Tagged fin whale call production, associated behavior, and response to anthropogenic sound in the Southern California Bight
Stimpert, A, S DeRuiter, E Falcone, J Joseph, A Douglas, D Moretti, A Friedlaender, J Calambokidis, G Gailey, P Tyack, B Southall, and J Goldbogen. 2015. Tagged fin whale call production, associated behavior, and response to anthropogenic sound in the Southern California Bight. Abstract (Proceedings) 21st Biennial Conference on the Biology of Marine Mammals, San Francisco, California, December 14-18, 2015.
For marine animals, acoustic communication is critical for many life functions, yet individual calling behavior is poorly understood for most large whale species. Until recently, identifying the calling individual in a group of socializing baleen whales, through either passive acoustic monitoring or acoustic tagging methods, has been challenging because of inadequate spatial resolution in localization, and ambiguities in sound measurements recorded from animal-borne tags. A new technique uses accelerometer signals from tags with sufficiently high sensor sampling rate in conjunction with recorded acoustic signals in order to identify calling individuals. We applied this technique to data from 18 fin whales tagged as part of the Southern California Behavioral Response Study (SOCAL BRS). Four of these whales were confirmed to be calling based on this integrated accelerometer and acoustic method, and we were then able to measure body orientation, dive behavior, and surface social behavior in relation to call production. Behavioral metrics associated with elevated call rates included shallow maximum dive depths (10-15 m), little body movement (Overall Dynamic Body Acceleration ~ 0 m/sec/sec), and negative pitch in body orientation (approximately -30 degrees pitch). Whales were also more likely to be traveling than milling, and in groups rather than solitary. These are the first descriptions of body orientation and dive depths at which fin whales are most likely to call, and some possible sound propagation and/or anatomical reasons for these results are considered. We also describe calling responses (or lack thereof) from those animals exposed to simulated mid-frequency active sonar. The call behavior characterizations presented here will help with predicting calling behavior from surface behavior and informing interpretation of passive acoustic data, as well as with further investigating effects of anthropogenic sound on fin whales.