When it comes to ocean diving, no seal can compete with the elephant seal. While on the hunt for their deep-dwelling squid and fish prey, these blubbery behemoths hold their breath for up to two hours and can plunge a mile beneath the surface; they skirt hungry orcas and withstand pressures that would flatten a junkyard car.
These epic dives help the seals survive long stints at sea, including the thousands-mile-long foraging trips they embark on each year, some of which take the animals from the west coast of North America to the middle of the Pacific and back. The animals swim and dive almost constantly for about seven months straight, never once going ashore to rest. And for decades, researchers such as Daniel Costa, a marine biologist at UC Santa Cruz, couldn’t help but marvel at the marine mammals’ stamina—and wonder how, and when, they possibly slept. There were only two possibilities, Costa told me: “They must sleep somewhere out there. Or maybe they don’t.”