Transcript Communication II

How is communication adaptive?
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6/4/08: Animal Communication:
Adaptationist perspective of communication
Lecture objectives:
Signal
1. Be able to tell if a signal is adaptive,
honest, or deceptive
2. Generate hypotheses and
predictions about the relationship
between components of a signaling
system (sender, receiver, illegitimate
sender, illegitimate receiver)
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How is signal-producing adaptive for the sender?
Sender
Signal
Receiver
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Example: How is a raven’s food call adaptive?
H1:
H2:
H3:
H4:
Call recruits family members to food
Call recruits a coyote to open up the moose carcass
Call recruits others to reduce the risk of predation through the dilution effect
Call recruits other ravens so that all can overwhelm territory owners
Obs1: Call at open carcasses
Obs2: Call when lots of ravens are
already there
Obs3: Birds at kill are unrelated
Obs4: Pairs at kill were usually quiet
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How does natural selection shape the sender’s signals?
Sender
Signal
Receiver
Illegitimate
Receiver
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Ground nesting
Tree nesting
Hypothesis: The higher frequency calls of
ground-nesting birds
Silent
Example: illegitimate receivers have shaped
the begging calls of bird nestlings
Prediction: Ground nests with ground nest begging calls will have
_____________ than ground nests with tree nest begging calls
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Example: illegitimate receivers have shaped
the calls of great tits
Hypothesis: The tit’s “seet” alarm call
has evolved properties
Prediction: Unrelated species should
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Example: illegitimate receivers have shaped
the calls of male tungara frogs
Whine
Whine-chuck
?
Hypothesis: Bats make the whine-chuck call especially costly for males
Prediction 1:
Prediction 2:
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Are signals honest?
Sender
Signal
Receiver
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What might maintain honesty?
(or in other words, why not cheat?)
Selection should favor
Cheating might hurt
There is a
(handicap principle – reliable signals
should be costly to produce)
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How is a receiver’s response to a signal adaptive?
Sender
Signal
Receiver
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A challenger often gives up after a mere threat
How is this adaptive for the winner?
How is this adaptive for the loser?
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Example: Giving up early can be adaptive for the
“loser” of antlered flies
Hypothesis: antlered flies measure
body size to determine
Predictions:
P1:
P2:
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Example: Giving up early can be adaptive for the
“loser” of male European toads
Observation: Body size influences
the pitch of a male’s croak
Hypothesis: males can judge the
size of a rival by his croak
Prediction:
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How can deception evolve?
Sender
Deceptive
Signal
Receiver
Illegitimate
Sender
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Example: female Photirus fireflies deceive
male Photinus fireflies
Who is the sender?
What is the signal?
Who is the receiver?
Who is the illegitimate sender?
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What might maintain deception?
(or in other words, why do receivers fall for lies?)
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