Marine Mammals



Mark Baumgartner, Hal Caswell, Mark Hahn, Darlene Ketten, Michael Moore, T. Aran Mooney, Peter Tyack, John Stegeman

Study of Marine Mammal Auditory Systems

In Darlene Ketten's laboratory, studies are directed at understanding how the ears of marine animals, particularly whales and dolphins, are able to hear and use underwater sounds. Biomedical (CT and MRI) micro-imaging techniques are used to study auditory systems from a wide range of species and to produce mathematical and three-dimensional computer models of marine ears. The models allow us to estimate hearing abilities for rare and endangered species, like blue whales, that cannot be tested by normal methods. We also use computer simulations to determine how whale ears withstand rapid pressure changes during dives and how underwater noise affects hearing. Because of the close relationship between what an animal hears and the sounds it produces, work in this laboratory is linked closely with vocalization and behavioral research in the Tyack laboratory. Studies on stranded animals are tied also to research in Michael Moore's laboratory on the effects of pollutants and disease.

Acoustics and Behavior

Studies are conducted on acoustic behavior of a wide variety of species using hydrophone arrays and database organization of sound patterns. Surface and underwater activities of open ocean species, such as fin whales and sperm whales, are investigated with telemetry to follow details of dive profiles relative to water temperature, bottom topography and other environmental factors.

The WHOI cetacean group is determining how marine mammals learn and build individual vocalization patterns and is detailing the social behavior of these highly mobile, migratory animals. They also examine cetacean phylogeny, stock structure, and familial and kin relationships using population genetics methods.

One of the ongoing projects in the Tyack lab is the study of the foraging and acoustic behavior of wild bottlenose dolphins. Detailed feeding behaviors have been observed with an overhead video system, and acoustic activity has been recorded with this system as well as a non-invasively attached digital archival recording tag.

Pollution Effects

In the laboratory of Mark Hahn, the impact of chemical pollutants on marine mammals is being investigated through comparative studies on the biochemistry and molecular biology of the receptors and enzymes involved in toxic chemical action.

Population Dynamics

Quantifying the population dynamics of marine mammals is difficult because of the difficulty of collecting data on individual survival and fertility. In some cases, however, sufficient data have been obtained to permit the development of population models. Current studies on marine mammals by Hal Caswell include the development of stage-classified demographic models from photographic catalog data, assessment of the consequences of bycatch mortality in harbor porpoise, and general investigations of the use of population models in conservation biology.