What kills killer whales? Pathology reports of more than 50 killer whales in the northeast Pacific and Hawaii

Pathology reports of more than 50 killer whales stranded for nearly a decade in the northeast Pacific and Hawaii show orcas face a variety of deadly threats – many of which stem from human interactions.

A study analyzing the reports was published today (December 2) in the journal PLOS ONE. The results of the study indicate that understanding and being aware of each threat is critical to managing and conserving killer whale populations. It also presents a basic understanding of the health of orcas.

The study was conducted by a team of marine mammal specialists led by a veterinary pathologist from the British Columbia Department of Agriculture and coordinated by SeaDoc Society, a Washington-based program at the University of California, Davis’ School of Veterinary Medicine. The study received advice and support from the Department of Fisheries and Oceans Canada and NOAA Fisheries in the United States, the two federal agencies that manage this species.

Whales include those from healthy populations as well as endangered species, such as the southern resident whales regularly seen off the coasts of British Columbia, Washington state and Oregon.

Of 52 whales stranded between 2004 and 2013, the causes of death were determined for 42%. For example, a calf died of sepsis following an injury to a halibut hook. Another is starving for a congenital facial deformity. Two whales died from blunt trauma from collisions with ships. Other causes of death include infectious diseases and nutritional deficiencies.

“We can do better”

While there is no single common cause of death, the study found a common theme: Human-caused deaths have occurred in all age groups – from minors to subadults and adults.

“No one likes to think that we are directly harming animals,” said Joe Gaydos, director of the SeaDoc Society, wildlife veterinarian at the Karen C. Drayer Wildlife Health Center at UC Davis School of Veterinary Medicine. “But it’s important to realize that we’re not hurting them indirectly because of things like lack of salmon, vessel disruption, or toxins from the past. It is also collisions with ships and hooks. The fact that humans directly kill killer whales in all age groups is significant; that says we can do a better job.

Gaydos and senior author Stephen Raverty, a veterinary pathologist with the BC Ministry of Agriculture, jointly developed a standard killer whale autopsy protocol in 2004. Revised 2014 with assistance from Judy St. Leger , a pathologist working for SeaWorld, this guide has helped improve examinations of deceased whales.

“The results of systematic autopsies of dead killer whales in this review are unique and will establish critical baseline information to assess future mitigation efforts,” Raverty said. “This work contributes to a better understanding of the impacts of human activities and ongoing environmental events on killer whales.”

The authors acknowledge that the report is an incomplete picture of killer whale health and mortality. Necropsies can only be performed on whales found in an adequate condition to receive them, and even then the cause of death cannot always be determined. But the report offers one of the most comprehensive looks to date on the myriad of human and environmental threats affecting Killer Whales and can help inform strategies to better protect them.

Reference: “Pathological findings and correlation with body condition index in stranded killer whales (Orcinus orca) in the Northeast Pacific and Hawaii from 2004 to 2013 ″ by Stephen Raverty, Judy St. Leger, Dawn P. Noren, Kathy Burek Huntington, David S. Rotstein, Frances MD Gulland, John KB Ford, M. Bradley Hanson, Dyanna M. Lambourn, Jessie Huggins, Martha A. Delaney, Lisa Spaven, Teri Rowles, Lynne Barre, Paul Cottrell, Graeme Ellis, Tracey Goldstein, Karen Terio, Debbie Duffield, Jim Rice and Joseph K. Gaydos, December 2, 2020, PLOS ONE.
DOI: 10.1371 / journal.pone.0242505

Other co-authors include scientists from a wide range of institutions including Cornell University, NOAA Fisheries, Alaska Veterinary Pathology Service, Maryland Marine Mammal Pathology Service, UC Davis One Health Institute, Fisheries and Oceans Canada, Washington Department of Fisheries and Wildlife, Cascadia Research Collective. , University of Illinois-Brookfield, Portland State University, and Oregon State University.

Funding was provided by NOAA Fisheries and multiple grants from the John H. Prescott Marine Mammal Rescue Assistance Grant program. Additional support came from Fisheries and Oceans, Canada; Vancouver Aquarium Research Program; SeaDoc Society; Sea world; British Columbia Ministry of Agriculture Animal Health Center; Washington Department of Fish and Wildlife; and many First Nations, Alaskan Native and Inuit communities.