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How is communication adaptive?

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6/4/08: Animal Communication: Adaptationist perspective of communication

Lecture objectives:

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)

Signal

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How is signal-producing adaptive for the sender?

Sender ReceiverSignal

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Example: How is a raven’s food call adaptive?

H1: Call recruits family members to foodH2: Call recruits a coyote to open up the moose carcassH3: Call recruits others to reduce the risk of predation through the dilution effectH4: Call recruits other ravens so that all can overwhelm territory owners

Obs1: Call at open carcassesObs2: Call when lots of ravens are already thereObs3: Birds at kill are unrelatedObs4: Pairs at kill were usually quiet

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How does natural selection shape the sender’s signals?

Sender ReceiverSignal

Illegitimate Receiver

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Example: illegitimate receivers have shaped the begging calls of bird nestlings

Tre

e ne

stin

g

Sile

nt

Gro

und

nest

ing

Hypothesis: The higher frequency calls of ground-nesting birds

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 ReceiverSignal

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What might maintain honesty?(or in other words, why not cheat?)

Cheating might hurt

Selection should favor

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 ReceiverSignal

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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

Hypothesis: males can judge the size of a rival by his croak

Observation: Body size influences the pitch of a male’s croak

Prediction:

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How can deception evolve?

Sender ReceiverDeceptive Signal

Illegitimate Sender

Deceptive signal

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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?)