Unformatted text preview: Updates FINAL REVIEW PAPER DUE 4/29! 2PART BIRD COMMUNICATION LAB DUE TUES AFTER BREAK, BY 5 pm Spectrogram Acoustic Analysis Intro, Methods, Results, Discussion for Playback Expt INDEPENDENT PROJECTS BEGIN WEEK AFTER SPRING BREAK Ch. 12 Communication Exchange of signal between sender and receiver to benefit of both... Types of information conveyed comparison with humans Developmental perspective Problems in communication: How do honest signals evolve? (Searcy & Nowicki Reading) Coordinating activity of large groups Mysterious modalities... Auditory Visual Tactile Chemical Modes of Communication: Evolution of Signals Signals are constrained Vocalizations influenced by morphology and behavior: Aggressive vs. Defensive: MotivationalStructural Rules in Vocal Communication
Call frequency indicated by height of line Call structure indicated by thickness of line MotivationalStructural Rules in Vocal Communication
Submission indicated by high frequency, tonal sound Hostility indicated by low frequency, harsh sound Signals grade into each other Referential Communication in Vervet monkeys Cheney & Seyfarth 1984 Wild vervet monkeys in Kenya Vervets have three main threats: Eagles Leopards Snakes Need to respond differently to each of these threats in order to survive Vervet referential alarm calls
8000 6000 4000 2000 0 0 Time (s) 1.25587
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1.1104 2000 0 0 Time (s) 0.331429 0 0 Time (s) 0.219728 Traditional view signaler and receiver both benefit through communication Is Communication Always Honest? But what if an outcome that is good for the signaler is not also good for the receiver?
Is he telling the truth? Is Communication Always Honest? I'm the most fit male around Evolution of Honest Signals To avoid problem of cheating, need signals that accurately reflect an individual's fitness Examples? Signals that depend on physiological attribute like size or age Signals that are costly to produce If signals have costs, then signalers will produce signals that reliably communicate quality Examples? Signals that depend on physiological attribute like size or age Signals that are costly to produce Honest Signals in Amphibians Ex: mating calls in frogs and toads larger toads have larger larynx and are able to produce deeper sounds Costly Signaling in Birds Bird song costs related to not only production, but also to acquisition In temperate songbirds males are main song producers Achieving adult song repertoire requires innate components and learning from conspecifics Seasonal onset of song influenced by hormones and changes in day length Development of Song Innate component Nestlings respond differently to conspecific vs. heterospecific songs Sensitive period for learning Preferentially learn conspecific songs if exposed to variety of possible models Need to receive feedback from their own calls Learned components of Bird Song: Specialized vocal areas in brain dedicated to song learning, perception and production Contain song-selective neurons- respond better to birds own song Also auditory areas in brain with neurons that respond more robustly to conspecific song Song Learning Centers in Brain Learned components of Bird Song: Geographicallyrestricted dialects acquire song similar to conspecifics in same area Some species are openlearners (e.g. canaries, starlings) can learn new songs throughout life often triggered seasonally Neurogenesis in adults New neurons in forebrain corresponding with changes in song production Flexibility in Song Production Influence of Testosterone increase in late Spring corresponding with onset of song Exposing males to T can speed up onset and increase intensity of songs Flexibility in Song Production Seasonal changes in volume of HVC reflects increases in neurons in HVC in Spring Adults have repertoire of 515 songs (established by 1 yr of age) Quality and pattern of notes in song are individuallyspecific Different songs types are not contextspecific (differing from chickadee) So what is purpose of having varied songs? Song Production in male Song Sparrows Song Production in Sparrows Intersexual selection females prefer males with larger song repertoire Why??? - Larger song repertoire correlated with: -Greater offspring survival -Larger HVC volume (reflects costly neural machinery, early environ.) -Higher Testosterone levels ...
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- Spring '11
- Sexual Selection, honest signals, Vervet Monkey, Animal Communication, Song Sparrows