13: Baseline Hearing Measurements in Alaskan Belugas

While hearing is the primary sensory modality for odontocetes, there are few data addressing baseline hearing and subsequent variation within a natural population. To determine the effects of noise on marine mammals we need to understand what they hear. This is imperative in the Arctic where there is both an increase in human activity and a concurrent increase in human-produced noise. This work examines the hearing sensivitiy and variability of wild beluga whales in an effort to understand how belugas may be impacted by noise. A standard audiogram was determined from the wild animals, noting the variation between animals and the audiogram of maximal and minimal sensitivity. These novel data were compared to available hearing results from captive belugas, evaluating differences and variation within the two data sets. The hearing curves were appraised relative to basic demographic meta-data from the animals from which the measurements were made. Through these data analyses we sought to: 1) define the natural and baseline hearing abilities and variability in belugas, 2) place the results in the context of potential ecological influences and that of anthropogenic noise, and 3) evaluate the validity of captive-based hearing data in relation to wild animals. This is part of a larger effort to understand variation in the sensory biology and noise susceptibility of diverse odontocete species.