Elephant seals redefine ‘deep sleep’

Northern elephant seals get just two hours of sleep at sea, taking deep dives below predators

When they’re on the land, northern elephant seals can look pretty lazy. But in the water, they live active lives. They have to swim, feed and avoid getting eaten. How do they find time to sleep? They don’t, researchers found. At least not much.

In a study published in Science, researchers found that northern elephant seals (Mirounga angustirostris) get by on about two hours sleep. That puts them on par with the land animal they share their name with—the African elephant (Loxodonta spp.). When they haul out on land, elephant seals log over 10 hours a day. But during the seven months they spend feeding at sea, they plunge hundreds of feet below the surface to get brief naps away from great white sharks (Carcharodon carcharias) and killer whales (Orcinus orca).

To learn about their sleeping patterns, researchers fitted elephant seals with a sort of night cap that measured their brain waves, heart rates and movement. Lead author Jessica Kendall-Bar, a researcher at the University of California, Santa Cruz, hopes the findings can aid conservation.

“Learning more about where, when and how marine mammals sleep at sea can help scientists improve the management of their critical resting habitats,” she told the New York Times.

Read more from the New York Times.


Header Image: Northern elephant seals spend long hours sleeping on land, but at sea, they get by on two-hour naps. Credit: Ashley Spratt/USFWS