Asphyxiation of an endangered Cook Inlet beluga whale, Delphinapterus leucas

Abstract

The isolated population of Cook Inlet beluga whales, Delphinapterus leucas, is endangered under the U.S. Endangered Species Act (ESA). They reside year-round in the Cook Inlet tidal estuary in southcentral Alaska, near Anchorage. Due to their ESA status, information on causes of mortality are important. A dead beluga was reported in Turnagain Arm, Cook Inlet, on 7 Oct. 2013, and a necropsy was performed two days later. The beluga was a robust, apparently healthy adult male ∼40 years old. Cause of death was determined to be asphyxiation caused by a starry flounder, Platichthys stellatus, found lodged in the pharynx at the goose beak, dislocating the larynx. Prey anatomy such as spines, body shape, and backbone rigidity may increase the risk of choking in beluga whales and other cetaceans. This is the first known death by asphyxiation of the 49 Cook Inlet beluga deaths investigated in the last 18 years, indicating that it is rare and not likely to be a significant cause of mortality. It is important, however, to monitor and document all sources of mortality given the status of this endangered population.