime in trees)
Each night they build a new nest/sleeping platform in trees from leafy twigs

Question 31

Chimpanzee diet

Answer 31

56%-71% ripe fruit
18-21% leaves
Other plant-parts
Terrestrial herbs
11-23% faunivory constitutes
Cooperatively hunt 25 vertebrate species (80% colobus monkeys, 20% other mammals)
Occasional cannibalism

Question 32

Chimpanzee social life

Answer 32

Live in communities of between 20-100 members (av. 41)
Communities range over 5-38km2 in forests and 25-560km2 in open habitats
Communities forage in small groups of 6, different members can join or split from these groups
Males are philopatric
Females leave their natal community upon sexual maturity
Males are more closely related than females
Males cooperate to defend their range against neighbouring communities with whom they engage in lethal conflicts (lethal raiding)
Patriarchal

Question 33

Chimpanzee characteristic traits (10)

Answer 33

Tool manufacture and use
Use tools to extract resources and in social contacts
Communal hunting
Males do most of the hunting and females do most of the gathering
Food sharing
Aggressive intergroup encounters (proto-warfare)
Infanticide from own and neighbouring groups
Promiscuous mating system
Males use displays and coalitions (chimpanzee politics) to establish themselves as alpha-males
Behaviour diversity between different populations due to local traditions in technologies and social arenas (cultures)

Question 34

Bonobo distribution

Answer 34

Democratic Republic of Congo

South of the Congo River

Question 35

Bonobo habitat

Answer 35

Primary lowland rainforest

Question 36

Bonobo appearance

Answer 36

Paedomorphic (juvenile) chimpanzees
Gracile with slender limbs, head, and shoulders
Reddish lips
Middle parting in hair on head
Black-faced babies
Knuckle-walkers
Bipedal
Female ano-genital swellings

Question 37

Bonobo life styles

Answer 37

Construction of day and night-nests

Most arboreal ape: >50% daytime in trees

Question 38

Bonobo diet

Answer 38

72% fruit
25% leaves
2% herbaceous and terrestrial vegetation
0.1% animal matter

Question 39

Bonobo social life

Answer 39

Fusion-fission communities: 10-58 members, av. 30
Travelling parties for foraging
Female-female relationships govern social life
Females are unrelated
Matriarchal society

Question 40

Bonobo characteristic traits (7)

Answer 40

Complex sexual behaviour (heterosexual: ventro-ventral mating, male-infant contracts; homosexual: female genito-genital rubbing of clitoris (gg-rubbing), male penis fencing; autosexual (masturbation))

Elaborate female-female relationships

Female coalitions dominate males

Hunting is rare, but females hunt and control the meant

Very limited/no evidence of tool making and use

Very limited/no evidence of intergroup aggression

Very limited/no evidence of infanticide