Download - Signal Costs and Constraints
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Signal Costs and Constraints
• Signal detection theory (pp. 429-438)
• Costs to senders of signaling
• Constraints on senders
• Costs to receivers
• Constraints on receivers
• Transmission constraints
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Decision threshold
Four possibilities: hit or correct detection, false alarm, miss, and correct rejection
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Signal detection theory
ROC = receiver operatingcharacteristic: plots correctdetection against false alarms.As the threshold criterion movesleft to right, the PCD vs PFA
moves down to the left.
Greater separation betweensignal and noise increases d.
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ROC curves
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Signal detection and mate choice
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Implications• Communication is never perfect• Can improve communication
– if senders create more distinctive signals– if receivers acquire greater discrimination ability
• Which of these will happen depends on the relative costs to sender and receiver as well as constraints on signal production or reception
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Sender Costs
• Conspicuousness to predators and parasites– Visual, auditory, or olfactory signals
• Energetic costs of signaling
• Lost time
• Conflict with original function
See Kotiaho, J.S. 2001 Costs of sexual traits: a mismatch betweentheoretical considerations and empirical evidence. Biol. Rev. 76:365-376.
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Guppy coloration and predation
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Frog mating calls attract bats
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Male crickets attract females and parasitic Ormia ochracea flies
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Female fly ears are tuned to hear male cricket calls
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Female red-winged blackbird calls attract predators and defense
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Sage grouse displays are costly
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Singing consumes energy
Gray treefrogs Carolina wrens
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Time lost: lekking antelope males don’t
feed
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Conflict with original function
Elongated tails create drag during turns
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Constraints
• Phylogenetic– Implies insufficient time or genetic variation
for evolution to modify trait
• Physical– Production of signal is impossible given the
organism’s morphology and physiology
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Sender constraints
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Body size constrains frequencyLeptodactyline frogs Birds
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Constraints on sender learning: HVC and repertoire size
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Receiver costs
• Vulnerability to predation while inspecting or comparing signals
• Time lost
• Susceptibility to exploitation, i.e. code-breakers
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Code-breaking rove beetle
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Receiver constraints
Phylogeny, memory
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Visual resolution and body size
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Hippocampus size and caching
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Memory differs in food storing corvids
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Memory differences are task dependent
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Hippocampus shows experential changes
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Transmission constraints
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Tactile communication