Dive behavior, feeding ecology and site fidelity of resident gray whales, Eschrichtius robustus, in Queen Charlotte Strait, British Columbia, Canada
Michelle Kinzel
Moss Landing Marine Laboratories, PO BOX 450 Moss Landing, CA 95039-0430
On 16 June 1994, the gray whale was the first of the great whales to be removed from the U.S. List of Endangered and Threatened Wildlife. As the gray whale population has recovered from threats of extinction, political and economic decisions concerning its breeding and feeding grounds have shifted. With the increase in population numbers came a concurrent reduction in protective measures concerning the species' and its habitat. For example, the Makah Indians of Washington State have been granted permission to renew tribal whaling practices and the United States has once again become a whaling nation. A thorough understanding of gray whale migratory behavior and ecology is necessary to assess the dynamics of a once-endangered species after it has been removed from political protection. This study examines individual foraging and ventilatory patterns of feeding gray whales inhabiting a tertiary feeding ground located in Queen Charlotte Strait, British Columbia. Ventilation and diving patterns of individual gray whales were recorded during June, July and August of 1996, 1997 and 1998. Dive times, surface durations, number of blows and blow interval lengths were compared in the two behavioral categories of feeding and traveling. Statistical differences were detected among individual whales and between the two behavioral categories for dive time, surface duration, number of blows per surface duration and blow intervals. Diving patterns were examined for the number of dives per hour and are reported as 21.4-27.31 dives per hour for feeding whales and 15.67-26.05 dives per hour for traveling whales. The assessment of dive patterns determined that the majority of time was spend diving, ranging from 77.0 to 85.8% of total time. In addition, site fidelity and habitat utilization were assessed to determine whether gray whales are selecting the most favorable feeding sites in terms of prey availability. Prey densities and predatory behavior are crucial components of optimal foraging theory. This information may prove valuable for future management decisions concerning gray whale habitat.
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