1 How is communication adaptive?

2 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

3 How is signal-producing adaptive for the sender? SenderReceiver Signal

4 Example: How is a raven’s food call adaptive? H1: Call recruits family members to food H2: Call recruits a coyote to open up the moose carcass H3: Call recruits others to reduce the risk of predation through the dilution effect H4: 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

5 How does natural selection shape the sender’s signals? SenderReceiver Signal Illegitimate Receiver

6 Example: illegitimate receivers have shaped the begging calls of bird nestlings Tree nesting Silent Ground nesting 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

7 Example: illegitimate receivers have shaped the calls of great tits Hypothesis: The tit’s “seet” alarm call has evolved properties Prediction: Unrelated species should

8 Example: illegitimate receivers have shaped the calls of male tungara frogs WhineWhine-chuck Hypothesis: Bats make the whine-chuck call especially costly for males ? Prediction 1: Prediction 2:

9 Are signals honest? SenderReceiver Signal

10 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)

11 How is a receiver’s response to a signal adaptive? SenderReceiver Signal

12 A challenger often gives up after a mere threat How is this adaptive for the winner? How is this adaptive for the loser?

13 Example: Giving up early can be adaptive for the “loser” of antlered flies Hypothesis: antlered flies measure body size to determine Predictions: P1: P2:

14 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:

15 How can deception evolve? SenderReceiver Deceptive Signal Illegitimate Sender Deceptive signal

16 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?

17 What might maintain deception? (or in other words, why do receivers fall for lies?)