The Endangered Beluga Whales of Cook Inlet, Alaska

Beluga whales and narwhals (Monodon monoceros) are the only living species in the family Monodontidae. The common name beluga is derived from the Russian word for white, belukha; the species name leucas also means white and refers to the skin color of adult whales. Beluga calves are dark brown or blue-gray. As they age, their skin turns progressively whiter, becoming pure white by about age 9, though some females may retain some gray coloration up to 21 years. The lifespan of these whales may exceed 60 years (based on counts of layers deposited in beluga teeth). The physical and behavioral characteristics described here vary among beluga populations but in general provide a good overall description of the species. Among whales, belugas are medium-sized (3.5-5.5 m in length) and weigh up to l,500 kg. Beluga whales are sexually dimorphic with males being significantly larger than females of the same age. Unlike most whales, belugas do not have fused cervical vertebrae, allowing neck flexibility. Adaptations to the cold environment include a thick insulating layer of blubber; a relatively small head, fluke, and flippers; a lack of a dorsal fin; and a tough dorsal ridge with little or no innervation—an advantage when breaking through sea ice.

Beluga whales (Delphinapterus leucas) reside year-round in the waters of Cook Inlet, Alaska, where they are accessible to residents and visitors of the state's largest city, Anchorage, home to 42 percent of the state's population. Concern about the high level of human-caused mortality on this small population of whales prompted the NOAA Fisheries to designate Cook Inlet beluga whales as depleted under the U.S. Marine Mammal Protection Act in 1999. With an estimated decline of nearly 50 percent between 1994 and 1998, the Cook Inlet population has remained between 300 and 400 animals since 1999. The failure of the population to recover led to an endangered listing under the U.S. Endangered Species Act in October 2008. As of June 2010, the population still only numbered about 340 beluga whales.