Hearing Sensitivity of the Polar Bear with Implications for Environmental Disturbance in the Wild

Polar bears have recently been classified by the IUCN as "vulnerable." This dubious upgrade from "conservation dependent" marks a critical point in polar bear conservation efforts.

For millennia, the Arctic habitat of the polar bear has provided them with a protection that other temperate and tropical species of bear have not enjoyed. Limited human settlement guaranteed that the polar bear’s habitat was relatively pristine. Unfortunately, worldwide industrial practices now threaten the polar bear in a variety of ways. From a scientific standpoint, the best-documented impacts have been with bioaccumulation of various toxins in the fat and milk of female polar bears. Now, the general public has also become aware of the imminent threats of both global warming and the increased pressure to exploit the vast petroleum reserves of the Arctic region. Unfortunately for the polar bear, some of the highest concentrations of documented polar bear maternity dens are found in the same continental shelf regions that hold some of the most promising petroleum reserves.

Petroleum extraction involves a great deal of heavy industrial machinery and activity, and that means noise. But how disturbing is this noise to polar bears? When it comes to noise, one of the best tools to enable managers to assess the potential disturbance of a particular combination of loudness and pitch (a.k.a amplitude and frequency) is an understanding of the hearing sensitivity of the subject animal. These guidelines are used when protecting humans from industrial noise (We don’t figure out what bothers humans by blasting their ears with very loud noise!). In a nutshell, an understanding of how sensitive an animal’s hearing is allows us to estimate what types of loud noises would be either disturbing or damaging to either their social communication or ability to hear.

The polar bears, research team, and training staff at the San Diego Zoo and CRES, in collaboration with Polar Bears International and Hubbs-SeaWorld Research Institute, offer a fantastic opportunity to gather this information. In order to determine hearing non-invasively, the bear must be trained to respond when it hears a noise, whatever the frequency or amplitude. This psycho-acoustic method is the best way to assess hearing sensitivity, and this type of data simply cannot be collected from wild bears. It is expected that the data we compile will be incorporated into management guidelines used on the North Slope of Alaska and hopefully around the Arctic as a whole.

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News archives: San Diego Zoo Holds Press Conference Addressing Polar Bear Population Crisis; Polar Bears at San Diego Zoo Undergo Hearing Study
Mother-infant Relationships in Bear Species
Watch the San Diego Zoo's polar bears on Polar Cam.