Animal Behavior Exam 3

pre-existing trait hypothesis

signaler possesses a trait that already conveys informative cues to receiver; trait is then modified and extended through signal ritualization

features of ritualized signals

redundancy

• repetition

• multiple signals with the same meaning

conspicuousness

• opposite meanings are often dramatically different and exaggerated

stereotype

• distinctive form

alerting component

• attention-getting portion at the beginning

sources of ritualized signals

• intentional movements

• motivational conflict

• autonomic response

intentional movements

(sources of ritualized signals)

ex: bird crouching before taking off

• when a bird sees another bird leaving, they pay attention to see why

• indicate what the animal will do, predicting power

motivational conflict

(sources of ritualized signals)

• alternating between different behaviors (ex: zig-zag stickleback display)

• ambivalent behaviors (threat displays combine aggression and fear)

• displacement activities (preening, turf pulling in seagulls, hair twirling during exams, etc)

autonomic responses

(sources of ritualized signals)

ex: piloerection of hair, baboon faces that flush red (or human), canine urination, sweating, etc.

reproduction

finding mates, producing gametes, caring for young

• direct fitness - offspring you produce

• indirect fitness - offspring of close relatives

selection favors traits that enhance reproduction, even if they shorten lifespans

ex: Adactylidium mite feeding on a thrip egg

• females produce 5-8 female offspring and one male

• male mates with all the daughters inside the female’s uterus

• females eat their way out of their mother and kill her after she’s lived about 4 days

Charles Darwin The Descent of Man and Selection in Relation to Sex, 1871

any trait can persist if it aids in reproduction

• ex: peacock feather display; elaborate costly traits exhibited by male birds

can you have more than 2 sexes?

• slime molds and mushrooms have 9-13,000 separate mating types

• male, hermaphroditic, and female individuals (ex: nematodes, gastrotrichs, etc)

• sex-role reversal for each sex and changing sexes (sequential hermaphroditism)

• ex: white-throated sparrows

gender

the suite of behaviors typically associated with one biological sex

white-throated sparrows’ sexes

either 2 sexes, 4 sexes, or 2 sexes and 4 genders

• white-striped morph = promiscuous, poor parental care, aggressive (territorial), tuneful (traits associated with males, but females do it too)

• tan-striped morph = monogamous, good parental care, protective, poor at singing (traits associated with females, but males do it too)

why?

• inversion mutation occurs in 1/3 of birds (paracentric inversion of genes in chromosome)

  • white-stripe = heterozygous for mutation (1/2)

  • supergene

• for reproduction, everyone wants to pair with tan stripes, because they’re good parents (associative mating - opposites pair with each other)

Mixed Evolutionary Stable Strategy (Mixed ESS)

• fertilization specialists (male, sperm) have a higher number of fertilizations, and higher survival rate, when small

• provisioning specialists (female, egg) have a higher number of fertilizations, and higher survival rate, when large

• opposite of bell curve - mid-sized are losers

hypotheses for the evolution of anisogamy

• parasitic gene hypothesis

• battle for the cytoplasmic genome hypothesis

• the cooperative explanation for anisogamy

parasitic gamete hypothesis