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.
reproductive success than other females.
is penis sniffing. Both males and females
is an enlarged clitoris.
selective advantage to balance this.
What is benefit to female?
(1) Natural selection can only operate on
the material available to it.
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
Ear: thin tympanic
an air sac.
Vibration of air sac
noctuids to hear ultrasound?
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 communication
Tungara frogs attract mates by calling. communication
Males give whining call sometimes followed by communication
one or more “chucks.” Females prefer males
who give chucks.
Fig 9.30b communication
If females prefer males who chuck, communication
why don’t all males chuck all the time?
Because bats prey on calling males. communication
Fig 9.30 a
Example 2. communication
Female swordtail fish prefer males
with long tails.
Platyfishes close relatives of swordtails. communication
Males have short tails. Female
Platyfish prefer males with artificially
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 place.
Males compete to control groups, but rarely resort to pushing matches.
Instead, first engage in roaring matches. pushing 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. pushing matches.
Males with smaller antlers usually retreat.
Antler size pushing matches.
with body size
and so it is
Responding to a deceptive signal pushing matches.
Maladaptive mate choice in an Australian beetle pushing matches.
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.
Anglerfish attract pushing matches.
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.