1
Q
Aggression (Wilson)
A
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?
2
Q
Agonistic
A
refers to any activity related to fighting, whether aggression, concilation, submission, or retreat
3
Q
Self-restraint in aggressive behavior
A
- 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”
4
Q
What regulates aggression?
A
- 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)
5
Q
Costs of aggressive behavior
A
- potential injury
- time & energy
6
Q
Benefits of aggressive behavior
A
- contextually dependent
- increase individual fitness through access to resources/mates
- improved reproductive outcomes
- reduction of competitor’s fitness
7
Q
Aggressive behavior types
A
- interspecific competition over resources
- territorial aggression
- dominance behavior
- sexual aggression (intra- & intersexual)
- infanticide
- parental aggression
- sibling aggression
- predatory/anti-predator aggression
8
Q
interspecific competition over resources
A
hyenas vs. lions over food & beyond
9
Q
Questions concerning territorial aggression
A
- why?
- benefits?
- how big territory?
- year-round vs. seasonal
- time/energy?
- qualities to determine contest winner?
- which sex defends?
10
Q
Yarrow’s spiny lizard
A
- 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)
11
Q
Black-winged damselfly (Marden & Waage)
A
- winner determination not weight-related, but % fat (more energy reserves)
12
Q
Speckled wood butterfly - who wins? (Davies)
A
- “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)
13
Q
Schjelderup-Ebbe (~1935)
A
- 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
14
Q
Dominance hierarchies
A
- naturally, established dominance hierarchies are usually “linear” & stable over periods of time
- rare and temporary intransitive hierarchies less common in nature
15
Q
Dominance hierachies in primates controversies
A
- 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?
16
Q
The baby & the bathwater (Bernstein)
A
- bathwater so dirty, you may lose the last bathed baby in it
17
Q
Assessing dominance in monkeys?
A
- “grin” (bared teeth expression, typically by adult males but also seen in others)?
- yawning?
- grooming?
- first access to food/water?
- access to mates?
- displacement
18
Q
Intersexual aggression: gulls
A
- 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
19
Q
Intersexual aggression: praying mantis
A
- sexual cannibalism due to survival strains (food) –> rare
- also seen in male Montpellier snakes eating females
20
Q
Intersexual aggression: ring doves
A
- 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?
21
Q
Infanticide
A
- seen in lions, langurs (& other primates), Belding’s ground squirrel (& other rodents)
22
Q
Hanuman langurs
A
- 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
23
Q
Lions
A
- females X develop fight back bc X all male cubs will be killed, esp past nursing
24
Q
Evidence supporting the hypothesis that infanticide is adaptive
A
- 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
25
Controversy surrounding the hypothesis that infanticide by males is adaptive
* how widespread?
* some claim infanticide in species where social system X fit lions/langurs' pattern
26
Daly & Wilson (1988)
* "children living w/ a stepparent & a genetic parent are 40x more likely to be physically abused"
* controversial & extrapolates
27
Belding's ground squirrel
* 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
28
Storks
* 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
29
American coots asynchronous hatching
* 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
30
Siblicide
* seen in numerous birds
* to make eggs hatch asychronously
31
Crimson Rosella Parrots
* 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
32
Burrower bug siblicide
* 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
33
Bowl & doily spiders (Austad)
* 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**
34
Evolutionarily Stable State (ESS)
* 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
35
Hawk-Dove Model of Aggression
* "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
36
Is ESS optimal?
* 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)
37
Female digger wasp nesting strategies
* "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
