Social behaviour and mating systems

Sociality

When individuals of the same species associate with each other beyond mating and parental behavior

Asociality

Species that come to together only for

-Mating

-mother-neonate relationships

Eusociality

Obligately social animals

-cooperation of young

-Reproductive castes

-overlap of generations (offspring help parents raise siblings)

Reproductive castes

Feature of eusociality

- division of colony into individuals who can reproduce/cannot

-Nonreproductive members caring for reproductive nestmates

-eg. naked mole rats

Altruism

unselfish regard for the welfare of others

-Behaviour appears to be costly to the "giver" but is beneficial to the "receiver"

-vampire bats sharing food

-alarm calls

Social thermoregulation

Communal nesting/denning/roosting aids in maintaining heat for numerous species in

winter

Reproductive output

Increased success at rearing young via provisioning

-parents improve offspring survival by providing them with resources

Communal learning environment

Information of survival tactics are shared to members

-primates

-dolphins/ orcas

-Meerkats

Costs to living in groups

-Competition

-Disease

-conspicuousness (not hidden, easy to see, attract attention)

-aggression

-interference (offspring killing)

Selfish/spiteful behaviour

-aggression over territory

-infanticide

mutualism

A relationship between two species in which both species benefit

selfish herd

individuals within a population attempt to reduce their predation risk by using others as a shield to increase their own reproductive success

dilution effect

as the number of individuals in a group increases, the chance of being the one attacked by a predator decreases

Confusion effect

Decreases predation when predators have difficulty in picking out a prey from the crowd (similarities between individuals via patterns causes confusion)

Kin selection

evolutionary strategy where animals help close relatives reproduce, even at a cost to themselves, because those relatives share their genes. It proposes that individuals can increase their genetic success via altruistic behaviours so their relatives can reproduce, as this spreads the genes they have in common

-Warning calls to alert for predator

Natural Selection

differential reproductive success of individuals in nature based on heritable characters

direct fitness

number of offspring the individual procreates

indirect fitness

number of offspring generated by the genetic relatives of the individual

-the reproductive success of its relatives, weighted by their genetic relatedness

inclusive fitness

sum of direct and indirect fitness

-total measure of an individual's genetic success, which includes both their own reproductive success and the success of their relatives, because they share genes

reciprocal altruism

Altruistic behaviour featuring a delayed benefit

-recipient returns favor in the future

greater chance in:

-long lived animals

-low dispersal rate

-clumping of individuals

eg. vampire bats

Darwin on Sexual Selection

differential mating success of individuals based on heritable characters

-Intra sexual competition

-Inter sexual choice

Intra-sexual competition

members of the same sex compete with each other

Inter-sexual choice

choice by members of one sex for particular mating partners of the opposite sex

-females choosing males

sexual dimorphism

Differences in physical characteristics between males and females of the same species.

-can evolve when selection favors that the expression of a character is different between females and males

-shape, size, canines, color

Fisher's Runaway Selection

Secondary sexual trait expressed in one sex becomes genetically correlated with a preference for the trait in the other sex

-not linked to fitness in the selected sex

primary sex characteristics

the body structures that make sexual reproduction possible

secondary sex characteristics

nonreproductive characteristics that develop from hormones

Bateman's principle

The idea that, since eggs require greater energy to produce than sperm, females should be the choosier sex and this should result in greater variance in the reproductive success of males.

-females selected to be choosy

-males selected to mate as often as possible

Triver's Parental Investment Theory

-Differential parental investment drives sexual selection

-Anything a parent does to increase probability of offspring survival to reproduce later onat the cost of the parents ability to generate more offspring

Polygyny

One male, several females.

monogamy

one male one female

-rare, <5% of mammals

Promiscuity

many males, many females

-neither sex can monopolize the other

-opportunity for multiple matings

Polyandry

One female, several males.

-1 female monopolized many males

female defense polygyny

males monopolize aggregations of females directly

-males defend a "harem" of females

-Extreme sexual dimorphism

-

resource defense polygyny

males defend territories rich in resources that are used by females

-resources are clumped spatially

Environmental Potential for Polygyny (EPP)

the degree to which the social and ecological environment allows males to monopolize females as mates

-if resources or potential mates are clumped in a non random way then polygyny is likely to evolve

-it is a predictor for potential for polygyny to evolve in a given habitat

-It refers to the environmental potential for polygyny

Peripheral Male Strategy

Low quality male will try to blend in with high quality males and mate with a female

female mimicry

Some small, inferior males mimic females; Dominant males don't chase them away and they get access to females (better able to sneak)

Alliance formation

Individuals that maintain long-term cooperative relationships with each other

Lek polygyny

Males display in territories to attract females (leks)

-females visit and pick a lek

scramble competition polygyny

Males outrace rivals to receptive females. Highly mobile males have higher copulatory & reproductive success

facultative monogamy

monogamous depending on the circumstances or conditions

-female densities are low, males settle for one

obligate monogamy

investment from male is required in order for female to raise offspring

sperm competition

a form of sexual selection that arises after mating, when males compete for fertilization of a female's eggs

Why is sperm competition favored for cetaceans?

because they can't monopolize underwater

fluctuating asymmetry

deviations from bilateral symmetry in paired traits

-reflects inability to maintain developmental homeostasis

-low food quality/ quantity

-pollution

-parasites, diseases

-genetic defects

Zuk Hypothesis

Hypothesis that is Sexual attractiveness is linked to health and immunity. Proposing that ornamental traits evolve as honest signals of parasite resistance and overall genetic fitness

-predicts females will select males with sexual selective traits that reflect infection and resistance (resilience)

-Predicts males that are infected will have reduced sexual selective trait intensity (weak/sick)