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2011-09-21

霊長類行動学3. 霊長類社会構造(Social Structure)

霊長類行動学もくじ

Social Systems:

  • the network of behaviors and patterns that emerges from the conflux of mating and rearing patterns, grouping patterns/ demography, and intragroup and intergroup behavior.

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gregarious (with others): e.g., oysterssolitary
social (interact with others)asocial: e.g., tiger
  • all primates are social
  • most primates are gregarious
  • nocturnal animals tend to be solitary
  • orangutansolitary but social
    • 基本的にはひとりで生活するが、仲間に出会うとハグをしたりして交流する。

  • Demographic
  • mating system or breeding system
    • include grouping pattern / association pattern
    • people tend to think it is not but in fact, it is a selfish act in nature (no mutual agreement in nature)

Grouping
  • a primate group: based on collection of individuals that engage in regular, patterned social contact over extended periods of time and use the same general spatial areas.
    • change over time
    • but most species do exhibit one or more basic general demographic patterns in their social groups

  • grouping types (Demographic labels) of Extant primates
    1. Multimale / multifemale
      • The group consists of more than one adult female and more than one adult male and immatures
        1. Variants: cohesive group, the majority of individuals within the group occupy the same general areas at the same time, generally within vocal and/or visual range for the majority of active time
        2. fission-fussion: the overall group breaks into smaller subgroups of variable composition but ses similar range; subgroups can fuse into larger groups, or the entire group can occasionally occupy the same area at the same time; fissioning or fusion may be seasonally and/or behaviorally diriven
        3. Community: similar to fission-fusion; however, subgroups are more dispersed and less likely coalesce into full group
    2. Unimale / multifemale
      • a cohesive group consisting of one adult male and more than one adult female and young
    3. Unifemale/multimale
      • a cohesive group consisting of one adult female and more than one adult male and young
    4. Two-adult group
      • a cohesive group consisting of aone adult female, one adult male, and immatures.
    5. Dispersed society
      • individual primates with individual ranges that overlap extensively; interactions between individuals within the overlapping ranges can be frequent or infreqent. vocal and / or visual and / or tactile; occasionally multi-individual subgroups may form.

  • Solitary
    • forage or sleep alone
      • sometimes group together for sleeping
      • usually definition of solitary includes when mother/offspring together
    • nocturnal animals tend to be solitary
  • group (gregarious)

Territorial

  1. live in territory
    • territorialは一定の場にとどまろうとする特性、それを守ろうとするかは種次第
  2. defend territory like chimp
    • 2 reasons (to guarantee the following 2 resource abundance)
      1. food
      2. mating

breeding system (mating patterns)

1. monogamy

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  • 1 mate during reproductive cycle
  • male and female are monogamous (お互いにとって相手はひとりのみ)
  • not necessarily being socially bonded, but rather in terms of sexual behavior.
  • very rare in mammals because males is Monogamy if and only if they were forced to be.
    • Humans are only primate of which group doesn't have specific territory
  • two types of monogamy
    1. serial monogamy (一生同じ相手だとは限らない。)
      • characteristics of humans (Homo)
    2. life time monogamy
    3. pair bonding:
      • one type of monogamy
      • attached each other (not only the reproductive way, but also for the life)
      • e.g., tity monkey

2. polygamy
  • more than one partner
2.1 polyandry(poly- many, andras- man / 一妻多夫制)

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  • single female and more than 1 male.
  • male provides parental care
    • males carrying children around
  • dominant female kills other females
  • extremely rare, more than monogamy
  • e.g., Saguinus
2.2 polygyny(poly - many, gyny - "female" /一夫多妻制)

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  • single male and multi-females
  • small group size (2~3 females)
  • resident male gets "tenure" in terms of reproduction
  • age-granded

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    • 若いオスは、silver-bucksが死ぬのを待つか、自ら去る
    • e.g., Gorilla

2.3 polygynandry
2.4 promiscuity

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  • multi-male / multi-female
  • no structural patterns.
  • mating with everybody
  • メスがそれぞれの場所に待機してるところに、オスの団体が押し寄せてmatingしまくる
  • e.g., chimp, bonobo

2.5 community

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    • 一点集中でなく、トップダウンでなく、全てのパーツが独立して、自立して動いている組織。 それでいて全体でバランスがとれ、一つの目的に向かっている状態
    • male tends to be related
    • 中心にmales、周りにメスが散らばっている。
    • territorial defense by males.
    • males establish dominance hierarchy based on coalitions (by supported by other males)
    • mating pattern
      1. dominant male has preferential access
      2. promiscuity
      3. safari
        • メスがバレないように仲のいいオスのもとへ
    • テリトリーの境界線をパトロール中に他の猿を見かけたら殺す

  • male dominance hierarchy

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    • たくさんのメスが中央に。オスが周りを囲む
    • linear and agnostic male dominance hierarchy (based on fighting ability)
    • higher-ranking male has a priority of access to female
    • female forms matrilineal hierarchies.
    • e.g., Macaque, Papio
    • variations
      1. Saimiri
        • form all-male units and all-female units.
        • only in a breeding season, males get fatten and start competing each other.
      2. Mandrillus
        • females choose the dominant male

  • multi-level society

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    • single male
    • female dispersed
    • male wonders female to female
    • e.g., Pongo

※all apes in common is that females are dispersed

Nocturnal Mating Systems

  • not well known
  • most are dispersed, but social
  • solitary foraging
    • eat insects
      • also have varied diet like fruit, tree sap, and etc.
  • small (mostly less than 1 kg)
  • e.g.,
    • Lemur forms
    • Loris
      • slow metabolism (oxygen consumption: needed for burning energy especially when excising)
    • Aotus (night monkey)
  • most cases, birth generally coincide with warm/wet seasons.
  • litter size in this group does not decrease as body size increase.
    • irregular fluctuations in food supply and environmental hazard -> greater rates of reproduction (litter size and/or annual birth rate)
    • species living in relatively dry or cold climates seem to have relatively high reproduction potential.
  • smaller species breeds faster because it is more vulnerable to predators and climate extremes.
  • five types of social systems of Nocturnal primates
    • type 1: Cross between single male and exploded polygyny
    • type 2: Similar to Exploded polygony
    • type 3: "synterritoriality" - weird monogamy
    • type 4: separate male and female ranges
    • type 5: monotony

type 1: Galago senegalensis (Senegal bushbaby)

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  • adult male ranges are larger than those of females
  • matriarchies are present (related adult females with overlapping ranging areas)

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  1. females are highly territorial
    • they repulse other unrelated females
    • scent mark territory
    • vocalize location
  2. females are matrilineal (trace mother)
    • young stays in territory of mom.
    • move out when new territory open (mother in other group dies etc)
    • 他のグループのトップが死んだら、他のグループのメスがその座を奪いに来る
    • forage alone / sleep together
    • offspring do NOT defend territory
    • mom and kids interact
    • mom parks infant
      • problem: snake eats them
        • so, change in kids' behavior: still, quiet on tree
  3. Males are highly territorial
    • one dominant male over several female-group territories
    • young male is NOT territorial, but wonder around
      • disperse (オスの子供は追い出される)
      • move to a territory, and don't challenge resident male
      • when resident dies, other male takes over
      • territoriality is year round
        • breeding seasonを安心して迎えられるためにその前の時期に争いが起こる
        • to make sure to have an access to female when breeding season comes
  4. male and female form bonds

type 2: Pottos and Lorises

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  1. similar to Galago
    • but NO matrilineal hierarchies.
  2. females tend to disperse
  3. less territorial
    • little vocalization (i.e., quiet)
      • less socialize-able than Galago
    • scent mark
  4. infants are carried more often, but also sometimes are parked.

type3: Tarsiers: Synterritoriality: male and female are alone in same territory

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  1. call each other (チッチって感じの音で)
  2. male usually mates with local female
  3. male excursions (遠征)
    • (sometimes go out to find other female)
  4. some scent marking

type 4: Poorly-dispersed (other nocturnal primates)

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  • separate male and female ranges

type 5: Pair-bonded monogamy

f:id:astrobot:20111003011223j:image (other nocturnal primates)

Similarities in the Social systems of Nocturnal and diurnal species

  • larger species eat a relatively high proportion of fruit, which allows grouping, as opposed to insects, which seem to demand a solitary foraging technique in nocturnal species.
  • Nocturnal life is strongly associated with a small body sizel
    • high-energy diet
    • poor manipulative abilities
    • solitary foraging techniques
    • reliance on olfactory and auditory communication correlated with a smallter brain size in relation to body weight
  • Diurnal life
    • larger
    • more varied diet (including folivory)
    • improved manipulative abilities
    • gregarious foraging habits
    • reliance on visual acuity and color vision
    • accompanied by greater expansion of the brain
      • anthropoids have relatively larger brains than prosimians
      • diurnal lemurs have relatively larger brains than nocturnal species


霊長類行動学もくじ

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