Leatherback sea turtle

Leatherbacks love to eat jellyfish.

Jellyfish are soft and squishy. The turtle has a pointy, sharp-edged mouth that helps it grab them and hold on.

Leatherbacks eat mostly soft, see-through ocean animals such as jellyfish and salps, which drift in the open sea. Now and then they also eat squid, crustaceans (the animal group crabs belong to), fish or seaweed.

Jellyfish are slippery, so the leatherback's body is built to hold them. Instead of the crushing beak other sea turtles have, it has sharp-edged jaws with a pointed tip on each side, and its throat is lined with spines that point backward so food cannot slide out.

The leatherback is a specialist predator of gelatinous zooplankton, mainly jellyfish and salps; Britannica adds squid, crustaceans, fish and seaweed as occasional foods. Heaslip and colleagues call this a low-energy food, so a leatherback must eat a great deal of it. Turtles filmed with animal-borne cameras off Cape Breton Island, Nova Scotia, ate an estimated average of 330 kilograms of jellyfish a day, about 261 lion's mane jellyfish; if the turtles weighed about 455 kilograms, as the researchers assumed, that is roughly 73 percent of their body mass (Heaslip and colleagues, 2012).

Its feeding anatomy reflects this diet. NOAA describes pointed, tooth-like cusps and sharp-edged jaws in place of the crushing beak of hard-shelled sea turtles, and backward-pointing spines in the mouth and throat that keep soft prey from escaping. The same preference has a cost: floating plastic bags can look like jellyfish, and swallowing them harms the turtle.

Leatherbacks are super travelers.

They swim across whole oceans to find jellyfish. Then they swim all the way back to warm beaches to lay eggs.

Leatherbacks make the longest journeys of any sea turtle. Some swim more than 16,000 kilometers in a year, traveling between feeding waters and nesting beaches. Scientists follow them with small satellite tags.

They are amazing divers too. A leatherback can dive about 1,200 meters down, deeper than any other turtle, and stay under for more than an hour before it comes up to breathe.

Leatherbacks undertake the longest migrations between breeding and feeding areas of any sea turtle. NOAA reports some averaging about 6,000 kilometers (3,700 miles) each way and some covering more than 16,000 kilometers (10,000 miles) in a year.

Satellite tagging has revealed how complex these routes are. Western Pacific turtles nest in Indonesia, Papua New Guinea and the Solomon Islands and cross the ocean to feed off the Pacific coast of North America. NOAA notes that summer and winter nesters from the same region follow different routes, toward northern or southern foraging grounds. Why they dive to about 1,200 meters is not fully known. Smithsonian Ocean reports a 2008 study suggesting the dives work as scouting trips: their jellyfish prey moves deep during the day and rises at night.

There are fewer leatherbacks than there used to be.

People help by keeping beaches dark at night and picking up plastic. Rangers and volunteers watch over nests so the babies can reach the sea.

Leatherbacks are listed as vulnerable worldwide, and some groups in the Pacific Ocean are in serious trouble. The biggest danger is getting caught by accident in fishing nets and lines. Taking eggs, losing nesting beaches and eating plastic by mistake also harm them.

You can help: use less plastic, and when you visit a nesting beach, keep lights off, fill in holes and stay well back from turtles and nests. Some of the most important beaches are protected by rangers and local people.

The IUCN Red List assessed the leatherback globally as Vulnerable in 2013. NOAA estimates the global population has declined about 40 percent over three generations, and the species is listed as endangered under the U.S. Endangered Species Act. Pacific populations are most at risk: nesting in the Eastern Pacific has fallen by more than 90 percent over three generations, and in Malaysia it went from about 10,000 nests in 1953 to fewer than one or two a year since 2003.

NOAA identifies bycatch in gillnets, trawls, longlines and buoy lines as the main global threat, followed by hunting and egg collection, loss of nesting beaches, artificial lighting, marine debris and changing ocean conditions. Responses include safer fishing gear, ranger patrols and community programs that protect nesting beaches (NOAA highlights partners in Indonesia and the Solomon Islands), and keeping beaches dark at night.