Primates Pt.2

Answer 1

Anatomical traits and
behaviour linked
– e.g. male-male competition &
sexual dimorphism in body size
and canine size

Answer 2

Behaviour is a product of
natural selection on ancestral
populations resulting in
increased adaptation to
particular habitat

Question 3

Socioecology

Answer 3

Socioecology: the approach
that explains variation in the
social systems of animals with
reference to ecological and
biological factors

Question 4

Availability and distribution of
resources affects what

Answer 4

Availability and distribution of
resources → – competition – grouping – social behaviour – mating patterns

Answer 5

Social behaviour is a suite of
adaptations to the ecological
and social environment

Question 6

what is needed for For survival and fitness?

Answer 6

– Find food
– Find and co-ordinate with mate
– Have offspring & rear offspring
– Avoid parasites & diseases
– Avoid predators

Question 7

Costs of group living
(sociality)

Answer 7

– increased competition for
resources (food, mates)
– increased likelihood of
disease and parasite
transmission
– increased conspicuousness
(predation)

Question 8

Benefits of group living
(sociality

Answer 8

– defense of territory/food
resources & mates from
competitors
– lower risk of predation

Question 9

Benefits of sociality: Lower risk of predation

Answer 9

• Detection
• more eyes to detect predators
• Deterrence
• more individuals to mob or chase
  predators away
• Dilution
• smaller chance that any one individual
  is the prey of the day when group is
  larger-

Question 10

Optimal group size

Answer 10

• The size and
  composition of groups
  reflects a compromise
  between the costs and
  benefits of sociality
  for individuals
  – magnitude of these
  costs and benefits is
  influenced by social
  and ecological factors

Question 11

Males vs. females (4)

Answer 11

Females compete over food

Males compete over females

Question 12

Reproductive success limited by:

Answer 12

Females:
Access to resources
Males:
Access to females

Ecological pressures influence the distribution of females, and
males distribute themselves to maximize their access to females
High metabolic costs associated with
gestation and lactation

Question 13

Food

Answer 13

• Supplies energy
  requirements for survival,
  growth & reproduction
• Dietary specializations
  drive numerous
  specializations
  – body size
  – teeth form and number
  – gut length
  – hand (shape, function)
  – locomotor and suspensory
  systems
  – brain size
• Different kinds of foods in
  different kinds of habitats
  are distributed differently
  in space and time

Question 14

Diet correlated with body size in primates

Answer 14

Insectivores are
smaller than
frugivores &
frugivores are smaller
than folivores
Differences in size are
related to differences
in energy
requirements

Question 15

Adaptations in the digestive tract

Answer 15

Primates unable to
digest cellulose →
microorganism for
cellulose digestion
Colobines: complex
multi-chambered
stomach with
cellulose-digesting
bacteria

Question 16

Diet and brain size
‘Ecological intelligence hypothesis’

Answer 16

• Frugivorous primates
  relatively larger brains than
  folivorous
• → Frugivorous primates
  need larger brains to
  remember location and
  phenological status of fruit
  trees

Question 17

Distributions of resources and defensibility: Clumped distribution

Answer 17

→ May be defended
→ Territoriality

Question 18

Distributions of resources and defensibility: Even distribution

Answer 18

→ Difficult to defend
→ Home ranges without defence

Question 19

Resource competition: Cost of forming (large) groups

Answer 19

Negative effects on
energy
budgets
development
reproductive
performance

Question 20

Resources determine type of competition * Scramble (‘first come first serve’)

Answer 20

Food is evenly distributed
 Amount of food available per
individual decreases with
increasing group size

Question 21

Resources determine type of competition Contest

Answer 21

• Food is found in defensible
  clumps
  – Individuals compete
  aggressively over access to
  resources

Question 22

Dispersal in primates: Baboon-macaque-guenon group* Male dispersal is the norm

Answer 22

• Male dispersal is the norm

Question 23

Dispersal in primates: Colobines, lemurs, apes, New World monkeys

Answer 23

• Female dispersal and
  bisexual dispersal common

Question 24

Why do animals disperse?

Answer 24

• Avoid inbreeding
  – reason in many cases for
  natal dispersal
• Seeking better resources
• Result of intrasexual
  competition
  – but does not explain
  species where individuals
  leave voluntarily

Question 25

Solitary

Answer 25

Males defend home ranges that encompass home ranges of several females

Question 26

Monogamous Pairs

Answer 26

When females are dispersed, males may associate permanently with one of them

Question 27

Polyandry

Answer 27

Several males associate with one reproductive female

Question 28

Polygyny: One-male (‘harems’)

Answer 28

If females are clumped in groups, one male may be able to monopolize access to a group

Question 29

Male infanticide in Primates

Answer 29

* Infanticide by males is major source of infant mortality in primates – especially in single-male groups * Most cases of infanticide follow changes in male residence (eg. takeovers) or dominance rank

Question 30

Polygyny: Multimale (mating system: Polygynandry/promiscuity)

Answer 30

Females clumped in groups, and multiple males associate with them

Question 31

Human mating system

Answer 31

* Majority of human societies allow polygyny * but its frequency depends on subsistence style: – monogamy predominates in forager societies – pastoralists and agriculturalists show significant polygyny

Question 32

Anatomical evidence: Sexual dimorphism (SD)

Answer 32

* Correlation between sexual size dimorphism and polygyny in many mammalian groups * Pronounced body size dimorphism is suggestive of high levels of male–male competition

Question 33

Testis size & mating system

Answer 33

* Primate species in promiscuous mating systems have much larger testes relative to body size than primates in single-male groups (monogamous + polygynous) * Humans: mild level of promiscuity