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Pathology reports of more than 50 killer whales stranded over nearly a decade in the Pacific Northeast and Hawaii show that orcas face a range of deadly threats, many of which stem from human interactions.
A study analyzing the reports was published in the journal today PLOS ONE. The study results indicate that understanding and awareness of each threat is critical to the management and conservation of killer whales. It also features basic knowledge of killer whale health.
The study was led by a team of marine mammal and killer whale specialists led by the British Columbia Department of Agriculture and coordinated by the SeaDoc Society, a Washington-based program of the University of California, Davis’ School of Veterinary Medicine. Lead author, Dr Stephen Raverty, and co-author, Dr John Ford, are contract professions at the University of British Columbia Institute of Oceans and Fisheries and the Department of Zoology, respectively.
Whales include both those from healthy populations and endangered species, such as southern resident whales regularly spotted off the coasts of British Columbia, Washington and Oregon.
Of the 52 whales trapped between 2004 and 2013, 42% of the causes of death were determined. For example, a calf died of sepsis as a result of a wound to the halibut hook. Another starved to death from a congenital facial deformity. Two whales died from violent trauma from ship impacts. 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: man-made deaths occurred in every age group, from young people to sub-adults and adults.
“In British Columbia, we lost nine southern resident killer whales: 2 adults, 2 sub-adults and 1 calf died from trauma; one was a confirmed propeller attack, with one adult and two sub-adults due to suspected ship strikes. “said lead author Stephen Raverty, a veterinary pathologist at the BC Department of Agriculture and an adjunct professor at the UBC’s Institute for Oceans and Fisheries. “One of these iconic species died from an infection secondary to satellite tagging. Another death was due to natural causes and the other two undetermined. Half of the southern killer whales identified in this study were caused by human interactions “.
“Nobody likes to think that we are directly harming animals,” said SeaDoc Society co-author and director Joe Gaydos, a 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 only harming them indirectly from things like salmon shortages, vessel disturbances, or inherited toxins. It’s also ship strikes and hooks. That humans directly kill killer whales of all age classes is. meaningful; he says we can do a better job. “
In 2004, Raverty and Graydos jointly developed a standardized killer whale necropsy protocol. Revised in 2014 with the help of Judy St. Leger, a pathologist working for SeaWorld, this guide has helped improve deceased whale examinations.
“The results of the systematic necropsies of dead killer whales in this review are unique and will establish critical background information for evaluating future mitigation efforts,” Raverty said. “This work contributes to a better understanding of the impacts that ongoing human activities and environmental events have on orcas.”
The authors acknowledge that the report is an incomplete picture of the health and mortality of the killer whales. Necropsies can only be performed on whales that are in an adequate state to receive them and, even then, the cause of death cannot always be determined. But the report offers one of the most comprehensive insights to date on the multitude of human and environmental threats affecting killer whales and can help define strategies to better protect them.
Source of the story:
Materials provided by University of British Columbia. Note: The content can be changed by style and length.
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