Signal Costs and Constraints
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Transcript of Signal Costs and Constraints
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
Decision threshold
Four possibilities: hit or correct detection, false alarm, miss, and correct rejection
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.
ROC curves
Signal detection and mate choice
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
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.
Guppy coloration and predation
Frog mating calls attract bats
Male crickets attract females and parasitic Ormia ochracea flies
Female fly ears are tuned to hear male cricket calls
Female red-winged blackbird calls attract predators and defense
Sage grouse displays are costly
Singing consumes energy
Gray treefrogs Carolina wrens
Time lost: lekking antelope males don’t
feed
Conflict with original function
Elongated tails create drag during turns
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
Sender constraints
Body size constrains frequencyLeptodactyline frogs Birds
Constraints on sender learning: HVC and repertoire size
Receiver costs
• Vulnerability to predation while inspecting or comparing signals
• Time lost
• Susceptibility to exploitation, i.e. code-breakers
Code-breaking rove beetle
Receiver constraints
Phylogeny, memory
Visual resolution and body size
Hippocampus size and caching
Memory differs in food storing corvids
Memory differences are task dependent
Hippocampus shows experential changes
Transmission constraints
Tactile communication