Auditory temporal summation in pinnipeds.

Abstract

In addition to improving the understanding of auditory processing in pinnipeds, direct measures of temporal summation are relevant to the selection of signal parameters when conducting audiometric research, assessing the effects of signal duration on communication ranges, and evaluating the potential auditory impacts of anthropogenic signals. In the present study, individuals from three pinniped species were tested to determine how signal duration influenced pure‐tone hearing thresholds. The psychophysical method of constant stimuli was used to obtain aerial thresholds for each subject at nine different signal durations ranging from 25 to 500 ms. Parameter estimates derived for a California sea lion (Zalophus californianus) from an exponential model of temporal summation yielded time constants (τ) of 176, 98, and 141 ms at frequencies of 2.5, 5, and 10 kHz, respectively. Preliminary results with a northern elephant seal (Mirounga angustirostris) at 5 kHz (this study), and a harbor seal (Phoca vitulina) at 2.5 kHz [M. M. Holt et al., J. Soc. Am. 116, 2531 (2004)] show similar values for (τ), 134 and 144 ms, respectively. These time constants are similar to those of other mammals tested and do not appear to vary with respect to frequency.