mammalian 5-benefits of group living

two examples in monkeys to show mammals dont always have group living to hunt for bigger prey

-golden lion tamarind, insectivorous, forage in groups as share info and learn. -hamadryas baboon split up in small groups and look for food sources share information about where they have been successful in finding food

within pride relations.

-in pride males related to each other, females also, but males and females are unrelated.

what percent mammals are socially monogamous

5%

main survival benefits of group living

Avoiding injury and disease Avoiding predation Securing a food supply Minimising energy loss

what part of mammals is caregiving young common in?

Canids

male lifetime repro succes in lions affected by what?

Coalition size Length of time resident in prides Total number females in prides

examples of group living to avoid injury and disease

Difficult to demonstrate Social grooming most obvious example Wolves frequently injured by larger prey; fed by other pack members

main reproduction benefits of group living

Finding and competing for a mate Rearing offspring and care giving Producing offspring of optimal number, sex and quality

if living in a group for reproductive benefits they must outweigh the costs of group living such as..

Increased competition for resources aggression risk of disease

reason in Serengeti lions that group living reduces infanticide

Males leave pride when 3 years old During next two years reach adulthood Males usually only hold pride for 2-3 years Competition between males rare - want their group to help them hold their pride. Work together to hold a pride. Injuries reduce chances of them all in holding pride against other males New males kill existing cubs when they take over a pride 27% cub mortality below 12 months due to infanticide Killing cubs brings females back into oestrus

examples of group living to minimise energy loss

Many species of bats and ungulates form groups to reduce energy loss there is not necessarily any social structure in bats Ungulates such as musk ox and bison huddle together during periods of adverse weather to reduce heat loss

example in lions of how in group living species, the benefits of group living outweigh the costs

Nomadic females do not live as long as pride females, produce fewer cubs, fewer survive. Disadvantage to females not being part of a pride.

lion female= cub production ecology

Pride females tend to produce cubs synchronously Synchronous births enable communal suckling of cubs Females preferentially suckle most closely related cubs Nomadic females do not live as long as pride females, produce fewer cubs, fewer survive. Disadvantage to females not being part of a pride.

theories on how mammalian social groups evolved

Probably semi-social route: Individuals from same generation formed aggregations, some became helpers guess: if environment is HOMOGENOUS??, tolerance to conspecifics evolved if environment is fluctuating, heterogenous exploitative behaviour occurs (e.g. naked mole rat)

role of resource dispersion in mating in groups

Resource dispersion promotes sexual segregation and polygyny females are driven by resources, male distribution mapped onto where females are as they are the 'limiting resource'

most efficient way to asses costs and benefits of group living

Selection operates at individual, not group level During its lifetime, we assume that an individual must attempt to maximise its fitness

3 ways animals use group living to avoid predation

Using other animals as cover Using other animals as an extended information system -Within own species -Mixed species e.g. baboons and antelopes (as babbonns have good eyesight, antelopes have good heaing) Group defences

so do male lions gain increased repro 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 to form non-kin coalitions

packer and pussey 83 exp.

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 So females best to live in moderate-sized pride before costss of group living overtake.

examples of group living to secure a food supply in uncooperative hunters

badgers= Defend group territories which have enough patches for a year round supply of food for each individual

why is group living not found in cats other than serengeti lions even though infanticide is also common in other species?

benefits of reduced infanticide don't outweigh the costs of group living-foraging etc.

Do all animals that hunt together have a relationship (Kin or share a territory)?

common but not always e.g. canadian otters males cooperatively hunt example of mutualism not a kinship

assumption that social systems are optimal for the environment has what asumption as a consequence?

different social systems should evolve in different environments

example of how marine mammals may live together to avoid injury

dolphins stay with injured or ill ind. with supplementary feeding e.g. observed in orcas, and helping them breathe

why is mate distribution driven by female distribution?

females are limiting resource

what features of behaviour do group living mammals show as group defense against predators?

help defend young show mutual assistance (if there is permanent composition in the group) groups modify behaviour (e.g. in open areas spread out) adjust group size (e.g. rhesus macaques (in habitat with lots of predators form large groups) with complex defenses (e.g. dwarf mongooses use sentries)

when is mutual assistance in predator avoidance shown?

if a distinct group and there is a level of permanent composition -In springbok no permanent composition so they scatter

case study of how group living enhances reproductive sex (offspring of optimal number, sex and quality)

in lions social system are adapted to diff. habit types e.g. etosha lions in groups to hunt successfully, Serengeti lions in groups to reduce infanticide

how is it known that in serengeti lions group living is to reduce infanticide and not to aid in prey capture

it was observed (by Packer and Pusey 83) that if prey were scarce females were solitary, if prey were abundant, group size had no effect on hunting success.

example of other unique benefits to securing a food supply from group living

kleptoparasitism of lions kills in hyenas

rearing offspring and caregiving in groups example

meerkats

talk about mating systems and how they affect group living

monogamy- Male has exclusive mating rights, guards and invests in young Long term pair bond - e.g. elephant shrews and dik-diks polygyny- Reproductive skew for males Try to produce quality males with high reproductive success e.g. Fallow deer, red deer

is the general rule for group living that the bigger the group the less chance of predation?

no there is an optimal size (e.g. gazelles, if theres too many they trip over each other when trying to escape predators)

cooperative hunting in mammals general trends

normally larger prey, larger group size NOT ALWAYS e.g. golden lion tamarind normally hunters are related

technique used by packer and pussey to test their theory?

playback experiments

why is female distribution driven by food sources?

raising young is energetically expensive, food is the limiting resource

what is the most common social system in mammals?

solitary

two groupings of benefits of group living.

survival reproduction

so optimal groups size in general depends on what two main factors

the environment and current circumstances

Why would an animal live in a group?

when the benefits outweigh the costs.

examples of group living to secure a food supply in cooperative hunters

wolves= Common for group size to be related to size of prey 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

is female mate choice important in mammals?

yup many primate males cant take over harem without support of females (common langurs) there is cuckoldry in some species (elephant seals) female pronghorn antelope also choose males with the best territory.