S1). The recordings are also from the population of mammal-eating
killer whales residing in British Columbia, and therefore may differ from those of the whales in the Bahamas. We cannot disregard the possibility that these two alterations may have been significant enough to change the whale’s perception of the stimulus, from that of a predation call to simply a novel signal. Additionally, while the Navy MFA sonar contains frequency and timing elements similar to that of killer whale predation calls, it is not an exact match. In the MFA playback, one 1.3 s MFA sonar sound was played every 25 s, while the killer whale stimulus was an actual recordings of natural sounds, often with more than one vocalization every 25 s. However, both the MFA Sotrastaurin purchase and killer whale sounds are below the best hearing range of those beaked whale species whose hearing has been measured (Cook et al. 2006). The lowered perception of signals in this frequency range may mean that the whales err on the side of caution and interpret the sonar signals in a natural behavioral context as similar to the sounds of a predator. The mismatch of some of the elements of the two signals may mean that the whales require either higher received levels or greater cumulative sound exposure levels in order to induce an antipredator reaction. While it is not possible to draw a direct connection between MFA sonar and an antipredator behavioral reaction in
M. densirostris due to the limited sample size and confounding factors, a definitive behavioral reaction has been quantified in selleck compound this experiment. Despite the confounding factors, our results do show that Blainville’s beaked whales respond to modified killer whale predation sounds with a prolonged
and directed avoidance reaction. The method developed here can be applied to movement data from future controlled exposure experiments. Further experiments should focus on differentiating between the reactions to the two stimuli. The authors acknowledge the support and involvement of numerous field participants in this project. In particular, we acknowledge Leigh Hickmott who provided click here tagging support, and Walter Zimmer for analysis of tag data. In addition, we acknowledge Ian Boyd, Christopher Clark, Diane Claridge, David Moretti, and Brandon Southall for their invaluable work conceiving of, planning, and executing this project. We thank Ari Daniel Shapiro for the initiation of the data analysis. We also thank Volker Deecke for providing the recordings of killer whales used as a playback stimulus. The authors acknowledge the support of the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) in the completion of this study. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. This research was conducted under permits for marine mammal research issued by the U.S.