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Polar Bear Audiometry – Towards Science-Based Exposure Guidelines

HSWRI Program Leader/Project Leader: Ann E. Bowles

Goal

To develop techniques for studying the hearing of large carnivorous mammals and apply the results to problems of conservation and management.

Importance

Since its inception, the Bioacoustics Laboratory has conducted research on marine mammal hearing and applied it to problems like preventing noise impacts, preventing or mitigating fishery interactions, and conserving species at risk.  This project has provided the first behavioral hearing data on a large carnivorous mammal, the polar bear.

Background

City-dwelling humans live in an environment glutted with noise, and tend to ignore sound or treat it as an irritant.  However, for animals sound is an essential modality for navigation, foraging, socializing, caring for young, and for mounting both active and passive defense.  As an example, the polar bear lives in an environment that is very dark a lot of the year and often very quiet.  To understand their interactions with their environment, we must understand what they can hear through testing rather than making assumptions based on what is known for other carnivores.

Methods and Results

The gold standard for hearing studies is based on behavioral responses collected from conscious and cooperative subjects.  There are faster electrophysiological techniques pioneered for studying hearing of unresponsive humans, like babies, and these have been applied to animals, but these must be perfected with reference to behavioral studies.  Thus, accessible individuals in zoological collections are essential to obtaining high-quality data on hearing in healthy individuals, particularly over long periods.

The Bioacoustics Laboratory has conducted research on hearing since the 1970s.  In collaboration with SeaWorld, our staff have produced firsts in the behavioral study of hearing in the beluga, killer whale, false killer whale, short-finned pilot whale, and the polar bear.

Early on, work emphasized the basic biology of hearing.  However, the lab’s staff, collaborators, and students quickly began to focus on practical applications of which the polar bear hearing study is a good example.   We collaborated with the San Diego Zoo’s Institute for Conservation Research (SDZICR) to collect behavioral hearing data from five polar bears at the two facilities.  We found that their hearing range is consistent with estimates made from anatomical data, but not very similar to that of smaller carnivores like dogs and cats at high frequencies.  However, they are at least as sensitive as a dog at low frequencies.

Why Does the Research Matter? Although zoological organizations have cared for a wide range of exotic species from both terrestrial and marine environments for many years, and although access to animals is an essential basis for research on their sensory systems, surprisingly little work has been conducted in this important topic area.  As global climate changes affect marine mammal distribution, and human activities near and in the ocean continue to expand, the work we are doing will inform guidelines under development to protect marine mammals from exposure to noise.

Funding and Donation Opportunities:

  • Hardware and software upgrades: $50,000

Currently, some of the best research on marine mammal hearing is taking place at strandings and other field sites.  The lab is looking for funds to support work on hearing of stranded marine mammals in collaboration with SeaWorld and the HSWRI laboratory in Melbourne Beach:

  • Bioacoustics Postdoctoral Research Associate to assist with development of innovative approaches to data collection and analysis: $100,000
  • Intern stipends:  $2000/stipend x 2 stipends/year = $4000

Fig1_ Owen&Bowles_2011_PolarBearHearing

Selected Recent Publications

Owen, M.A., and A.E. Bowles. 2011.  Auditory Psychophysics and the Management of a Threatened Large Carnivore, the Polar Bear (Ursusmaritimus). International Journal of Comparative Psychology 24: 244-254.

Schlundt, C.E., R.L. Dear, D.S. Houser, A.E. Bowles, T. Reidarson, J.J. Finneran. Auditory evoked potentials in two short-finned pilot whales (Globicephalamacrorhynchus). 2011.  Journal of the Acoustical Society of America 129(2): 1111-1116.

Wolski, L., R. Anderson, A.E. Bowles, and P.K. Yochem.  2003.  Measuring hearing in the harbor seal (Phocavitulina): comparison of behavioral and auditory brainstem response techniques.  Journal of the Acoustical Society of America 113(1):629–637.

 

Selected Historical Publications

Francis, R.C., F.T. Awbrey, C. Goudy, M.A. Hall, D.M. King, H. Medina, K.S. Norris, M.K. Orbach, R. Payne and E. Pikitch. 1992. Dolphins and the Tuna Industry.  National Academy Press, Washington, DC.

Thomas, J.A., R.A. Kastelein and F.T. Awbrey. 1990. Behavior and blood catecholamines of captive belugas during playbacks of noise from an oil drilling platform. Zoo Biology 9:393-402.

Evans, W.E., F.T. Awbrey and H. Hackbarth. 1988.  High frequency pulses produced by free-ranging Commerson’s dolphin (Cephalorhynchuscommersonii) compared to those of phocoenids. Pages 173-181 in R. L. Brownell and G. P. Donovan, eds. Reports of the International Whaling Commission (Special Issue 9).Biology of the genus Cephalorhynchus. International Whaling Commission, Cambridge, UK.

Thomas, J.A., M. Stoermer, C. Bowers, L. Anderson and A. Garver. 1988. Detection abilities and signal characteristics of echolocating false killer whales (Pseudorcacrassidens). Pages 323-328 in P.E. Nachtigall and P.W.B. Moore (eds),Animal Sonar. Plenum Publishing Corporation, New York.

Awbrey, F.T., J.A. Thomas and R.A. Kastelein. 1988. Low-frequency underwater hearing sensitivity in belugas, Delphinapterusleucas. Journal of the Acoustical Society of America 84:2273-2275.