This study presents empirical data on predator numbers, movements and area usage, and predation obtained from tracking transient killer whales (Orcinus orca) throughout the inland waters of Southeast Alaska. From 1991-2007, 155 transient killer whales were documented via photo-identification methodology within this large study area (27,808 km2). Transient killer whales were distributed throughout Southeast Alaska and present during all seasons, although not all individuals were seen each year. Resighting data suggested that within Southeast Alaska maternal groups may partition area usage of their environment. By following whales for 1,467 km, we calculated a mean travel speed of 7.2 km/h with mean daily movements of 134 km ± 88 km/24 h, range 59-240 km/24 h. Photographic matches demonstrated that most (86%) of the transient killer whales identified in Southeast Alaska also utilized British Columbia and Washington State waters. In contrast, photographic matches between whales in Southeast Alaska and whales seen off of California were rare, suggesting that different transient killer whale stocks occupy these two regions. Transient killer whales preyed upon Dall’s porpoise (Phocoenoides dalli), Pacific white-sided dolphins (Lagenoryhncus obliquidens), harbor porpoise (Phocoena phocoena), minke whales (Balaenoptera acutorostrata), Steller sea lions (Eumetopias jubatus), harbor seals (Phoca vitulina), and seabirds. Potential prey species available but not targeted included humpback whales (Megaptera novaeangliae), elephant seals (Mirounga angustirostris), and sea otters (Enhydra lutris). Prey-handling techniques varied depending upon the prey being targeted with no evidence of prey specialization. During 114 encounters totaling 332.5 h of direct observations of transient killer whales, we documented 36 predation events for a calculated kill rate of 0.62 prey items/24-h period/whale. Data presented here provide a foundation of transient killer whale ecology aimed at improving our ability to understand the impact of transient killer whale predation on Southeast Alaska prey populations.
Key words: Kill rates, marine predator, area usage, prey handling, prey selection, Southeast Alaska, transient killer whales