Auditory evoked potentials in two short-finned pilot whales (Globicephala macrorhynchus)

Area of Science:

• Marine Mammal Auditory Science
• Cetacean Bioacoustics
• Veterinary Audiology

Background:

• Short-finned pilot whales (Globicephala macrorhynchus) are toothed whales that rely heavily on hearing for survival.
• Understanding their auditory capabilities is crucial for conservation and welfare, especially in human-managed settings.
• Previous research on pilot whale hearing is limited, necessitating further investigation.

Purpose of the Study:

• To measure the hearing sensitivities of two short-finned pilot whales.
• To compare the auditory evoked potentials of an adult female and a stranded juvenile male.
• To assess the impact of hearing sensitivity on echolocation capabilities.

Main Methods:

• Auditory evoked potentials (AEPs) were measured in response to acoustic stimuli.
• Stimuli included broadband clicks and sinusoidal amplitude modulated (SAM) tones.
• Hearing thresholds were determined across a range of frequencies for both individuals.

Main Results:

• The adult female pilot whale demonstrated auditory thresholds comparable to other odontocetes, with best sensitivity around 40 kHz and an upper hearing limit of 80–100 kHz.
• No click-evoked potentials were detected in the juvenile male.
• Testing with SAM tones revealed severe hearing loss in the juvenile male above 10 kHz.

Conclusions:

• The adult female pilot whale possesses functional hearing within the expected range for echolocating cetaceans.
• The juvenile male exhibits significant hearing impairment, likely affecting its ability to echolocate and navigate.
• These findings highlight the importance of auditory health assessment in stranded or managed marine mammals.