1.7: Primate socio-ecology Flashcards
Socio-ecological model
The environment influences a species’ social system
How does the environment shape social systems? (2)
Want for food
Defence against predators
How does the environment shape female behaviour?
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
How does the environment shape male behaviour?
Male reproduction is limited by access to females
Males map themselves onto the distribution of females
How does monogamy result? Give an example.
Females live in solitary
Males cannot monopolise more than one of them
E.g. Gibbons
Polygynandry
Multi-male-multi-female societies
How does polygynandry result? Give an example
Females live in groups
Strong males may monopolise multiple females partly, but cannot monopolise them all
E.g. Baboons
Polygyny
One-male-multi-female groups
How does polygyny result? Give an example.
Female fertility is desynchronised
‘Harems’ and ‘bachelor bands’ develop
E.g. Gorillas
Polyandry
One-female-multi-male societies
How does polyandry result? Give an example.
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
Orang-utan distribution
Sumatra
Borneo
(Indonesia, Malaysia)
Orang-utan habitat
Lowland rainforest
Mangrove
Rarely above 1000m
Oran-utan appearance
Coarse red hair Bright orange in immatures Chestnut ref in adults Cheek flanges in adult males No female ano-genital swelling Quadru-manual clamberer
Orang-utan life style
95% arboreal
Night nests are built every day
Sometimes dwell in day nests
Orang-utan diet
60% fruit 40% other plant parts Occasionally bird eggs Insects (termites, ants) Young squirrels
What does an orang-utan social unit consist of?
Solitary adult males
Adult females with dependent offspring
Solitary adolescents
What are the two models of orang-utan social life?
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
Orang-utan characteristic traits
Heaviest arboreal animal
Slowest reproductive rate
Least sociable ape
Orang-utan mating strategy
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
Gorilla distribution
West, Central, and East Africa
Gorilla habitat
Lowland and montane forest Meadows Swamp Flooded forest Savanna
Gorilla appearance
Knuckle walker Massive body Black fur Often low hair density No female ano-genital swellings
Gorilla diet
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
Gorilla social life
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
Gorilla characteristic traits
Males display to competitors through bipedal locomotion and chest beating
New harem resident may kill offspring sired by predecessor (infanticide)
Chimpanzee distribution
West, Central, and East Africa
Chimpanzee habitat
Evergreen and semi-deciduous rainforests
Open woodland-savannah
Gallery forests
Mosaic habitats that may include plantations and grassland
Chimpanzee appearance
Knuckle walker
Black or pale face
Thin fur
Sometimes long fur
Chimpanzee lifestyle
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
Chimpanzee diet
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
Chimpanzee social life
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
Chimpanzee characteristic traits (10)
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)
Bonobo distribution
Democratic Republic of Congo
South of the Congo River
Bonobo habitat
Primary lowland rainforest
Bonobo appearance
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
Bonobo life styles
Construction of day and night-nests
Most arboreal ape: >50% daytime in trees
Bonobo diet
72% fruit
25% leaves
2% herbaceous and terrestrial vegetation
0.1% animal matter
Bonobo social life
Fusion-fission communities: 10-58 members, av. 30
Travelling parties for foraging
Female-female relationships govern social life
Females are unrelated
Matriarchal society
Bonobo characteristic traits (7)
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
