BEHAVIORAL RESPONSES OF MARINE MAMMALS TO SOUND

Many historical methods of studying marine mammal behavior have included surface observations or relatively coarse methods of monitoring individual or group movement patterns. Such approaches may provide glimpses into individual behavior and can allow big picture evaluations of distribution over long time periods. However, many important decisions about whether and how human disturbance from noise in the oceans may affect animals have to be addressed with greater resolution and control to relate a particular kind of sound exposure with a potential response that can be distinguished from naturally variable behavior. 

Through research partnerships on several long-term research projects around the world, we have helped develop new insights into both quantifying marine mammal behavior in fine detail and measuring how different behaviors can be influenced by human sound. These projects have included the careful experimental introduction of sound in areas where high-resolution tag sensors enable us to monitor many kinds of behavior before, during, and after moderate levels of sound are experimentally presented; this enables us to specifically relate reactions with exposure in ways that anecdotal observational studies cannot. A major research effort involving many of our COA colleagues and partnerships has recently been conducted in the Channel Islands off southern California (www.socal-brs.org). A recent paper on our collective progress in these areas lead by COA partners provides a synthesis of our current understanding of these issues. Essentially, some species (such as beaked whales) are generally much more sensitive than most other species, but responses have been measured in most species with their type and severity depending strongly on what animals are doing at the time (behavioral state) and other contextual factors such as proximity and ecological factors.