Comparison of three Stenella spp. audiograms measured using auditory evoked potentials and behavioral methods

Abstract

The oceanic dolphin genus Stenella is underrepresented in cetacean hearing data. In this study the hearing of three Stenella spp. dolphins was measured using auditory evoked potential (AEP) methods. A single male juvenile Atlantic spotted dolphin (Stenella frontalis) was rehabilitated in Key Largo, Florida, after being sighted alone and emaciated. The Atlantic spotted dolphin’s greatest sensitivity was at 40 kHz, with functional hearing up to 128 kHz. A female spinner dolphin (Stenella longirostris), housed at Mote Marine Laboratory, had peak sensitivity at 40 kHz and functional hearing up to 120 kHz, the highest frequency tested. The sensitive high frequency hearing of the spinner and Atlantic spotted dolphin is similar to that found in other oceanic odontocetes. A pantropical spotted dolphin (Stenella attenuata) was housed at Mote Marine Laboratory and hearing thresholds were determined using AEP and behavioral methods. The pantropical spotted dolphin had a peak sensitivity at 10 kHz, with a cutoff frequency between 14 and 20 kHz. The source of the dramatic high-frequency hearing loss is not known; possible causes include congenital hearing loss (present at birth) or hair cell death due to treatment with ototoxic drugs during rehabilitation.