Mammals 5- benefits of group living

Examples of species which benefit from group living by Rearing offspring and caregiving?

-Mongooses e.g meerkats -African wild dogs -Wolves

how did Packer and Pusey (1983) test hypothesis on female serengeti lions living in groups to enhance repro success?

-Playback experiments: known lions = no response, unknown lions = females distressed and tried to hide cubs. -analysed lifetime reproductive success of Serengeti lions: for females, cub survival most important factor -Group living by females added to reproductive success - was highest in groups of 3-10 lionesses

examples of how group living helps avoidance of injury and disease

-Social grooming (decreased ectoparasites) -Wolves frequently injured by larger prey; fed by other pack members -Dolphins will stay with injured or ill individuals: Even helping them to breathe by bringing them to the surface if needed

example of an animal that hunts in a group but isn't kin or share a territory

Canadian otters: Males cooperatively hunt- Example of mutualism not kinship

Example of when a group size is so large it results in increased predation risk

Caribou. Too large and individuals trip over one another when running- easier to get taken by wolves

describe relationship between group living, resources and finding and competing for a mate

Female dispersion affected by distribution of resources. Males dispersion affected by female dispersion. If resources clumped, females will be clumped and one male wants control (vs monogamy)

2 types of monogamy- which is most common in mammals?

Genetically monogamous (rare) Socially monogamous- some cheating (more common)

Reasons for lions living in groups varies depending on..?

Habitat. Have a flexible social structure.

How is group living important for repro success of elephant seals

Harem dominated by one male. - outsider males sneak matings:if high quality male, female accepts, but if low quality male, the female will make noise and the harem male will intervene.

what do hyenas benefit from group living (in terms of securing food supply)?

Kleptoparasitism - parasitism by theft Hyenas will try to steal lions kills When enough hyenas near kill they will bundle in and take the kill of the lion

main reason why Etosha lions live in groups?

Live in groups to hunt successfully Original hypothesis for why lions live in groups

factors which affect male lions repro success

Male lifetime reproductive success greater variation than females (expected for a polygynous species). Affected by three main factors: -Coalition size -Length of time resident in prides -Total number females in prides

Benefit of infanticide to male lions?

Males only hold pride for short amount of time (2-3 years)- Reproductive life of a male only 33 months. Want maximum opportunity to have cubs before lose pride- Killing cubs brings females back into oestrus.

Example of animals which benefits from group living by minimising energy loss

Many species of bats and ungulates . e.g musk ox and bison huddle together during periods of adverse weather to reduce heat loss

describe how the repro stratedgy of male hoary marmots changes depending on density

Mate guarding if density high. Searching for other mate if density low b/c less chance of female being taken by another male.

which paper studied serengeti lions?

Packer and Pusey (1983)

How does group living enhance reproductive success in serengeti lions?

Pride females tend to produce cubs synchronously = communal suckling of cubs (allo-suckling) Nomadic females do not live as long as pride females, produce fewer cubs, fewer survive. Disadvantage to females not being part of a pride. Live in groups to reduce the risk of infanticide (optimum pride size = 5-6). 27% cub mortality below 12 months due to infanticide. (above 12 months cubs usually ok)

what do Hamadryas baboons benefit from group living (in terms of securing food supply)?

Split up in small groups and looks for food sources Share information about where they have been successful in finding food.

describe factors effecting optimal pride size of serengeti lions for females

Too small = not enough protection Too big = too tempting for other males, so there will be lots of take-overs

How does group living help individuals avoid predation? give some examples

Using other animals as cover. e.g bunching of baboons in vulnerable environment Using other animals as an extended information system: -Within own species e.g mongoose sentries (detect 98% air attacks and 100% ground attacks. groups <5 = can't have sentry and won't survive). -Mixed species e.g. baboons and antelopes (baboons = good eyesight but bad hearing antelope visa versa). Defence of young e.g elephants and musk ox. Mutual assistance e.g when hyena attack zebra, stallions kick hyena and females come together

How did mammalian social groups initially evolve?

We don't really know! Probably semi-social route: Individuals from same generation formed aggregations, some became helpers. Best guess: If environment: -Heterogeneous, animals tolerate conspecifics -Fluctuating, exploitative behaviour (e.g. naked mole rate)

do male lions gain increased reproductive success from group living?

Yes: 0.64 more cubs per extra male in the coalition survive for every extra member of male group Solitary males significant disadvantage: so need form non-kin coalitions

what do Golden lion tamarins benefit from group living (in terms of securing food supply)?

an copy other members finding food and hunt in the same places.

Common relationship between group size and size of prey- use wolves as example.

bigger prey = bigger group. European wolves hunt small prey (sheep and roe deer) tend to be solitary North American wolves hunt large prey (white tale deer) pack size 5-6, (bison) pack size 12-15 Why? If animal is not getting enough food in pack, better off alone.

what determines optimal group size?

depends on the environment and circumstance: changes benefits vs costs