Hearing threshold measurements using auditory evoked potentials of four stranded short-finned pilot whales (Globicephala macrorhynchus) in Key Largo, FL

Abstract

Approximately 26 short-finned pilot whales, Globicephala macrorhynchus, stranded in Cudjoe Key, FL, on May 5, 2011. Four animals, two adult and two juvenile females, were transported to a rehabilitation facility in Tarpon Basin, FL. Auditory evoked potentials (AEPs) were recorded in response to amplitude modulated tone pips modulated at 1000 Hz. AEP thresholds were determined at 10, 20, 40, 80, and 120 kHz for all the four animals. Audiograms were similar to previous findings in pilot whale hearing tests. Short-finned pilot whales have a lower peak sensitivity than other odontocetes such as bottlenose dolphins. Greatest sensitivity was 40 kHz for all whales, while thresholds for the two adults were 25–61 dB higher at 80 kHz than those for the juveniles tested. Click evoked potentials were similar between the four whales and comparable to other echolocating odontocetes. Five total pilot whales have been tested during two separate stranding events; the previously tested juvenile male was found to have profound hearing loss (Mann et al., 2010; Schlundt et al., 2011). These findings add to the limited database of pilot whale (short- and long-finned) hearing studies, of which there are only two others (Schlundt et al., 2011; Pacini et al., 2010).