Predation by Killer Whales in Cook Inlet and Western Alaska: An Integrated Approach 2008-2009 Project R0303-01 Final Report

Killer whales are listed as a possible factor in the lack of recovery of the endangered Cook Inlet beluga whales. They have been suggested as agents in the decline of other marine mammal species as well. In this study, we develop research methodologies in False Pass/Unimak Island, Alaska and initiate pilot work photo documenting individuals and observing feeding ecology of killer whales entering Cook Inlet, Alaska. In False Pass/Unimak Island photo-identification coupled with satellite tracking indicated that over 100 killer whales feed on migrating gray whales during May and June. Using ARGOS telemetry we have determined that some killer whales remain in the area, but many move north into the Bering Sea, possibly following the gray whales. From 6 to 50 percent of the gray whale calf production may be taken in a given year, depending on the number of calves recruited. In fifteen encounters with killer whales in lower Cook Inlet, five were with mammal-eating transients. Sightings/photographs were also contributed by charter boats. Observed prey included non-calf humpback whales, minke whale, and sea otter. Weather, tidal conditions, and the infrequent encounter rates make work on killer whales entering lower Cook Inlet problematic. A sighting network, rapid response capabilities, and a systematic observer network in upper Cook Inlet are suggested in future examination of killer whale predation on beluga.