A new study of iconic but endangered killer whales living in southern British Columbia found that for years animals faced dietary deficiencies: getting 17% less food than they needed.
The ongoing malnutrition of killer whales could help illustrate why they have not been able to rebuild their population, according to the study’s lead author, Fanny Couture, of the UBC Institute for Oceans and Fisheries.
“There’s a big question of trying to understand why this population can’t thrive,” he said. “If you think about a human being, if you don’t eat enough, you’ll find yourself unable to do other things, like socialize, for example.”
Only about 75 southern residents remain, despite several promising pregnancies and births in recent years.
Couture and his team of scientists at the University of British Columbia published their findings in the journal Public Library of Science this week.
The new study is the latest to sound the alarm about the nutritional health of southern residents.
Ottawa considers them endangered and launched an “enhanced recovery plan” in 2019. And the U.S. government’s National Oceanic and Atmospheric Administration (NOAA) said in January that they “continue to face a high risk of extinction and should remain in danger of extinction “.
Killer whales are shown at Chatham Sound, near Prince Rupert, BC, on June 22, 2018. (Jonathan Hayward / The Canadian Press)
UBC researchers examined the abundance of its main food source, chinook salmon, chum salmon and coho, in the frequent areas of killer whales over a four-decade period.
Killer whales need to eat 170,000 calories every day, Couture said. This is approximately the amount of calories that 85 humans eat each day.
But for six of the last 40 years, southern residents have not had enough to eat, the study showed.
“The study highlights the urgency of doing something for killer whales,” Couture said. “And what can be done is to really look at the different factors that could affect these prey populations.”
The southern resident killer whale is one of three types of killer whale found in BC waters, the others are transient or Bigg’s killer whales and northern residents. Southern residents eat fish, mostly Chinook salmon, and its distribution extends from southeast Alaska to central California; while transient killer whales have a more varied and flexible diet.
Another study, published last August in the journal Ecosphere, found that between 2008 and 2019, southern resident killer whales with “depleted fat reserves” faced double or triple death rates. ‘those with healthy body conditions.
Experts say a decline in southern resident killer whale populations is likely due to a combination of factors, such as noise from shipping, pollution of their habitats, and declining numbers of Chinook salmon.
Couture said his team’s next step is to look at the same 40-year-old data for the northern resident population, which is much larger.
To learn more about threats to southern resident killer whales and efforts to save them, check out the original CBC British Columbia Killers: J pod on the brink podcast, presented by Gloria Macarenko.