Basic Hearing and Echolocation Mechanisms of Marine Mammals: Measured Auditory Evoked Potential and Behavioral Experiments FY 2007
Abstract
Marine Mammal sensory systems have evolved to effectively use acoustic energy in the oceans. My objectives are to develop a basic understanding of hearing and echolocation so that knowledge can then be applied to the solution of practical problems as they arise. The most basic hearing measurement is the audiogram which is a series of thresholds across frequencies. Of the 85 species of cetaceans we now have audiograms on 14 species. Audiograms on additional cetacean, and other marine mammal, species may be obtained from stranded animals, from animals in captive display situations, and from catch and release scenarios. We intend to obtain as many valid audiograms as possible as we seek new opportunities in new situations. Other hearing measures such as directionality of hearing are also very important and little is known on most marine mammals. These measures will also be obtained whenever possible. Most of our initial audiometric work measured hearing using behavioral responses (Nachtigall et al, 2000). Measures of auditory evoked potentials (AEP) produce the benefit of being obtained rapidly without requiring captivity or lengthy training. Our recent work (Yuen et al, 2005) shows that the two procedures, while not producing exactly the same results, are certainly comparable. So, we intend to continue using AEP measures to measure the hearing of new species and to continue to measure hearing in other situations. Our initial work on temporary threshold shifts (Nachtigall et al 2003, 2004) with exposures up to 50 minutes combined with shorter term exposures led to an equal energy hypothesis in which it was assumed that the amount of TTS was dependent on the amount of energy received relatively independent of the time of exposure. An objective of our recent work (Mooney et al, 2006) has been to examine whether the equal energy hypothesis is valid for short exposure times.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2007
- Accession Number
- ADA506736
Entities
People
- Paul E. Nachtigall