A comparison of behavioral and auditory brainstem response methods for examining hearing sensitivities in the harbor seal (Phoca vitulina)

Auditory brainstem response (ABR) and behavioral methods (method of constant limits and staircase method) were used to generate in-air audiograms for an adult female harbor seal to examine relative sensitivities obtained using the two methods. Behavioral thresholds ranged from 0.250–30 kHz and indicated best sensitivity from 6–12 kHz (∼12 dB re: 20 μPa). The staircase method was more sensitive than the method of constant limits, resulting in thresholds averaging 10 dB lower. ABR thresholds were recorded at 2, 4, 8, 16, and 22 kHz and showed a similar range of best sensitivity (8–16 kHz). ABR and behavioral thresholds differed by an average of 5 dB; ABR thresholds averaged 3.8 dB higher than behavioral thresholds from 2–8 kHz, but were 12 and 3 dB lower at 16 and 22 kHz, respectively. The lower ABR thresholds at higher frequencies may reflect the behavior of the seal during ABR testing as well as broadband characteristics of ABR test stimuli. These results agree with comparisons of ABR and behavioral methods performed in other recent studies and indicate that auditory evoked potential methods represent an accurate alternative to behavioral methods for estimating hearing range and sensitivity in wild animals. [Work supported by NASA: NAS1-20101.]