Socioecology

Week 6: tuesday lecture

Socioecology

study how ecological forces shape the size and structure of social groups

Parameters of diversity

1. # of females/males

2. dispersal patters (philopatry)

3. mating stucture

4. rank relationships

Sociality may be rooted deep in the primate lineage

• earliest primates were probably nocturnal

• nocturnal primates forage alone to avoid predators

• not strictly solitary

Benefits of sociality

1. reduce risk of predation (selfish herd effect)

2. enhances access to food

3. enhances care of young

4. enhances access to potential mates

cost of sociality

1. Competition

2. Contagion

3. Cuckoldry

4. Inbreeding

5. Cannibalism

6. Infanticide

Ecology Pressures Females vs Males

• Females nutritional status = food

• Males access to females = reproduction

Distribution of Food: Clumped

• Valuable patches

• Big enough to feed several monkeys same time

Distribution of food: Dispersed

• Low value patches

• Patches big enough for only 1

Grass Corms

• clumped

• valuable

Water hole

• clumped 

• valuable

Glass Blades

• Dispersed

• Low-quality

• Seasonal

Flowers

• Dispersed

• High Value

• Highly seasonal

Wild Celery

• Superabundant

• Low value

Animal Prey

• Dispersed

• Valuable source of nutrients

Scramble competiton

dispersed, low value resources

• Food is distributed evenly

• Single item not worth fighting over

• Scramble to get enough food, no direct competition

contest competition

clumped, valuable, monopolizable resources

• resources are scare & valuable

• resources are worth fighting over

• contest access to particular resources

Competition: within vs between groups

• groups can compete WITH other groups access to valuable resources

• animals WITHIN groups can compete over access to resources

Strong WITHIN group competition animals

• savanna

• baboons

• rhesus macaques

• white-faced capuchins

asymmetries in resources holding power

• conflict of interest (COI) arises between 2 individuals

• COI generates competition and aggression 

• Age, strength, experience of individuals varies

• Resource holding power = aggregate measure of indi ability to win contests over resources

When rank is linked to resources

• high ranking animals have priority of access to resources

• animals will strive for high rank

• animals may solicit allies to support them in contests

• help is useful bc there is power in numbers

When alliances play important role in females lives

• cultivate relationships with allies

• form alliance with kin

• remain near kin (philopatric)

Competition WITHIN and WITH groups are HIGH

• success of coalition depends of its size

• individuals benefit if group acts as cooperative unit

• low ranking indi won’t participate if they don’t share the benefits

• this favors more tolerant, les despotic relationships among females

Resources are NOT worth competing

• domince rank will not influence access to resources

• females will not strive for high rank

• females will not benefit from alliances

There will be little selective pressure favoring

• female-female bonds

• female philopatry

• female alliances

• matrilineal dominance hierarchies

scramble completion animals

• howlers

• patas

• gorillas

• langurs

BETWEEN group competition HIGH

• females will need allies in between group competition

• females will not disperse

• females will have egalitarian dominance relationship

BETWEEN group competition is LOW

• females have little need for allies in between group competition

• females will disperse

• females will have weakly defined dominance relationships

Males in this picture

• females philopatric = males must disperse to prevent inbreeding

• females disperse = males may remain in natal group or disperse

What influences the number of males in groups

• predation

• # of females