Chapter 9. The evolution of communication. Hyena social behavior. Hyenas live in social groups called clans. Clan members defend a territory and hunt in groups. Females are the dominant members of the clan and have a clear dominance hierarchy. Dominant females have higher
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The evolution of communication.
Dominant females have higher
reproductive success than other females.
Major feature of social interaction in hyenas
is penis sniffing. Both males and females
Female penis really a pseudopenis, which
is an enlarged clitoris.
Enlarged pseudopenis is costly.
selective advantage to balance this.
What is benefit to female?
Things to remember about evolutionary
(1) Natural selection can only operate on
the material available to it.
Panda’s strip bamboo with “thumb.”
Thumb is modified wrist bone (radial
True thumb committed as part of foot.
Natural selection forced to use available
(2) Evolutionary intermediates must be
improvements over what preceded them.
An organism cannot get worse to ultimately
(3) Intermediate structures can have
different functions to their current ones,
but should be useful in some way.
Human ear bones were once jaw bones.
Had to work effectively at both jobs.
banging “castanets” on their wings
together. Sounds are ultrasonic
Ears on side of thorax.
Ear: thin tympanic
an air sac.
Vibration of air sac
What was likely selection pressure on
noctuids to hear ultrasound?
Noctuids evolved hearing to avoid bats.
Later evolved signaling ability.
existing sensory system to develop
evolved from nothing (e.g. Panda’s
precede evolution of many signals.
insects have floral odor (exploits sensory bias towards food finding). Examples:
Example 1: Tungara Frog
Tungara frogs attract mates by calling.
Males give whining call sometimes followed by
one or more “chucks.” Females prefer males
who give chucks.
If females prefer males who chuck,
why don’t all males chuck all the time?
Because bats prey on calling males.
Fig 9.30 a
Female swordtail fish prefer males
with long tails.
Platyfishes close relatives of swordtails.
Males have short tails. Female
Platyfish prefer males with artificially
Elongated tail in swordtails evolved after preference in place.
very similar in sound and hard to locate.
resources? What is the benefit to
giving up a fight?
engaging in fights it probably
expensive and difficult for smaller/weaker individuals to imitate.
Should be good indicators of fighting
Male red deer control groups
Males compete to control groups, but rarely resort to pushing matches.
Instead, first engage in roaring matches.
Roaring is energetically expensive. Only
males in top condition can roar for a long
time. Only if roaring match is indecisive
does escalation to fighting take place.
Antlered flies display antlers to rival males.
Males with smaller antlers usually retreat.
with body size
and so it is
Responding to a deceptive signal
Maladaptive mate choice in an Australian beetle
better by responding to light flashes.
who don’t respond aren’t eaten, but don’t mate either.
spiders by producing prey-like vibration on web.
small fish by waving
a fish-shaped lure.
Benefit of attacking
likely prey outweighs
low risk of predation
for small fish.
mixed-species flocks with other birds.
spot approaching predatory hawks.
it is chasing.
tanager-shrike gets item.