Survival and reproduction

masquerade

blend into surroundings

element imitator

masquerade as something part of the environment, e.g. a stick

object imitator

masquerade as something in addition to environment, e.g. droppings

mimicry

look like another animal

batesian mimicry

harmless spp. mimics harmful spp.

mullerian mimicry

2 harmful spp. mimic each other

aposematic coloration

colored brightly to ward off predators

acoustic aposematism

use noises to warn predators of distastefulness

masquerade effect

predator takes longer to attack prey when it doesn’t know what the prey is mimicking

john skelhorn (2010)

experimented with masquerading with chicks and caterpillars

true/false: coloring is more cryptic when an animal is solitary

true

true/false: coloring is more conspicuous when prey lives in groups

true

primary defense mechanism

avoiding detection via masquerade

secondary defense mechanism

escaping or tasting bad

crypsis

ability to avoid detection by predators

motion dazzle

patterns that interfere with perception of prey’s speed/direction

aperture problem

motion dazzle may result from integration of antagonistic local signals

local brightening

motion moving away from animal

local darkening

motion moving towards animal

looming motion

motion towards/away from animal

descending contralateral movement detectors

bilateral pair of neurons that respond to looming motion and help trigger escape

natural selection

competing successfully for resources, territory, etc. 

sexual selection

competing successfully for mating opportunities

types of sexual selection

intrasexual and intersexual

intrasexual selection

competition within sexes

intersexual selection

competition between sexes

fisher’s runaway hypothesis

the female-preferred trait will become more exaggerated over time, e.g., male tails becoming longer and longer (Andersson 1982)

sexy sons

female preference for trait + male trait = sexy son with trait and daughter with preference for trait

stalk-eyed flies

showed that trait exaggeration and female preference trait are influenced by the same genetic factor (covariance)

true/false: sometimes sexual selection works against natural selection

true; some ‘sexy’ traits make it harder to survive

direct benefits

non-genetic, e.g. male providing food to female in exchange for sex

indirect benefits

genetic, ‘good genes’

zahavi’s handicap principle

costly traits may be a handicap and indicate the quality of the male who has them (indicator mechanism)

qualifying handicap

males survive (good) or die (bad) as a result of the trait

conditional handicap

only the best males develop the trait

revealing handicap

the trait reveals things about the male, like good health

strategic choice handicap

the male advertises his traits at his discretion 

example of handicapped traits

longer tails on swallows are preferred by females and have less mites, BUT make it harder to forage

hamilton-zuk hypothesis

secondary sex characteristics can reflect resistance to disease, e.g., male peacocks with more eyespots have better immune systems

immunocompetence handicap hypothesis

some secondary sex characteristics come at a cost to immune function, e.g., testosterone in males is immunodepressive

anisogamy

gametes are different sizes for males and females

female goal in mating

good male with good resources

male goal in mating

produce as much offspring as possible

EPP

environmental potential for polygamy; extent to which mates can be defended and monopolized

when is EPP high?

when resources (thereby females) are clumped together

polygyny

male mating with multiple females

types of polygyny

resource defence, female defence, lek

resource defence polygyny

males defend resources that females want, e.g. damselflies defending egg laying spots

female defence polygyny

males defend females and create harems, more likely if females are gregarious, e.g. elephant seals

leks

small male display territories, basically dance floors

lek polygyny

males attract females via leks

monogamy pros/cons

enhanced direct fitness for both parents but demands parental care

polyandry

female mates with multiple males, gives her the opportunity to desert

cooperative polyandry

females have multiple male mates and they all raise a single brood together on one territory

why does cooperative polyandry happen?

low number of females in the population