What do Orca calls mean? Plasticity within vocal repertoire suggests that call structure might vary according to context and/or emotional state Potentially variable parameters: Frequency Amplitude Duration Sequence Tone quality
The Motivation-Structural Rules Hypothesis Eugene Morton (1977) the harshness or tonality of a sound gives insight regarding the caller’s motivational/emotional state Applies to close-contact situations Darwin’s Principle of Antithesis (1872) Evolutionary advantage of unambiguous calls May be possible to discern meaning from killer whale calls by looking at structure of sounds
Harsh, Tonal, and Frequency- Modulated Calls Used in Study S37 (Harsh) S19 (Tonal) V4 (Frequency-Modulated)
Methods Data Sets: Beam Reach 2010 Collected on the Gato Verde during 5 weeks at sea Historical data from Lime Kiln State Park Recordings made by Monika Wieland, Behavioral Data taken by Dr. Robert Otis and students Greeting Ceremony video Six minute recording and corresponding video from 2005
Results Rates of S37, S19, and V4 were much higher in Greeting Ceremony than in other recordings (Wilcoxon Signed Rank Test, p=0.033)
Discussion Best data – greeting ceremony. What does it show? Harsh/tonal/f-mod calls occur at higher rates during intense socializing when motivational states are subtle and when it is important to get messages across without ambiguity. My data/ Monika’s data S19 calls occurred much more than S37 or V4. Both S37 and V4 occurred more often during active states than non-active states, and relationship between harsh/f-mod calls in loose vs close group spread is unclear.
Discussion contd SHOW SPECTROGRAMS HERE!! (maybe gradation from tonal to harsh??)
Conclusions Small sample size Limiting definitions Inconsistent methods BUT, this study has shown that SRKW calls DO lend themselves to being categorized as either tonal or harsh, but also that there is a large degree of plasticity – lots of “in-between” calls Future studies should aim to quantify harshness and tonality. Measuring specific acoustic parameters would make study much stronger. Should also learn more about S10 vs V4 calls.
Acknowledgements I am very grateful to the following people for contributing to the realization of this study: Friday Harbor Labs, University of Washington Dr. Jason Wood Dr. Val Veirs Dr. Scott Veirs Capt. Todd Schuster Ken Balcomb Monika Wieland Dr. Robert Otis Fellow Beam-Reachers!