Recent data indicate that odontocete cetaceans, notably beaked whales, exhibit behavioral responses to anthropogenic noise, including Navy sonar (Tyack et al. 2011, McCarthy et al. 2011). A key data gap for conservation and management is to document under what conditions behavioral responses occur, and if these result in biologically significant effects on individuals and/or their populations.
To address this need, the Marine Mammal and Turtle Division of SWFSC is currently undertaking collaborative field efforts to deploy satellite tags (Andrews et al. 2008; Durban and Pitman 2011; Figures 1,2) on whales on and around the operations range at the US Navy’s Atlantic Undersea Test and Evaluation Center (AUTEC; http://www.navsea.navy.mil/nuwc/newport/autec )in the northern Bahamas. This collaboration with the Bahamas Marine Mammal Research Organization (bahamaswhales.org) and the US Naval Undersea Warfare Center (http://www.navsea.navy.mil/nuwc ) aims to monitor the movements and diving behavior of whales relative to Navy exercises involving the use of active sonar.
Figure 1: A satellite LIMPET tag being deployed on the dorsal hump of a sperm whale at AUTEC. These small low-profile tags are attached using a crossbow to project the tag on a projectile bolt; on contact with whale this bolt falls away (as shown), leaving only the transmitter tag attached to the animal (as indicated by the red arrow). Photographs: Bahamas Marine Mammal Research Organisation.
Figure 2: Adult male Blainville’s beaked whale at AUTEC with a satellite LIMPET tag attached at the base of the dorsal fin. Photograph: Bahamas Marine Mammal Research Organisation.
With funding from the US Navy's Environmental Readiness Division, in 2009-2012 small satellite transmitter tags have been deployed on sperm whales, melon-headed whales, short-finned pilot whales and Blainville’s beaked whales – a species that has been shown to be particularly vulnerable to disturbance by sonar – in advance of a Navy exercises. A new complimentary project, with funding from the Strategic Environmental Research and Development Program (SERDP; 2011-2014), is focusing tagging efforts in adjacent areas away from AUTEC in order to provide baseline data on "normal" movement and diving of these species.
The combined data from these efforts will be used to relate changes in movement and diving of odontocete cetaceans to received noise levels to characterize behavioral responses to sonar exposure, and support the development of mitigation strategies.
Results from satellite tag deployments support the interpretation from passive acoustic monitoring (McCarthy et al. 2008) that beaked whales swim several tens of kilometers away from sonar exercises and take several days to return after sonar transmissions cease (Figure 3). Current field efforts are focusing on the deployment of tags that transmit dive depth data to investigate if foraging dives are disrupted during these displacements.
Figure 3 (From Tyack et al. 2011). Locations of a Blainville’s beaked whale satellite tagged before a naval sonar exercise in the AUTEC range in May 2009. For each segment of the track in subplots A-D, the start is plotted with a white square and the end is marked with a red square. The shaded area indicates the extent of the AUTEC range hydrophone array. (A) Locations recorded 72 h before a sonar exercise started on the AUTEC range. (B) Locations recorded during the 72 h sonar exercise. (C) Locations recorded 72 h after the exercise ended. (D) Locations recorded between 72 and 144 h after the exercise ended. (E) Distance from each location to the center of the AUTEC range as a function of date.
Andrews, R., Pitman, R., Ballance, L. 2008 Satellite tracking reveals distinct movement patterns for Type B and Type C killer whales in the southern Ross Sea, Antarctica. Polar Biology. 31, 1461-1468.
Claridge, D.E. and Durban, J. 2009. Abundance and movement patterns of Blainville’s beaked whales at the Atlantic Undersea test and Evaluation Center (AUTEC). ONR Program Review 7-10 December 2009, Alexandria, VA.
Durban, J.W., Pitman, R.L. 2011. Antarctic killer whales make rapid, round-trip movements to subtropical waters: evidence for physiological maintenance migrations? Biology Letters. doi:10.1098 / rsbl.2011.0875.
McCarthy, E., D. Moretti, et al. 2011. Changes in spatial and temporal distribution and vocal behavior of Blainville's beaked whales (Mesoplodon densirostris) during multiship exercises with mid-frequency sonar. Marine Mammal Science 27(3): E206-E226.
Tyack, P. L., Zimmer, W. M. X., Moretti, D., Southall, B. L., Claridge, D. E., Durban, J. W.,Clark, C. W., D'Amico, A., DiMarzio, N., Jarvis, S., et al. 2011 Beaked Whales Respond to Simulated and Actual Navy Sonar. PLoS ONE. 6, e17009.