Primatology Exam 2

what impacts seasonal fluctuation

seasonality is dependent on rainfall, not heat

reduction in food intake - orang 85-90%, shifakas - 74%, gorilla - 20%, chimp - 46%

how do they deal with seasonal fluctuation

1. switch food, typically to lower quality

2. shifts in ranging, ranging in unknown areas —> increased energy expense (traveling farther), less efficient foraging (dont know area)

3. changes in grouping patterns, especially fission-fusion

dietary shifts are most common because the others have very high risks, but larger bodied primates are more likely to shift ranging patterns, lactating chimps seek shelter in caves to cool down

fallback food

anything consumed when the main food is not available

• negatively correlated with abundance of preferred foods

• allows for reproduction even in unfavorable conditions

reproductive seasonality

reproducing during certain seasons. most wild populations have at least some degree of reproductive seasonality

icome-capital breeding framework

an income breeder requires daily reaching of caloric intake; reproduction varies day-day

capital breeder can rely on fat when food is low, allowing for reproduction even when food is scarce

primates sit in the middle and can change their diet. Middle to late lactation usually falls with the greatest food abundance because it is very energy intensive

when there is a short time where females are fertile, there is no male competition because females cannot be monopolized

sentinel species

tell about the health of the ecosystem

flagship

charismatic megafauna

ecosystem services

species does a job, such as seed dispersal

spatial ecology

home range size and home range overlap

home range size

space the animal will use over a specific period of time; can change seasonally. typically larger with body size and males. group (cumulative) mass, instead of individual, influences range

arboreal species and overlapping ranges have more of a cumulative body mass relationship; frugivores have larger home ranges than folivores

infant carrying

unique to primates except for marsupials; hiding could be effective against predators in most species; large litters provide thermoregulatory benefits and makes them impossible to carry, so they are parked in nests

home range overlap

large level fission-fusion for predator defense; ecological knowledge + sharing of information for enhanced foraging; increased resource holding potential because of temporary larger group; reconnaissance before transfer (learn about another group before joining it; extra-group mating for genetic diversity

territory

portion of a home range actively defended

what influences territoriality

territorial males have a smaller range which is defended for use in mating, feeding, and all activities. It is more limited in primates than other mammals, which could be because it reduces the costly aggressive interactions

maintained through scent marking, patrols, visual rituals

simple optimality model for territoriality

predicts territory size has to be balanced by benefits and costs of defense. only species that can travel far enough ina. day to visit the entirety of their territory should be territorial

• chimpanzees are exceptions, they have large group size and fission-fusion which allows them to have a larger defended territory

mate defense hypothesis

monopolize a mate. contest shoul dbe higher when estrous female is present; high female-male ratio, males should her females, aggression should be largely intrasexual

male resource defense

males defend resources for females; dependent on habitat quality, so males are more territorial to monopolize it; more imprtant in single male groups

dispersal meaning and types

emigration from a social gorup

primary - from natal group

secondary - dependent usually on demographic levels

trends in dispersal

in mammals, male biased

in primates, female biased

costs and drivers of dispersal

primary cost: aggression from new group; minimized with parallel dispersal

drivers:

• ecological; lower food availability=leave; (chimps actually leave when food is more abundant)

• physiological - sex hormones (if leaving at sexual maturation)

• social: conspecific attraction (leave during mating season), agressive eviction (remove males from harem), reduced social integration (less grooming, avoidance)

why would you disperse?

inbreeding avoidance

local mate competition - sex that competes more strongly for mating opportunities should disperse

resource competition - pair bonded species - finite resources, only one breeding pair

why would you oppose dispersing?

hyperlocal knowledge of food resources

mortality costs

loss of kin cooperation

why is there female-biased dispersal in primates

dominant males have very long tenures, overlap between dominant father and daughter reaching sexual maturity

males benefit from kin cooperation - hunting and territoriality (ex: chimps)

collective action problem

coming to a consensus as a group

• pay something to be in the group, which is a cost to some; giving up selfish perspective

group size paradox

the larger the group the more likely they SHOULD be to make a decision, but in actuality collective action problems are more pronounced because each individual is more likely to defect

territorial defense becomes MORE of a problem as the group gets bigger

there are logical or informational constraints on getting the relevant individuals to act in concert (insufficient incentives to get individuals to participate)

solving collective problems

exploitation of the great by the small: most dominant makes the decisions (strongest/biggest/highest caloric intake = more incentive to move); highest rank leads efforts

dominance asymmetry, coercion, most knowledgable

dominance asymmetry in solving collective problems

individuals will follow others, so only x number of individuals are needed for the whole group to follow

coercion by dominant individuals in collective problems

Unlikely to work in practice because of the inability of a dominant animal to force a consensus decision, either because:

• It is physically unable to do so, particularly in large groups

• It would not gain sufficiently to outweigh the costs of coercion

collective problems solved by the most knowledgable

mostly in humans than nonhumans, but is seen in groups led by older individuals

consensus decision making

members of a group vote (different calls can mean different things); depends on rank and number of individuals voting.

individuals forego personal interests for group interests (reduced fitness); consensus costs can be so pronounced that they lead to segregation (breaking up of the group based on needs); they will stay together with. hugh predation because they have shared info and incentives

disagreements in initiators for which direction to go leads to anchoring where the group wont go in any direction

what influences who will take leadership

motivation - dependent on resource need; sexually dimorphic males = males have more motivation; females have to reproduce = more motivation; whatever is most energetically demanding = more likely to be leader

temperament - individuals who talk/vocalize more have more leadership potential

knowledge - age correlates with leadership in areas requiring specialized knowledge, but not when risk-taking or physical bravery are needed

dominance status - more resource holding potential

what is a social bond

interactions among individuals, relationship between them, social structure all relate to each other

top grooming partner - grooming exceeds time needed to remove parasites

strongest bonds are between kin; nonkin bonds are called friendships

poking eyes is a trust exercise between capuchins

how do we describe social relationships?

frequency, diversity, symmetry, tenor, tension, predictability, stability

what is the adaptive value of social bonds

in baboons, increases infant survival.

highest bonds are with mothers and daughters, and then sisters. females with more female bonds have higher survival rates

social bonds for males

strong bonds are tied to future dominance rank. dominance rank is tied to paternal success. so, social bonds are tied to paternal success

if bonds are not maintained, then neither is rank or reproductive sucess

social bond research topics

reproductive rate - if strong bonds are important, reproductive rate is higher

Offspring survival - more infants survive

Longevity - lifetime reproductive success or mortality based on long term social bonds

• The best predictor of how many offspring is how long they live

social relationships and mortality in humans

close social relationships help survival so much it can offset smoking

social support is good all of the time

access to resources, agonistic interventions, predator avoidance, stress buffering

stress buffering

glucocorticoids (stress hormones) are good in the short term because they bring stored energy into use. but, theyre bad in the long term because they cause decreased immunity, cardiovascular problems, and lower reproductive hormones

social interactions can decrease stress hormones and buffer against stressful situations

social stress and dominance rank

higher ranking individuals have lower stress hormones, especially for high ranking females (less competition, access to food)

• alpha male stress is higher depending on the stability of the dominance hierarchy; more unstable for males

intergroup encounters raise stress levels. even in acutely stressful situations, bond partners will reduce stress hormones

proximate mechanisms for social behavior

mate access, social status, stress buffering = higher success

what is cooperation

benefits recipient but can be costly or beneficial to the actor

mutualism

both actor and recipient benefit

altruism

benefit recipient and carry an immediate cost to the actor

what are some constraints of cooperation

cognitive constraints: keep track of costs and returns over minutes vs years

defector coming into a group will always have higher fitness than the cooperative population; due to breeding, overtime the whole group can become defectors and the grouo will fail

cooperative behavior in nonhuman primates

almost all of it is kin selection or direct reciprocity

benefit*degree of relatedness > cost

Who should you bias your behavior for based on relatedness alone?

the one with the highest percentage of your genes, typically your offspring

kin recognition is required for kin selection. how do they recognize?

close association and familiarity

depending on how many males (harem - offspring are all related vs multi male); fewer males (high reproductive skew) results in higher tolerance because it is more likely they are all siblings

phenotypic cues - olfaction in steps, owl monkeys

reciprocal altruism (direct reciprocity)

same individual must assist repeatedly; frequency they give is contingent on frequency they recieve; there are temporary net costs; it relies on payback AT SOME POINT; they cannot be close relatives or prospective mates

cheaters (ones who wont give and only take) must be detectable

sense of fairness

capuchins and chimpanzees are less likely to do work, exchange, or accept a reward if another individual got a better deal

indirect reciprocity

benefits are not gained from the individual helped, but from a third party observing the interaction. good reputation, feel good activity, a good reputation is more valuable than money

network reciprocity

cooperators form clusters where they can earn higher payouts than defectors

group selection

selfishness beats altruism, but altruistic GROUPS beat selfish groups

kin selection

choosing to support kin over all others

what are the types of altruism

kin selection, direct reciprocity indirect reciprocity, group selection, partner choice

all must weed out defectors, or risk the group falling apart

two kinds of sexual selection

1. males compete for a mate (intra)

2. females choose a male mate based on appearance (inter)

intersexual competition

mammalian females are usually the choosier sex

choose for: paternal investment, territory, good genes, maturity, dominance, weaponry (fighting ability and rank), male investment, symmetry, vocal displays, olfaction, heterozygosity

testosterone

males with high testosterone are more aggressive and more colorful

direct benefits

territory, provisioning, paternal care

indirect benefits

good genes, MHC diversity

good gene hypothesis

elaborate male traits may be indicators of heritable genetic quality; this relies on honest signals and handicapping traits.

males have a trait that reduces viability (ex: bright coloring), and survival despite this handicap indicates high quality genes, so females will mate with brighter colored males

with trait still have same lifespan and more offspring survive

sexy sons hypothesis

not often used in primates

trait has evolved beyond being an honest signal, decreasing the fitness of the male; females ONLY select so their sons have that trait and can get more mates

fisherian runaway selection; correlation between trait and female preference —> females choose the modified more dramatic signal over the real males

lifespan is shorter and offspring do not survive at a higher rate, but they do have more mating opportunities

compatibility hypothesis

mechaism for good genes: Major histocompatibility complex (MHC); selects for immune function

complementary or very different MHC proteins would enhance and offspring’s immune system, so mates are chosen to diversify immune systems

positive correlation between mating and different MHC; golden snub-nose monkeys are thought to have MHC-biased mate choice because their MHC is more diverse than it should be

what are the three hypotheses for indirect benefits

good genes, sexy sons, compatibility

polyandrous mating

females appear to go out of their way to mate with more than one partner (brown capuchins, ring-tailed lemurs)

pros and cons of polyandrous mating

risks: harassment from dominant males, STDs

pros: lower infanticide risk - if they dont know who the father is, they will think it is their own (paternity confusion)

• paternity confusion hypothesis: required that females cannot be monopolized; females can avoid being monopolized by unreliable timing of ovulation and sexual swellings

male mating strategoies

sexual coercion, reproductive concessions, consortships and mate guarding, male infanticide, male-female friendships

why are male-female friendships beneficial

females prevent infanticide and males get future mating opportunities

basic transaction model (concession model)

males can control reproduction but presence of subordinates increases fitness; they allow subordinates opportunities to mate in return for defending the group from loner males trying to overthrow the alpha

reproductive skew models; seasonal breeders?

basic transaction model and compromise model

seasonal breeders have minimal reproductive skew since females cant be monopolized

compromise model

dominant is unable to control reproduction and exclude subordinates; this decreases the groups productivity

male consortship and mate guarding

males that herd or maintain proximity to a female when she is fertile, are more likely to sire offspring

mate guarding is aggressive to other males, and is not female choice because all other choices are prevented. alpha male should choose older females who have high reproductive success

male infanticide

widespread convergent evolution, but most common in social species, and almost absent in pair bonding (callitrichids - one reason monogamy evolved)

occurs more with higher reproductive skew toward the alpha male, because subordinates know its unlikely to be their offspring, and with longer tenure length following takeovers

shortens period of postpartum infertility, allowing males to impregnate more females more quickly

female counterstrategies to male infanticide - evolutionary arms race

promiscuity - no one will know if theyre the father

stay in the proximity of potential defenders

female coalitions - work together to run off males too close to an infant

group splitting - when a takeover happens, those without infants remain and those with leave with the former resident male

Bruce effect

what is the bruce effect

if females are pregnant when a takeover happens, they spontaneously miscarry, which is thought to prevent infanticide

stress hormones increase and estrogen plummets when new male comes into the group

challenge hypothesis

the role of testosterone in male-male competition: musculature, armor, body sexual dimorphism, fear reduction, vigilance towards dominance-related behaviors. however, it is taxing on heart muscles, so it has to be tightly moderates to avoid death

mandrill face color is associated with high testosterone

testosterone should be the highest during mating season for seasonal breeders, or when competing for a fertile female

high rank predicts mating access, so high ranking males should have higher T

T is higher during group instability

sexual dimorphism + social mating groupings

larger dimoprhism = intense male-male competition, polygynous mating systems, low levels of male parental care

less dimorphism = social monogamy, higher levels of male parenting, less male-male competition, lower testosterone

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 and female size and traits are less pronounced

parental care

anything that is likely to increase the survival and fitness of young

parental investment

investment by parent that increase an individual offspring survival but at the cost of investing in other offspring (foregoing mating, reduced parental survival)

which offspring should be invested in?

healthier, bigger, younger individuals, and males because of reproductive asymmetry

when should offspring be invested in?

if benefit to parents is greater than the cost

1. future prospects of reproducing are low

2. successful rearing requires two parents

decrease investment if relative value of offspring is low, or presence of alloparents offsets costs

females have a lot of investment already at time of birth from carrying the fetus, so they will continue to invest

when are alloparenting and biparental care more common

when there are long periods of offspring dependency

orangutan interbirth interval

8-9 years

life history stages

infant - until weaning

juvenile - until puberty

adolescence - puberty

adult - first reproduction

maximum life span drive reproductive success in females

r selected

many offspring with low investment and low survival (RABBITS)

k-selected

few offspring with high investment and high survival (KANGAROOS)

primates are K selected

Slow life histories, altricial (needy) offspring, single births (except streps), long gestation

how long is elephant gestation

2 years

why is childhood unique to humans

adults still provision for children, while juveniles in primates do not get provisions after weaning

male vs female metabolic expenditures

energy is finite and must be spent on somatic functions (growth + maintenance), survival, and reproduction

males sacrifice growth for energy to spend on play

females play less so they can use more energy for growth, and reach adult body size faster

major adaptive hypotheses for play

motor skills, training for the unexpected, social skill development

why do males play more

motor skills are needed to defend a territory/females and move to the top of the dominance hierarchy

unexpected physical altercations

formation of social bonds - philopatric sex might play more

factors influencing primate life history

mortality rate, infanticide risk (if high, mothers might accelerate weaning), diet (+seasonality), encephalization

natal coats and infanticide

natal coats signal to group members that infants should be treated differently (oddity efect)

cryptic color to avoid predation

warmer for heat retention

infanticide is a driver of neonatal coloration change, as mothers will wean earlier to change the coat color so theyre not targeted

ecological risk aversion hypothesis

assumes that juveniles are less efficient foragers and position themselves near conspecifics to avoid predation, and thus experience high levels of intragroup feeding competition

evidence supports that they occupy central positions, but by weaning they already have adult foraging abilities

needing-to-learn hypothesis

correlation between brain size and reproduction age - essential skills are learned during development and required for adults

opportunities for socialization and long term relationships

why do primates have a protracted juvenile period

social skills development

needing-to-learn

ecological risk aversion