Anthropogenic Noise Sources and Sound Production of Beluga Whales in Cook Inlet, Alaska
Marine Mammal Symposium poster
Beluga whales (Delphinapterus leucas) in Cook Inlet, Alaska are geographically and genetically isolated from other Alaska beluga populations, and were listed as endangered in 2008. One potential threat to the recovery of the population is anthropogenic noise, which may disrupt communication and normal behaviors throughout the population's limited range. In order to evaluate this potential problem, knowledge of anthropogenic noise sources and levels, and in-depth understanding of the animals' acoustic behavior is necessary. This project used a single boat-based hydrophone system to evaluate noise levels at several locations in Cook Inlet on 6 days from August 2-14, 2007. Belugas were encountered on two days during this period, at the Port of Anchorage and near the mouth of the Little Susitna River, and recorded vocalizations were analyzed to develop a preliminary catalog of the whales' vocal repertoire. Beluga vocalizations were measured and categorized into whistles, high-frequency whistles, and pulsed/noisy sounds. Most recorded vocalizations were similar to call types found in other beluga populations. Vocalization frequencies ranged from 0.381 kHz to 24 kHz, with most energy at frequencies above 2 kHz. Recorded noise sources included ships at and around the Port of Anchorage, commercial and military airplane over-flights, and tidal flow. Broadband and 1/3-octave band levels were evaluated for all anthropogenic and natural noise sources. Vessel noise levels were highest below 0.5 kHz, but frequencies ranged to greater than 8 kHz at the Port of Anchorage. Based on the overlap in frequency between beluga vocalizations and noise, anthropogenic sound can potentially interfere with beluga communication close to transiting and docked vessels in Cook Inlet.