Endangered predators and endangered prey: seasonal diet of Southern Resident killer whales

Understanding diet is critical for conservation of endangered predators. The Southern Resident killer whales (SRKW) (Orcinus orca) are an endangered population occurring primarily in the west coast and inland waters of Washington and British Columbia. Insufficient prey has been identified as a factor limiting their recovery, so a clear understanding of the whales’ seasonal diet is a high conservation priority. Previous studies have shown that their summer diet in inland waters consists primarily of Chinook salmon (Oncorhynchus tshawytscha), despite this species’ rarity compared to some other salmonids. During other times of year, when ranging patterns include the U.S. and Canadian west coast and the northern and southern portions of the Salish Sea, their diet is largely unknown. To address this data gap, we collected feces and prey remains from October to May 2004-2017 in both the Salish Sea and U.S. west coast waters. Using visual and genetic species identification for prey remains and...