Far-field auditory evoked potentials in small and large felids

Abstract

The survival of all tigers existing today is seriously threatened, at least partially, as a consequence of the encroachment of civilization. As a prelude to a proposed long-term study intended to determine the impact of urban noise as an extinction pressure for indigenous tiger populations, auditory brainstem responses (ABRs) were recorded from representatives of three of the four surviving tiger substrains, Panthera tigris altacia, Panthera tigris tigris, and Pantera tigris sumatrae, along with an adult male lion (Panthera leo). Standard procedures were employed to record ABRs on location at the Henry Doorly Zoo and response features were measured along with thresholds to tone bursts spanning the empirically determined frequency response range. Threshold estimates were corrected to compensate for background masking noise by applying a correction factor generated by subtracting frequency-threshold estimates derived from gerbil measurements made on location at the zoo from frequency-threshold estimates derived from measurements made under controlled conditions in the lab from the same animal. While overall response features and input–output characteristics were similar to those observed in domestic cats and other mammals, large felids responded preferentially to very low-frequency tone bursts and poorly to high-frequency tone bursts when compared with small fields.