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Research by Jennifer Tennessen shows that decline in southern resident orcas may be explained by hunting behavior

Friday, March 10, 2023 - 13:45

In partnership with NOAA Fisheries, UW News has posted a press release about new research -- led by UW and NOAA scientists -- on the hunting behaviors of northern and southern resident orcas in the Pacific Northwest and British Columbia.

Southern resident orcas have experienced no net population growth since the 1970s, with just 73 left at the most recent count. But northern resident orcas, which have a similar diet, territory and social structure, have grown steadily, now numbering more than 300. This new study, which was published recently in Behavioral Ecology, may help explain why: The two populations differ significantly in how they hunt for salmon, their primary and preferred food source. Conservationists will have to take these key differences into account when designing interventions to help southern residents.

Lead author on the paper is Dr. Jennifer Tennessen, who conducted this study as a research scientist with NOAA’s Northwest Fisheries Science Center. Dr. Tennessen is now a senior research scientist at the UW’s Center for Ecosystem Sentinels in the Department of Biology.

“For northern resident orcas, females were hunting and capturing more prey than males. For southern resident orcas, we found the opposite: The males were doing more hunting and capturing than females,” said lead author Jennifer Tennessen, a senior research scientist at the University of Washington’s Center for Ecosystem Sentinels. “We also found that if their mother was alive, northern resident adult males hunted less, which is consistent with previous work, but we were surprised to see that southern resident adult males hunted more. Adult females in both populations hunted less if they had a calf, but the effect was strongest for southern residents.”

Read the full article in UW News.

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