Hearing is important to marine mammals for communication, avoiding predators, and finding food. Concern exists over the potential for human-made (anthropogenic) noise in the oceans to affect marine mammals, either by altering their behavior after hearing a sound or by directly affecting their hearing. Unfortunately, little is known about the hearing of most marine mammals even though knowing the range of frequencies an animal hears and the sensitivity to those frequencies are the most fundamental pieces of information necessary to begin assessing the potential impact of human-made sound on marine mammals.
Hearing can be tested in marine mammals by behavioral methods or by measuring brain waves produced in response to the hearing of a sound, which is called an auditory evoked potential (AEP). Behavioral methods are the accepted standard for hearing tests, but AEP methods allow hearing tests to be conducted much more rapidly and in wild animals. The NMMF collaborates with the U.S. Navy Marine Mammal Program in the study of marine mammal hearing using both methods, as well as in the development of tools used for assessing hearing in marine mammals.
Current Research
Scientists within the Biologic and Bioacoustic Research program respond to toothed whale stranding events and to animals under rehabilitation. They currently hold an annual training event for members of stranding networks that have been provided with the technology to perform AEP hearing tests. The NMMF partnered with NOAA Fisheries to develop a national Cetacean Evoked Potential Audiogram Database (CEPAD). The database serves as a central repository for hearing information obtained from whales by the NMMF, other academic researchers, and stranding networks.
