Primate 2

Optimal foraging theory

Make predictions about how an animal should forage (focused on protein or energy maximization)

Energy maximization

High energy intake = high quality diet

Protein maximization

Fruit (not enough protein), insects (not enough protein for larger species, they consume leaves instead)

Secondary metabolite avoidance

Some compounds produced by plants during metabolism can be harmful to animals (toxicity of plant secondary metabolites (PSM) depends on the amount consumed & physiology (Tannins - can bind with plant proteins to form indigestible complex)

Regulation of fiber intake

Most animals lack the enzymes to digest cellulose, hemicellulose, & lignin - relying on microorganisms (some folivorous primates deal with the digestive limitations by selecting leaves that are rich in protein but relatively low in fiber)

Foraging tradeoffs

Cost: time & energy to locate & digest foods - benefit: nutritional value

Foraging efficiency

How much energy an individual can consume, relative to the energy required to move to another feeding site

Trends for fruit-based diets

Primary cost: reliance on fruit —> larger day ranges &, therefore, increased metabolic requirement; primary benefit: fruits are a higher-quality, more readily digestible food —> digestive processing is minimized

Trends for leaf-based diets

Primary cost: Leaves are a lower-quality resource, which requires more digestive processing; primary benefit: reliance on leaves —> shorter day ranges & therefore, expend less energy in travel each day

Scramble competition

1st come, 1st serve (foods evenly distributed)

Contest competition

Some individuals systematically exclude others and obtain more of the resources (foods distributed in patches)

Behavioral adjustments to seasonality

Switching foods, shifts in ranging patterns, changes in grouping patterns

Flexible grouping: fission-fusion dynamics

Members of the community are rarely, if ever, together; subgroup size and composition vary over time; preferential associations

Fallback foods

Generally used to refer to abundant foods of relatively low quality used during periods of low overall food availability, negatively correlated with abundance of preferred foods

Reproductive seasonality

Timing of reproductive events in relation to food availability frequently characterized using the income-capital breeding framework

Ecological constraints hypothesis

Often suggested that being in large groups is inherently beneficial, such that group size is predominantly explained by the costs of sociality; primary benefit: reducing predation risk; primary cost: increased competition

Measure the costs of being in groups

Foraging effort, day range, physiological metrics

Optimal group size hypothesis

Intermediate group size is favored as it reduces food competition & provides increased safety from predators

Foliovores paradox

Several folivorous species defy expectations that they should live in larger groups, since food competition is less pronounced & predation risk is high; folivores form smaller groups than similarly sized frugivores, larger groups travel longer distances, & spend more time feeding, suggesting scramble competition; resolving the paradox: social factors (male harassment & infanticide), & multiple transfers may keep group size more optimal (in optimal group size theory), scramble competition

Home range

The entire area that an animal (or group of animals) uses over a specified time period (usually annual)

Day range

The distance that an animal (or group of animals) travels in one day

Territory

The portion of a home range that is actively defended

Infant carrying

Carrying infants while foraging is rare in eutherian mammals but common in primates; it appears to have evolved several times independently & remains once evolved; monkeys & apes are habitually carried, whereas parking behavior is found throughout strepsirrhines - species with larger litters were more likely to use nests to park their infants

Territoriality

Defended for use in mating, feeding, or all activities (all-purpose), theoretically reducing the need for costly aggressive interactions, usually maintained through scent-marking, patrols, visual rituals, etc.

Index of defendability

Populations (or species) can only defend territories when they can access all parts of the range on any given day

Mate defense hypothesis

Contests should escalate more: (1) when estrous females are present, (2) when the female-to-male ratio is high, & (3) males should herd females; also, aggression should be largely intrasexual

Male resource defense hypothesis

Male responses should vary with territory quality & location in the range, resource defense demonstrated an important strategy in groups with one male, received less attention in multi-male groups

Resource holding potential

Measure of the ability of an animal to win a contest if the participants adopt the same strategy

Dispersal

Primary cost: aggression from resident conspecifics, strategies that might attenuate that aggression include parallel dispersal & dispersing into groups with former group mates

Proximate drivers of dispersal

Ecological (reduced food availability), physiological, social

Conspecific attraction

Preference to disperse during the mating season

Aggressive eviction

Emigrations usually occur during breeding season, aggression increases toward immatures & during takeovers

Reduced social integration

Higher asymmetry of grooming before dispersal

Resource competition hypothesis

Predominant force in birds

Local mate competition hypothesis

Sex that competes more strongly for mating opportunities should disperse

Inbreeding avoidance hypothesis

In polygynous species (usually mammals), male bias is expected for two reasons: (a) local resources important to female reproduction & (b) male-male competition is strong

Factors opposing dispersal

Mortality costs, loss of familiarity with natal area, loss of kin cooperation

Factors favoring dispersal

Spatiotemporal variation resources, avoid kin competition for mates (LMC) or resources (LRC), inbreeding avoidance

Collective action

When individuals coordinate activity (problems in achieving cooperation when the best move from a selfish point of view does not produce the best collective outcome)

Group size paradox

Collective action problems are more pronounced in larger groups, defections by single individuals have a relatively small impact on success

Solving collective action problems

‘Exploitation of the great by the small’ (small group hunts, free riders get scraps) & consensus decision making

Leadership & motivation

State-dependent individual-based models predict that the one with lower energy resources spontaneously emerge as a leader

Leadership & temperament

Extraversion correlates highest with leadership emergence, & this trait (an indication of boldness) has a substantial heritable component

Leadership & knowledge

Individuals with superior information can guide groups to attractive resources

Leadership & dominance rank

In species with dominance hierarchies, dominant individuals often take leadership roles

Constraints on kin bonds for males

Typical dispersal patterns can limit male-male bonds among kin (even non-kin in species with secondary dispersal)

Main (direct) effects hypothesis

Social support is beneficial all the time (access to resources, help in agonistic interactions, help in predator avoidance)

Buffering hypothesis

Social support is mostly beneficial during stressful times (expect higher-ranking individuals to have lower stress hormone concentrations)

Cooperation

Behaviors that benefit the recipient but can be either costly or beneficial to the actor

Mutualism

Cooperative behaviors that benefit all parties

Altruism

Cooperative behaviors that benefit the recipient but carry an immediate cost to the actor

Hamilton’s rule

Provide help if br > c (b = benefits; r = coefficient of relatedness; & c = cost), requires kin recognition mechanisms to be relevant for paternal relatives

Familiarity

Close association early in life facilitates recognition

Reciprocal altruism

Altruistic behavior will be a function of the probability that the recipient will reciprocate (repeated interactions between two individuals, must require conditional retribution, cheaters must be detectable, short-term cost to the giver & benefit to the recipient)

Indirect reciprocity

Cooperative behavior between two individuals that does not depend upon their direct interaction

Reproductive skew models

The dominant individual must balance reproductive access & ensure subordinate males stay

Concession model

A dominant individual can control reproduction but the presence of subordinates increases fitness; the dominant offers “staying incentives” in the form of opportunities to reproduce in the group (albeit at a lower level)

Compromise model

The dominant individual is unable to control the reproduction of subordinates completely; the degree of reproductive skew is an outcome of struggles between the dominant & subordinate, & this struggle decreases group productivity

Sexual selection

Selection for male competitive ability & selection for female mating preferences

Female preferences in mammals

Maturity, dominance, weaponry, aggression, coloration, testosterone, male investment, symmetry, vocal Displays, olfactory displays, heterozygosity, genetic dissimilarity, & compatibility

Sexy sons hypothesis

Correlation between a trait & female preference: the trait can evolve way beyond being an honest signal; the trait itself can become a fitness burden; the process can therefore come to a point where the ONLY benefit to female choice is that her sons inherit the most attractive trait

Good genes hypothesis

Elaborate male traits may be indicators of heritable genetic quality (fitness), honest signals; males may have a heritable trait that reduces viability, but males with good genes can survive the handicap

Complementary genes hypothesis

Major histocompatibility complex (MHC): a group of genes that code for proteins found on the surfaces of cells that help the immune system recognize foreign substances; dissociative mating can maintain MHC diversity

Polyandrous mating

Females appear to go out of their way to mate with more than one partner; risks: harassment from dominant males, sexually-transmitted diseases

Male consortships & mate guarding

Males maintain proximity, groom & often mate-guard; consorting males are more likely to sire offspring

Male infanticide

Widespread in mammals; appears to have evolved convergently; most common in social species, less common in solitary species & almost absent in monogamous species

Sexual selection for male infanticide

Benefits to male: shortening the period of postpartum infertility, accelerating estrous, increasing mating opportunities

Bruce effect

An increased rate of abortions or miscarriages is reported following male takeovers, assumed rare

Larger sexual dimorphism

Intense male-male competition, polygynous mating systems, low levels of male paternal care

Correlates of paternal care

Social monogamy in species with long-term pair bonds, territoriality in which groups defend an exclusive area, reduced sexual dimorphism when the difference between male & female size and traits are less pronounced

Parental investment

Any form of parental behavior that is likely to increase the survival and fitness of young & decreases the parent’s ability to invest in future reproduction

Parental investment theory

Parents should invest in offspring whenever the benefit to themselves is greater than the cost to themselves

Increased probability & investment

Parents’ future prospects of reproducing are low if successful rearing requires two parents

Evolution of Paternal Care

Paternal care should evolve when the benefits outweigh the costs

What is paternal care for

Offspring survival & mating effort

Primate development

Stages (infant - until weaning, juvenile - weaning to the start of puberty, adolescence - puberty, adult - capable of reproduction)

Life history trends

Relatively slow life histories in general, relatively altricial compared to other mammals, single births

Factors influencing primate life history

Mortality risk, diet, encephalization

Extrinsic mortality

Risk of death that is not dependent on an organisms behavior

Intrinsic mortality

Risk of death associated with how an organism allocates resources towards somatic & reproductive effort

Infanticide & life history

Infanticide risk is high - some evidence suggests mothers accelerate weaning