Movement and dive behavior of beluga whales in Cook Inlet, Alaska

Limited information exists on the foraging behavior of the endangered population of beluga whales (Delphinapterus leucas) in Cook Inlet, Alaska, especially during the winter months with heavy ice-cover. We used satellite telemetry to record the movement and diving behavior of whales across 3 years (1999-2003), including the winter months. Whales remained in Cook Inlet the entire time they were tracked. Mean dive depths across the entire tracking period ranged from 1.6 to 6.7 meters and mean dive duration ranged from 1.1 to 6.9 minutes. Overall, dives were significantly shorter in the near-shore areas of Chickaloon Bay, Susitna Delta, Knik Arm, Turnagain Arm, and Trading Bay. This type of dive behavior, in combination with significantly slower transit rates, suggests that whales are likely foraging in these areas. While belugas tended to prefer shallow inshore waters throughout the year, the presence of sea ice between December and May may prevent access to coastal areas. Preference for pack ice, despite the large proportions of Cook Inlet remaining ice-free, may be an indication of belugas attempting to access coastal areas despite increased ice concentration. With the declining abundance of Cook Inlet belugas, identifying potential foraging areas during ice-covered and ice-free periods is critical to the recovery of this endangered population.