Phocoenacide: the killing of porpoise (Phocoenidae) by fish eating Southern Resident killer whales (Orcinus orca)

• Main Authors: Giles, Deborah, Smith, Courtney, Ellis, Samuel, Croft, Darren, Olson, Jennifer, Weiss, Michael
• Format: Text
• Language: English
• Published: Western CEDAR 2018
• Subjects: Fresh Water Studies; Life Sciences; Marine Biology; Natural Resources and Conservation; Terrestrial and Aquatic Ecology; Killer Whale; Orca; Orcinus orca; Killer whale
• Online Access: https://cedar.wwu.edu/ssec/2018ssec/allsessions/51

Southern Resident fish-eating killer whales have been observed "mugging" and killing harbor and Dall’s porpoise without subsequent predation on the animal carcass. While occasional porpoise killings by L-pod and K-pod members were documented by staff of the Center for Whale Research since regular monitoring started in 1976, prior to 2005, J-pod was rarely seen engaging in this behavior. However, in 2005, multiple different members of J-pod were documented killing harbor porpoises on five separate occasions during the month of July alone. Since 2005, more than 25 additional mugging episodes by members of all three Southern Resident killer whale pods have been documented with members of J pod participating in more than half. We investigate the cultural transmission of this unusual behavior through the southern resident killer whale community. Pooling long-term datasets from myriad research groups and whale watching vessel naturalists allows for robust analysis of this novel behavior with the aim of understanding why this behavior is occurring as well as possible implications for the local harbor porpoise population, a population already targeted as prey by mammal eating killer whales (Bigg’s killer whales) in the area.