s. Several species of pinnipeds, including harbor seals and elephant seals, have been directly studied. Recent studies of harbor seals conducted in a pool specially designed for hearing studies (located in the Netherlands) have allowed scientists to more accurately measure hearing sensitivities. Because of the very low background noise, they discovered the lowest hearing sensitivity yet measured in harbor seals.
Studies on other marine species are just beginning to be conducted. A recent study using auditory evoked potential (AEP) techniques with sedated polar bears shows that they have good in-air hearing over a wide frequency range. They hear best between 11.2 kHz and 22.5 kHzNachtigall, P. E., Supin, A. Y., Amundin, M., Roken, B., Moller, T., Mooney, T. A., … Yuen, M. (2007). Polar bear Ursus maritimus hearing measured with auditory evoked potentials. Journal of Experimental Biology, 210(7), 1116–1122. https://doi.org/10.1242/jeb.02734.
Most data regarding sea turtle, shark, and skate hearing come from studies using auditory brainstem responses (ABRs). From this work, scientists know that sea turtles can hear low to mid-frequency sounds underwater, but with poorer sensitivity than mammals.
Sea turtles, in general, hear best between 200 and 750 Hz and do not respond well to sounds above 1,000 Hz (1 kHz). The graph shows that younger sea turtles of any species hear higher frequencies better than older turtles of the same species. As turtles grow older and larger, their hearing sensitivity shifts to lower frequencies.To determine the hearing capabilities in an adult green sea turtle, researchers obtained a behavioral audiogram for an older female green sea turtle, “Myrtle”, housed in the New England Aquarium’s Giant Tank exhibit. Based on her responses, it was concluded adult green sea turtles hear best between 200 Hz and 500 Hz.
Elasmobranchs, including sharks, skates, and rays, appear to respond best to low frequency sounds. The hearing of the little skate was tested using both behavioral and auditory brainstem response methods between 100 and 800 Hz. They were found to hear best at 200-300 Hz. Other species studied with ABRs show similar low-frequency sensitivity.
Additional Links on DOSITS
- Hearing Sensitivity Studies
- How does sound in air differ from sound in water?
- How is hearing measured?
- Sound Production
- Sound Reception
- What sounds can we hear?
Cited References [ + ]
|1.||↑||Nachtigall, P. E., Supin, A. Y., Amundin, M., Roken, B., Moller, T., Mooney, T. A., … Yuen, M. (2007). Polar bear Ursus maritimus hearing measured with auditory evoked potentials. Journal of Experimental Biology, 210(7), 1116–1122. https://doi.org/10.1242/jeb.02734|