In-Air Auditory Psychophysics and the Management of a Threatened Carnivore, the Polar Bear (Ursus maritimus)
Management criteria for preventing biologically-significant noise disturbance in large terrestrial mammals have not been developed based on a sound, empirical understanding of their sensory ecology. Polar bear (Ursus maritimus) maternal denning areas on the coastal plain of Alaska’s North Slope hold large petroleum reserves and will be subject to increased development in the future. Anthropogenic noise could adversely affect polar bears by disrupting intra-specific communication, altering habitat use, or causing behavioral and physiological stress. However, little is known about the hearing of any large, carnivorous mammal, including bears; so, management criteria currently in use to protect denning female polar bears may or may not be proportionate and effective. As part of a comprehensive effort to develop efficient, defensible criteria we used behavioral psycho acousticmethods to test in-air hearing sensitivity of five polar bears at frequencies between 125 Hz and 31.5kHz. Results showed best sensitivity between 8 and 14 kHz. Sensitivity declined sharply between 14and 25 kHz, suggesting an upper limit of hearing 10-20 kHz below that of small carnivores. Low frequency sensitivity was comparable to that of the domestic dog, and a decline in functional hearingwas observed at 125 Hz. Thresholds will be used to develop efficient exposure metrics, which will be needed increasingly as the Arctic is developed and effects of disturbance are intensified by anticipated declines in polar bear health and reproduction associated with climate change driven sea ice losses.