1/8/2023 0 Comments Orca predatorsBut the study does "provide some important baseline information of the health of the individual, and potentially, the overall population," he says.Įmaciated female killer whale (ID# 20081021) from Hawaii. "As only a small proportion of those killers that die in the wild are identified floating or are beach cast and available for necropsy, the samples we examined are biased," Raverty admits. Raverty notes 53 whales is a limited sample, so the researchers can't quantify how great a threat ship strikes pose to orcas. "With regards to ship strike, there have been anecdotal reports and published accounts of vessel and propeller strikes in killer whales, and results from the case series provide a forensic account or documentation to describe the effects of lethal impact with animals," Raverty says. The study reconfirms these vessel strikes not only happen but can prove fatal, underscoring humans' deadly impact on the marine world. Or they might die of blunt trauma after being hit by a fishing vessel, known as a vessel strike. They might suffer parasitic infections (toxoplasmosis) from polluted water. But the greatest common denominator, regardless of age, was death by humans.Ī whale might ingest a fishing hook or get tangled in a fishing net, for example. Younger and adult whales however suffered from toxic bacterial infections, disease, and blunt trauma. Together with photographs from each scene, the researchers were able to suss out the cause of death for 22 of the 53 whales.īaby whales most often died of infectious diseases and lack of nutrition. "With catastrophic traumatic injuries, we would anticipate an acute death of an animal whereas, with infections, tumors or extralimital events, loss of body condition related to insufficient caloric consumption may result in decline of the nutritional condition of animals," Raverty explains. Who's the real Killer? - Killer whales which died of blunt trauma - as opposed to an infection - had a higher score on the body condition index. Credit: Paul Cottrell / Fisheries and Oceans Canada Postmortem examination suggested he died from trauma consistent with vessel strike. The 18-year-old male southern resident killer whale, J034, stranded near Sechelt, British Columbia on December 21, 2016. Researchers measured the whales' blubber thickness to assess the length, health, age, and manner of death of the killer whales. "BCI is similar to the body mass index in people and has been developed to provide a quantitative assessment of the nutritional status of killer whales," Raverty says. Each whale's blubber's thickness ties back to a metric known as the body condition index, which measures the whale's health. And much like a toxicology report or an autopsy might reveal the killer in a human murder, the whales' blubber holds secrets to their tragic demise. To do this, they turned to what evidence they could gather from the dead whales themselves. So Raverty and his colleagues had to find ways to work around the lack of information. "For wild animals, aside from opportunistic or targeted field observations and use of drones to study body condition, oftentimes, there is little information available regarding the clinical history of wild stranded animals," Steve Raverty, lead author on the study and veterinary pathologist for the Canadian Ministry of Agriculture, tells Inverse. When you're looking at dead whales out in the wild, it's hard to get such a full picture of what went down. Most of the studies on the causes of killer whale deaths have involved orcas in captivity, which have ample medical records for scientists to draw upon. The researchers reviewed each wild whales' condition at the time of the death - something older research has just not done. They analyzed reports on the deaths of 53 stranded killer whales between the Eastern Pacific Ocean and Hawaii. A group of healthy killer whales swims in the Salish Sea with a Washington State Ferry in the background Photo Credit: Joe Gaydos, SeaDoc Society, UC DavisĪ Deadly Impact - In a first of its kind study, researchers sought to solve the mystery of what is killing the killer whales.
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