Aggression

Question 1

Aggression (Wilson)

Answer 1

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

if both individuals live –> how to measure genetic fitness?

Question 2

Agonistic

Answer 2

refers to any activity related to fighting, whether aggression, concilation, submission, or retreat

Question 3

Self-restraint in aggressive behavior

Answer 3

• widely held to be trait that evolved for the good of the species
• ex. snakes X biting, just slamming head to ground per “rules of the game”

Question 4

What regulates aggression?

Answer 4

• if goal of aggressive interaction is to win w. maximum fitness gain, best way to win is for winner to minimize costs to itself and NOT to maximize costs to loser
• continuing attack when not necessary to gain inventive adds risk
• Why not cheat? –> retaliation (nature of display makes cheating difficult)

Question 5

Costs of aggressive behavior

Answer 5

• potential injury
• time & energy

Question 6

Benefits of aggressive behavior

Answer 6

• contextually dependent
• increase individual fitness through access to resources/mates
• improved reproductive outcomes
• reduction of competitor’s fitness

Question 7

Aggressive behavior types

Answer 7

• interspecific competition over resources
• territorial aggression
• dominance behavior
• sexual aggression (intra- & intersexual)
• infanticide
• parental aggression
• sibling aggression
• predatory/anti-predator aggression

Question 8

interspecific competition over resources

Answer 8

hyenas vs. lions over food & beyond

Question 9

Questions concerning territorial aggression

Answer 9

• why?
• benefits?
• how big territory?
• year-round vs. seasonal
• time/energy?
• qualities to determine contest winner?
• which sex defends?

Question 10

Yarrow’s spiny lizard

Answer 10

• increased T in lizard
• increased survival rate (due to aggression & defending), but increased further if food isn’t contested for (X need to divide time between foraging and defending)

Question 11

Black-winged damselfly (Marden & Waage)

Answer 11

• winner determination not weight-related, but % fat (more energy reserves)

Question 12

Speckled wood butterfly - who wins? (Davies)

Answer 12

• “arbitrary rules” in settling contests?
• resident butterfly always wins territory (arbitrary bc unrelated to fitness)
• alternative explanation that contests are settled due to resource-correlated asymmetries in thoracic temperature (not arbitrary)

Question 13

Schjelderup-Ebbe (~1935)

Answer 13

• studied chicken aggressive interactions
• “pecking order” reflects dominance hierarchy found in chicken groups
• unfamiliar hens + fighting over food = usual winner - dominant; usual lose - subordinate
• A > B > C > D etc
• need <10 chickens to remember past interactions

Question 14

Dominance hierarchies

Answer 14

• naturally, established dominance hierarchies are usually “linear” & stable over periods of time
• rare and temporary intransitive hierarchies less common in nature

Question 15

Dominance hierachies in primates controversies

Answer 15

• dominance emphasized in early studies
• does dominance really exist in primates? more complex than chickens & closely related to humans –> more research performed on primates
• is it the key to understanding primate societies?
• how to measure? correlation vs. values?

Question 16

The baby & the bathwater (Bernstein)

Answer 16

• bathwater so dirty, you may lose the last bathed baby in it

Question 17

Assessing dominance in monkeys?

Answer 17

• “grin” (bared teeth expression, typically by adult males but also seen in others)?
• yawning?
• grooming?
• first access to food/water?
• access to mates?
• displacement

Question 18

Intersexual aggression: gulls

Answer 18

• male attack female –> mistaken identity?
• theory: to prove female’s lack of fitness & female X trying to get free meal (from male courting) –> prove female attraction to male

Question 19

Intersexual aggression: praying mantis

Answer 19

• sexual cannibalism due to survival strains (food) –> rare
• also seen in male Montpellier snakes eating females

Question 20

Intersexual aggression: ring doves

Answer 20

• female requires male courtship to come into reproductive condition
• if female already courted by other male, ovulation occurs later (sperm stays in reproductive tract for a minute) –> increases likelihood of parenthood of later male
• male very involved in raising young (costly)
• female may leave to mate with 2nd male –> how to ensure young is yours & limit energy waste?

Question 21

Infanticide

Answer 21

• seen in lions, langurs (& other primates), Belding’s ground squirrel (& other rodents)

Question 22

Hanuman langurs

Answer 22

• 1 male & many females
• male challenged –> will lose to stronger & younger male
• young males often killed by head male
• Sarah Hrdy: males evolved this strategy to protect genetic spread –> only attack nursing young –> received negative reception due to “for the group” popular belief

Question 23

Lions

Answer 23

• females X develop fight back bc X all male cubs will be killed, esp past nursing

Question 24

Evidence supporting the hypothesis that infanticide is adaptive

Answer 24

• most compelling in species (i.e. lion, langurs) in which small groups comprised of many females and 1 breeding male
• male tenure limited - and thus so are mating opportunities
• males X kill own infants
• young nursing infants are killed soon after male takeover
• females resumes cycling & becomes receptive sooner

Question 25

Controversy surrounding the hypothesis that infanticide by males is adaptive

Answer 25

* how widespread? * some claim infanticide in species where social system X fit lions/langurs' pattern

Question 26

Daly & Wilson (1988)

Answer 26

* "children living w/ a stepparent & a genetic parent are 40x more likely to be physically abused" * controversial & extrapolates

Question 27

Belding's ground squirrel

Answer 27

* infanticide committed mostly by adult females that X reside in same area as victim * females X kill relatives & will help kin protect their young from infanticide

Question 28

Storks

Answer 28

* parental killing of young intentionally * eggs hatch asynchronously --> different development stages --> older tend to survive for parents to conserve energy * storks' young may also abuse younger siblings (advantage by already being fed & large) --> parent X feed offspring when pushed out of nest

Question 29

American coots asynchronous hatching

Answer 29

* punish begging-food young by pecking --> concentrate punishment --> chosen 1 stops begging & starves to death * cycle continues so long as there is a surplus of food

Question 30

Siblicide

Answer 30

* seen in numerous birds * to make eggs hatch asychronously

Question 31

Crimson Rosella Parrots

Answer 31

* no fixed rule regarding asynchronously hatching * parents feed evenly & every nestling receives adequate ration * sometimes eldest will share w/ youngest & weakest * after ~3 weeks, strength & weakness differences have evened out --> nestlings about the same size

Question 32

Burrower bug siblicide

Answer 32

* mom stnads over her egg mass & vibrates --> initiate sync * lab setting: eggs hatch asynch w/o vibe --> young cannibalize older siblings just after first molt before exoskeleton hardens

Question 33

Bowl & doily spiders (Austad)

Answer 33

* outcome of aggressive contests depends on female reproductive value & opponent's fight ability * 1st male priority in sperm competition (95% fertilized by 1st male & can fertilize while fighting) * **Sequence: investigation (courtship & pseudocopulation) followed by mating** * avg # eggs fertilized for all females enoucountered by male = avg value of femlae when first encountered = 10 * virgin 4x more valuable * male fighting ability varies w/ body size * **experiment: introduce 2nd male and assess fighting behavior of 1st male at diff points of mating sequence** * when **female reprod. value (V) = for both males** --> fights settled by **male body size** * when **males = size**, fights settled by differences in **V** * when **residents smaller than intruders** --> **persist more in fights w/ strong V** * **--> give up after 7 min copulation** * **most serious fights when V/k (k=cost of fight) identical**

Question 34

Evolutionarily Stable State (ESS)

Answer 34

* models of behavior that take into account that the benefits (& costs) of a behavior can depend upon what other animals in the population are doing * also recognize that, under certain conditions, different behaviors can be of equal value

Question 35

Hawk-Dove Model of Aggression

Answer 35

* "aggressive" vs. "shy" strategies * HvH: 0.5 injury + 0.5 W = -0.25 * HvD = H W * DvH = D L * DvD = display --> attacker wins 0.5 encounters * Avg payoff: H = 7/12; D = 5/12

Question 36

Is ESS optimal?

Answer 36

* no - avg pay-off is 6.25/contest * if "all individuals "agreed" to fight as "doves", avg pay-off would be 15 * but, pop composed only of Ds would be vulnerable to invasion by selfish mutant (H)

Question 37

Female digger wasp nesting strategies

Answer 37

* "diggers" & "enterers" * 100 minutes to dig burrows * females X seem to distinguish empty vs. occupied burrows --> fights * measured success of two strategies based on # of eggs laid/unit time * **to be evolutionarily adaptive --> need both strategies to pay off equally** * **individuals females used both strategies --> facultative use** * is it really adaptive? --> just need more time to see