Male killer whales hunt more than females

February 5, 2019, The Company of Biologists

 It's hard to tell just how imperilled killer whales are. With several different forms—some of which may even be different species—it's unclear which are at serious risk and which are less vulnerable. But one group is definitely in jeopardy. 'The southern resident killer whale population was listed as endangered in the United States in 2005', says Jennifer Tennessen from the National Oceanic and Atmospheric Administration (NOAA), USA and the decline of Chinook salmon in the Pacific Northwest—which are consumed by the population of ~75 whales—is believed to be one of the causes. While shipping also poses a risk to the animals, NOAA has been monitoring them for a decade and one of the scientists' main goals was to estimate how much fish the charismatic whales capture. But, with the majority of pursuits occurring beneath the waves, Tennessen and her colleagues needed to develop a technique based on the animals' manoeuvres that would allow them to identify when the mammals were successful. They publish their discovery that killer whale hunts are not always successful and that male killer whales hunt more than females in Journal of Experimental Biology.

Heading into the Salish Sea, between Vancouver Island, British Columbia and Washington State, Tennessen and her colleagues—Marla Holt, Candice Emmons, Brad Hanson, Jeff Hogan and Deborah Giles—attached tags to 21 whales to record their sounds and underwater movements. Then the team followed the animals, noting where they surfaced and what they were up to, in addition to retrieving the remains of any meals. 'Fieldwork is one of the most exciting yet simultaneously challenging aspects of the research', says Tennessen, describing how she and her colleagues tracked the animals from small inflatable boats in all conditions.

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