霊長類行動学3. 霊長類社会構造(Social Structure)
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.
gregarious (with others): e.g., oysters | solitary |
social (interact with others) | asocial: e.g., tiger |
- all primates are social
- most primates are gregarious
- nocturnal animals tend to be solitary
- orangutanはsolitary 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
- Multimale / multifemale
- The group consists of more than one adult female and more than one adult male and immatures
- 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
- 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
- Community: similar to fission-fusion; however, subgroups are more dispersed and less likely coalesce into full group
- The group consists of more than one adult female and more than one adult male and immatures
- Unimale / multifemale
- a cohesive group consisting of one adult male and more than one adult female and young
- Unifemale/multimale
- a cohesive group consisting of one adult female and more than one adult male and young
- Two-adult group
- a cohesive group consisting of aone adult female, one adult male, and immatures.
- 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.
- Multimale / multifemale
- Solitary
- group (gregarious)
- any size
- male and female / male only
- why do they form groups?
- group size broadly correlated with habitat especially its size.
- Dispersal
- leave natal group
- exogamy(族外婚)
- most primates, females stay in the group (male transfer / maternal line)
- except human, chimp, bonobo, orangutan (female transfer / paternal line)
- and only human keep kin relationship when they left the group
Territorial
- 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
- defend territory like chimp
- 2 reasons (to guarantee the following 2 resource abundance)
- food
- mating
- 2 reasons (to guarantee the following 2 resource abundance)
breeding system (mating patterns)
- Grouping pattern does not equal mating pattern for most primates.
- mating and rearing systems are a prime factor in social organization
- monogamy: one female and one male mate exclusively during mating period
- serial monogamy (一生同じ相手だとは限らない。): characteristics of humans (Homo)
- life time monogamy: e.g., Callicebus
- pair bonding: attached each other - e.g., tidy monkey
- polygamy
- polyandry: one female mates with multiple males during mating period
- polygyny: one male mates with multiple females during mating period
- polygynandry: females and males mate with multiple partners during mating periods
- promiscuity
- community
- fission-fusion
- male dominance hierarchy
- multi-level society
- exploded polygyny
1. monogamy
- 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
- serial monogamy (一生同じ相手だとは限らない。)
- characteristics of humans (Homo)
- life time monogamy
- e.g., Callicebus
- pair bonding:
- one type of monogamy
- attached each other (not only the reproductive way, but also for the life)
- e.g., tity monkey
- serial monogamy (一生同じ相手だとは限らない。)
2. polygamy
- more than one partner
2.1 polyandry(poly- many, andras- man / 一妻多夫制)
2.2 polygyny(poly - many, gyny - "female" /一夫多妻制)
- single male and multi-females
- small group size (2~3 females)
- resident male gets "tenure" in terms of reproduction
- peripheral males have strategies to get a reproductive chance
- cryptic way
- e.g., Guenon (Cercopithecus: African monkey live in deciduous-rain forest), Cercopithecus mitis
- multi-male influx
- maleのグループで押しかけ、resident maleを脅して追い出す。
- cryptic way
- peripheral males have strategies to get a reproductive chance
- age-granded
-
- 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
- multi-male / multi-female
- both male/female has multiple partners
- e.g., Brachyteles arachnoides
2.4 promiscuity
2.5 community
-
- 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
- e.g., Pan
- 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
- dominant male has preferential access
- promiscuity
- 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
-
- 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
- Saimiri
- form all-male units and all-female units.
- only in a breeding season, males get fatten and start competing each other.
- Mandrillus
- females choose the dominant male
- Saimiri
-
- e.g., Theropithecus gelada, Papio hamadryas
- one male units (OMU)
- consisting of one male with multi-females (avg. size is 2.4)
- set of OMU form Band
- basic societal unit
- set of Band forms Herds.
-
- 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
- variable social systems
- solitary foraging
- eat insects
- also have varied diet like fruit, tree sap, and etc.
- eat insects
- small (mostly less than 1 kg)
- e.g.,
- 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: Galago senegalensis (Senegal bushbaby)
- adult male ranges are larger than those of females
- matriarchies are present (related adult females with overlapping ranging areas)
- females are highly territorial
- they repulse other unrelated females
- scent mark territory
- vocalize location
- 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
- problem: snake eats them
- 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
- male and female form bonds
type 2: Pottos and Lorises
- similar to Galago
- but NO matrilineal hierarchies.
- females tend to disperse
- less territorial
- little vocalization (i.e., quiet)
- less socialize-able than Galago
- scent mark
- little vocalization (i.e., quiet)
- infants are carried more often, but also sometimes are parked.
type3: Tarsiers: Synterritoriality: male and female are alone in same territory
- call each other (チッチって感じの音で)
- male usually mates with local female
- male excursions (遠征)
- (sometimes go out to find other female)
- some scent marking
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