Animal Behavior: Aggression

human infanticide

kids are more likely to be abused by a step-parent than a biological parent--whether or not adaptive is VERY controversial

storks

kill their youngest babies when food is scarce--eggs hatch asynchronously

example of aggressive behavior: interspecific competition over resources

lions & hyenas are aggressive in order to solve competitive issues for food

intersexual: male gulls attack female gulls

males give females a gift of fish; in order to avoid a girl just wanting fish, they attack her to ensure that she's there for the long run to mate, not just get a fish (used to think that males mistook females for other threatening males)

de Waal's fear grin

monkeys who grin the most are the most subordinate--monkeys who never grin are dominant

ex. 4: speckled wood butterflies

native always wins b/c territories are in the sun, so they soak up the energy to beat intruders; if remove original and put in a new native, the new one will beat the original b/c the original doesn't have the sun's energy anymore but the new one doe

territorial aggression

need just the right amount to protect yourself w/o spending too much energy

accuracy of data

not very accurate b/c could see a decline in number of kids & call it infanticide w/o knowing the cause of death

who gets killed?

only nursing babies b/c older ones don't bother the mom--males just need the mom to be receptive again

why do intruders even bother?

same reason we play the lottery--may be SOME possibility that they might win one day

controversy

some species that use infanticide don't have the social system that lions and langurs have, so why would they use it?

nest strategies of female digger wasps

some spend lots of time digging own burrow, some use burrows they see but risk fights b/c might not be empty of eggs & they don't bother to check

evidence that infanticide is adaptive

1. compelling in groups of females w/ 1 male like langurs and lions 2. male tenure is limited & so is mating opportunity 3. males don't kill their own infants

hawks vs. doves: ESS

-ESS = evolutionarily stable strategy -ESS is not optimal b/c would be better if all played shy like doves -this would make them vulnerable to invasion by a mutant hawk

self-restraint

-Lorenz said is for the good of the species -is really for individual: if use maximum power, could both just end up dying--not good for anyone -just need to show that you are stronger -selection minimizes cost to winner instead of maximizing cost on loser

coots

-have lots of babies but kill most when food is scarce -continue to have lots of babies JUST in case there would be a good year for food

why aggression?

-increase fitness via more resources or mates -improved reproductive outcomes -reduction in competitor's fitness

infanticide: unrelated babies

-lions: males kill other males' babies -squirrel & other rodents: kill other people's babies to eliminate competition & have more resources -langur monkeys: new male kicks out old male & kills all his babies so his females will mate again

bowl & doily spiders

-males are scarce, so females compete (?) -male fighting ability varies w/ body size -virgin more valuable; after 7 min. copulation, 90% of eggs have been fertilized -bigger males win fights; smaller males fight more when female is valuable; most serious fights are when cost and value are the same for both males

proximate & ultimate factors

-proximate (i.e. internal emotional state): not considered a factor in aggression b/c animals' brains are so different -ultimate: predation limits freedom & fitness, so is a form of aggression

examples

-rattlesnakes just wrestle (no fangs) -wasps don't sting each other -cichild fish display instead of chomp

ex. 3: black-winged damselfly

-thought could determine energy/ability by looking at thorax weight, but no pattern emerged -looked at fat content for an accurate predictor of available energy

definition of aggression by Wilson

A physical act or threat of action by one individual that reduces the freedom or genetic fitness of another

infanticide benefits the species?

NO WAY; dummy's explanation: humans are taking over habitats so animals need to shrink their populations (DUMB)

ex. 2: Yarrow's spiny lizard

aggression is very costly: with extra testosterone, is more aggressive; we know it's costly b/c testosterone + extra food survive more than just testosterone b/c get exhausted

pelicans

always lay 3 eggs, but SIBLICIDE: siblings knock 2 out of nest

agonistic

any aggressive interaction (including conciliation, retreat, or submission)

key to these birds

asynchronous hatching: results in different sized offspring (investment is in the older larger babies)

intrasexual aggression

b/w 2 females or 2 males (usually males fighting over female mate)

dominance hierarchies in chickens

can tell dominance and subordination by fighting success; need less than 10 chickens b/c chickens can't remember more than 10 so wouldn't have any sustainable hierarchy

intransitive relationships

circular (A>B, B>C, C>A) and TEMPORARY--eventually settle into linear transitive relationships that remain stable over time

this is an example of

facultative use of strategy b/c individual females use both strategies

intersexual: ring doves

girl needs boy courtship to become receptive; if girl is too eager, means she has already mated so new male attacks her, which delays her ovulation and increases his chances of fertilizing her eggs

ex. 1: golden-winged sunbird

turns aggression on and off: only protect flowers when producing intermediate pollen: protect territory in a facultative way

when do animals fight to death?

when reward is rare

indicators of dominance in primates

yawning, grooming, etc. are NOT indicators, but are correlates--can't look at every individual action, look at overall relationships