Bio 281 2011 Lecture 12 - Communication

Communication Communication “Action by one animal that alters the behavior of another animal in a way that is adaptive to one or both participants” Requires some degree of intentionality Signals Signals signal receiver sender discrete signal “categorical” graded signal “continuous” Signal = manifestation of communication Evolved for that function (e.g. not body size) Signals Some signals change the meaning of signals that follow (= metacommunication) 1 Intraspecific communication Position of sun’s azimuth on horizon von Frisch: successful foragers convey vector information to naïve hive mates via waggle dance What provides directional information? The honey bee waggle dance The honey bee waggle dance How do they keep track of distance traveled? Honeybee forager trained on feeder directly toward sun’s azimuth Ability to compensate for sun’s movement requires biological clock! Waggle dance controversy If blinded, forager continues dancing, but artificial “sun” influences interpretation of dance Interspecific communication? California ground squirrel Recruits’ flight time longer than expected Infrared tail stimulus causes snakes to adopt defensive posture Rattlesnakes detect ground squirrels with thermoreceptors Resolution requires quantitative evaluation of bee flight paths…. But is this a signal? 2 Interspecific communication Interspecific communication California ground squirrel Rattlesnakes detect ground squirrels with thermoreceptors Response to gopher snake, which lack thermoreceptors Signal evolution Signal evolution Signal may evolve for one function, then be co-opted for another Signals may evolve to exploit preexisting biases in sensory systems spotted bowerbird Signal evolution Parsimony suggests ancestor was swordless Female maculatus prefer swords! Sceloporus virgatus lack blue ventral patches S. virgatus respond to artificial blue patches Close relatives have them 3 Exploiting a sensory bias Exploiting a sensory bias Population mean frequency of “chucks” = 2.55 kHz Male túngara frogs produce simple (whines) or complex (whines + chucks) calls Best frequency of basilar papilla in ear = 2.13 kHz Preferred by females túngara frog Mike Ryan Similar tuning in ear of coloradorum, which lacks “chuck” Why do females prefer complex songs? Handicap principle Harris’s sparrow Why produce such costly signals? Elk Costly signals are more likely to be honest indicators of quality, therefore should be more salient to conspecifics Amotz Zahavi European toad Honest signaling Number of attacks by intruders Honest signaling European toad High pitch Low pitch Small male defender High pitch low pitch Large male defender 4 Honest signaling Costs of signaling Talk is cheap, at least in birds Honesty enforced by costs 1. Energetic costs 2. Third party interception a. Predators, parasites b. Conspecifics (eavesdropping) 14% raise in metabolic rate in singing canaries Costs of signaling Costs of signaling number of push-ups threat posture duration Energetic costs of display may be greater in lizards baseline endurance reduced endurance Minimal cost of singing in pied flycatchers May be intercepted by unintended receiver Photuris female baseline endurance reduced endurance Threat posture compresses body, increases anaerobic respiration (lactate in blood) Costs of signaling Photinus male Why “femme fatales”? Photinus pattern indicated by “F” Costs of signaling Complex túngara frog calls are attractive to other animals as well… Photinus produce lucibufagins Photuris do not Palatable Photuris female Photinus male with lucibufagins + Unpalatable Photuris female = 5 Costs of signaling Costs of signaling What would you predict about complex calls given by solo males versus males in groups? Positive phonotaxis to chucks by blood-sucking flies Eavesdropping Third party gains information from an interaction that could not be obtained from the signal alone Eavesdropping Betta splendens Latency to approach Latency to display “white” loses “white” wins Winners, losers in “seen” and “unseen” interactions sequentially put into tank with subject male 6