Preliminary investigation of sound reception in southern sea otters (Enhydra lutris nereis).

Abstract

Due to their dependence upon a highly restricted coastal habitat, sea otters are vulnerable to a variety of environmental and anthropogenic threats. Among these is the potential disturbance from human‐generated sources of noise. Presently, there are no data on the auditory sensitivity of sea otters, and little evidence to suggest what sounds may be most relevant to these animals. As an initial step toward describing the acoustic sense of sea otters, we conducted a controlled exposure experiment, adapted from sound exposure studies used in behavioral field research, to efficiently measure the aerial frequency range of hearing in four captive sea otters. This approach was designed to determine which frequencies were audible to each animal, rather than to provide direct measures of auditory sensitivity. The maximum range of aerial hearing determined using this method was 0.125 to 32 kHz. These are the first direct measurements of hearing obtained for sea otters, and the results are relevant to improving understanding of their acoustic communication, evolutionary biology, and behavioral ecology, as well as in supporting ongoing conservation efforts. This research effort draws from the work of Kastak and Schusterman, especially with respect to the value of behavioral baselines in captive studies of marine mammals.