Look at these sleepy seals. Maybe they ate too much, or maybe they're just exhausted from being around their family members. Regardless, these zonked-out pinnipeds are you, and me, and probably everyone else this holiday season.
What's cool about this footage, though, is that it's the first time Mediterranean monk seals, or Monachus monachus, have ever been recorded sleeping underwater. Scientists know the seal can hold its breath for up to 10 minutes at a time, but so little is known about the endangered species—a mere 600 individuals are believed to exist—that speculating about their snoozing habits has been prohibitively difficult.
Their closest relative, the Hawaiian monk seal (Neomonachus schauinslandi), has occasionally been known to doze off in small caves beneath the waves, but as marine biologist Alexandros Karamanlidis told New Scientist, this behavior was previously unheard of in the Mediterranean species.
"We had never seen Mediterranean monk seals sleeping in the water before. Until now, we thought that they slept only on land, in remote, inaccessible marine caves," said Karamanlidis, who currently works at MOm/Hellenic Society for the Study and Protection of the Monk Seal, an environmental NGO and member of the International Union for Conservation of Nature.
Mediterranean monk seals, like their Hawaiian and Caribbean counterparts, are teetering on the edge of extinction. These large, doe-eyed mammals are adept swimmers and skilled hunters, but fatal run-ins with fishermen, ocean debris, industrial pollution, and viral outbreaks caused their numbers to plummet during the 20th century. Today, the species is considered one of the most endangered EDGE—which stands for "evolutionarily distinct and globally endangered"—mammals on Earth.
Despite the Mediterranean monk seal's tragic legacy, the species has been fascinating humans for at least 2000 years. Homer, Plutarch, and Aristotle each described the animal in their works, and a coin minted circa 500 BCE even features the head of a monk seal. If we're to believe the ancient writings of the Greeks, the species was also considered to be culturally sacred, thus warranting the "protection" of deities Poseidon and Apollo.
Today, biologists are especially intrigued by the seal's penchant for marine caves. Mediterranean monk seals once birthed their pups on the vast sandy shores of Atlantic and west Mediterranean coastlines, but now almost exclusively retreat to isolated cave systems to rest and care for their young. The caverns selected by seals generally possess entrances above and below the water, and must contain dry beaches for mothers and their babies. More than 500 caves have been utilized by a subpopulation in Greece.
Around 1997, a mass die-off of 100 individuals is believed to have occurred near the Cap Blanc Peninsula of Western Sahara, after dinoflagellate plankton caused a toxic red-tide (or algal bloom) to flood the area.
On a happier note, Karamanlidis hopes the footage of sleepy monk seals will actually strengthen conservation efforts around the species. Now that scientists know the seals sometimes nap underwater, he told New Scientist, protected areas should be widened to include the coastlines where they might happen to be catching some shuteye.