For deep-diving elephant seals, it takes lots of work to stay fat

May 13 – For elephant seals – one of probably the most distinctive of the 33 species that comprise the world’s seal household – it is tough work to stay fat.

Scientists have performed probably the most thorough research to date of the distinctive feeding habits of northern elephant seals, specializing in the females of the species throughout arduous two-month post-breeding migrations within the northeastern Pacific Ocean.

The seals have been discovered to spend upwards of 20 hours day by day – and generally a full 24 hours – in steady deep-diving to feed on multitudes of small fish, fairly than the bigger prey favored by different deep-diving marine mammals, to achieve the physique fat important for profitable replica and insulation within the frigid depths. They fed 1,000 to 2,000 occasions each day.

“It is not easy to get fat,” mentioned marine biologist Taiki Adachi of the University of St Andrews in Scotland, who led the research printed this week within the journal Science Advances.

The researchers tracked 48 feminine elephant seals from Año Nuevo State Park in California, website of an vital breeding colony, as they lined huge ocean distances. Their round-trip migration was up to round 3,700 miles.

They primarily based their findings on knowledge obtained from 2011 and 2018 utilizing three small detachable units: one connected below the jaw that counted the quantity of occasions they fed and measured their depth; a satellite tv for pc tracker connected atop the pinnacle that offered location data; and a “smart” video digital camera with an infra-red LED mild flash, movement tracker and one other depth sensor, additionally atop the pinnacle.

Elephant seals get their title from the distinguished noses of the males that resemble an elephant’s trunk. There are two species – the northern elephant seal and the marginally bigger southern elephant seal. The two are the world’s greatest seals and the biggest marine mammals aside from whales.

A female northern elephant seals equipped with bio-logging electronic tags to track its deep-ocean foraging behaviour is depicted in an undated illustration.
A feminine northern elephant seals outfitted with bio-logging digital tags to monitor its deep-ocean foraging behaviour is depicted in an undated illustration.

Male northern elephant seals might attain 13 ft lengthy and weigh up to 4,500 kilos (2,000 kg). Females are considerably smaller, getting up to about 10 ft in size and 1,300 kilos. The males feed solely in coastal waters.

Some massive marine mammals rely on deep dives to forage for meals, with extra meals wanted primarily based on the animal’s measurement. Sperm whales, maybe the heavyweight champions of the deep dive, hunt for big prey like big squid.

The feminine elephant seals, additionally massive however not on the dimensions of a sperm whale, have devised a unique answer – consuming big quantities of small fish. But it is laborious to catch sufficient small fish to meet the vitality wants of such a big animal.

“They continuously dive, for long periods of time – 20 minutes on average and about 100 minutes at maximum – and deep – 1,640 feet on average and about 4,920 feet at maximum – with only a few minutes breathing at the surface,” Adachi mentioned.

“During the two-month migration, they never come back to the land. The sleeping hours in at-sea animals is not fully understood. But, based on our record of extreme foraging, their available time for sleeping should be less than 20 percent of the day,” Adachi added.

The vary of the northern elephant seal spans the Pacific coast of the United States, Canada and Mexico. They usually breed and provides start in California and Baja California, often on offshore islands, from December to March and quick throughout mating season, shedding maybe a 3rd of their physique weight.

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