霊長類行動学8. Scramble versus contest competition
Competition
- competition - key is contestability
- seems to be driven by greed, but really driven by limitation of resources
- contest competition: fight for access to resource
- e.g., １０人に一つのパイをあげる際、一箇所に固まっておく→取り合いして勝ったものが取りたいだけ得る。
- scramble competition: rush to gain access to a share
- e.g., divide into a piece and scatter -> 早い者勝ちで取り合う。
- 動物園では餌を散らしてやることで、decrease aggression
- each condition is associated with resources (food / females)
- clumped like fruit -> contest competition
- scattered like leaves -> scramble competition
Competition in Females
manifest as within group or between group
- Availability of fruit depends on its abundance and party size in the teritorry
- females actively defend territory from other groups
Female Orangutan (Fruitgivore)
- scrabmle competition
- females are dispersed in environment
Female Chimp
- classic scramble competition
- group size is big
- usually
- eat fruit
- rainy season
- keep eating fruits, keeping scramble competition, by dispersing more.
Female Gorilla
- scramble competition
- group size is constant
- usually
- eat fruit
- Rainy season
- start eating leaves
- not compete over resources
Female Gibbons
Female Galagos
- strict territory
- classic contest competition even though they eat insects
- in some species, the style of comtetition changes correlating with the group size.
- in some species, they swith contest and scramble competition when the population gets too big in the territory
Competition in Males
- more complected
- female are the resources for male
- contest style changes depending on
- female clumped
- female dispersed
- most male engages in contest competition,
Male Brachyteles arachnoides (めちゃくちゃなやつら)
- scramble competition - another exception
- sperm compeition (sexual selection)
- polygynyandry
Male Chimp
Male Gorilla
- if limited dispersed resource (feamale)
- strong contest competition
- acquisition of territory is scramble competition
- once one decides his territory, he will be fine.
