霊長類行動学16. グループ形成の理由

observational and deductive science
status of Primatology was how much they had data
people were interested in
- 1. descriptive study:
  - details of behavior
- 2. correlational study
  - ecological correlations of grouping patterns
findings were based on correlational study

provided intensive discussion
- 1. "primate form groups because of predation risk"
- 2. "sexual selection is very important"
brought those discussion

changed the way of study in Primatology
introduced a hypothetical deductive framework
- 1st principle is
  - 1. prediction
  - 2. test
looked at relationship between behavior and ecology
Wrangham did
- 1. changes the way we classify social systems of primates
  - groups are not fixed entities
  - instead, they are a product of underlying patterns of male and female behavior
    - response to environment
- 2. emphasized importance of understanding the explanatory model
  - now, primate became data to test hypothesis
- 3. focuses on female as a driving force behind
  - group organization
  - thought to be that males solely play the key roles.
  - his arguments were too biased, but the idea opened up the question

two different kinds of groups of females
- 1. Kin
- 2. non-kin
Wrangham classified primates based on the type of group not based on group size
- 1. "female bonded" - female stays in natal group
  - forms affiliative bonds with other females
- 2. "not female bonded" - female leaves natal group
establish the criteria to distinguish "female bonded" from "not female bonded"
- 1. do female breed in natal group?
- 2. do female transfer out of natal group?
- 3. do female engage in affiliative actions
  - e.g., grooming, haddling, dominate, assistance, etc
now, we can test hypothesis like if "Japanese macaque is female bonded"

cooperation must be an Evolutionary Stable Strategy (ESS)
- he was creating a model, the mechanism
rules:
- suppose there is a fruit tree that can support only two individual
- There exists a linear dominance hierarchy: A>B>C>D
Condition 1: within dyadic competition (two fight with no support from others)
- A, B on the tree, C, D on the ground
Condition 2: any two individuals can cooperate, and they can defeat any other.
- (how to form the cooperation tends to be based on kin.)
- C+D on the tree, A, B on the ground, but soon
- A+B on the tree, C+D on the ground
Thus, grouping is needed for intergroup feeding competition.
He argues that
=> grouping patterns based on environmental condition
- if one exploit patchy, high quality resources
  - females bond
- if one exploit disperse, low quality resources
  - no bonding
=> male attaches for resource defense
- sexual selection is secondary for the reason to group
- female behavior drives male dispersal
but his discussion about males were mostly wrong.

	female-bonded	non female-bonded
importance of food patches in inter-group interactions	high	low
frequency of female participation in inter-group interactions	high	low
role of female in group more merit	active	passive
frequency of female-female grooming	high	low
~~frequency of male and male grooming in multi-male group~~	~~low~~	~~high~~

Primatology is no longer a correlational study focusing on resource exploitation and resource availability
emphasis on the predictable model.
but where he failed was
- he did not explain the primary question "why" primate form group, but only answerd "how".
- idea about too much emphasis on sexual selection
- he predicted that idea of predation drive grouping will be failed
but inspired people to go out to test, and built the foundation of science in this field.

falsifies food resource competition idea to explain the reason for grouping
very strong hypothetical deductive framework
- existence of alternative model
  - have to test the opponent idea as well
- Wrangham's model had worked well only in folivore paradox

1. to avopid predation
- increasing chance of defense
- too costly for predator to attack
- increase vigilance
2. predation defense + advantages of group living
- help in locating and defending resources
- regulate resource use
3. resource defense
- predation is not an issue
- regulation of group size

1. food is in large patches - if a lot of food
2. individuals can only exploit limited amount of food
- 1. ability to consume
- 2. food itself is toxic (e.g., plant secondary compound), inadequate nutrition
3. different age and sex classes
- use different food items
  - niche separation, niche dimorphism
  - e.g., orangutan, males and females eat different food

1) animals regulate return time to patches
- territory size increase, group size increase, defensibility decrease
- => doesn't work
2) information exchange (like bees)
- benefit from sharing information of food
- food is dispersed in space and time
- they will benefit

he made prediction and rejected all other ideas, but did not do for his model and predation model.

1. predation model' predict group size goes up
- then, fall off as group split
2. intergroup feeding competition (IGFC)
- group size should grow continuously
- high population density -> more competition

1. Predation:
- fecundity falls within increasing group
  - higher competition -> low number of infants
2. IGFC
- feeding increase with group size, then falls off as group get bigger