Nice guys might finish last, but it’s one mean shark that’s dying last. The Greenland shark has attained rank as the longest living vertebrate on the planet. It didn’t achieve this Guinness Book of World Records status by being nice though, far from it. Its long life includes many strange phenomenon and gruesome habits. Here’s why these sharks live so long.

Greenland sharks in slow motion

It’s probably no coincidence that the Greenland shark, Somniosus microcephalus, is part of the “sleeper shark” family. Not because it’s known for dozing, no, more because it lives life in super slow motion. They cruise the deep about 9,100 feet down at speeds of about 1 foot per second. And while they’re huge, up to 24 feet long and weighing as much as 2,645 pounds, they’re not threatening to humans, according to the Greenland Shark and Elasmobranch Education and Research Group (GEERG). While they’ve been known to toss Inuit kayaks around a bit, humans can avoid the threat posed by eating them. That’s right, the Greenland shark has toxic flesh. When another animal bites in, the trimethylamine oxide from the shark becomes trimethylamine proper, a substance that smells like a cat box combined with dead fish. This has a sort of alcohol-overdose neurological effect on the diners and can cause death or just extreme abdominal discomfort.

Another creepy–fascinating trait of the Greenland shark is the wormlike parasites that dangle from the corner of its eyes, blinding it a bit. And the shark’s skin is covered all over in these teeth constructed like fish scales, called dermal denticles. These help the Greenland shark swim stealthily, if slooooowly. They also deter diver interactions, since drysuits get punctured if they come in contact with dermal denticles.

This shark will eat anything

This is no gentle giant. The Greenland shark is a vicious hunter able to ramp up speed just long enough to kill seals and other larger mammals, like the beluga whale. And just like Wild West posters, “wanted dead or alive” is this opportunistic scavenger’s motto. Scientists have verified Greenland shark stomach contents including Atlantic salmon, jellyfish, skates, other sharks, porpoise, and seals. They have also found Greenland sharks who ate polar bear remains, though they probably didn’t kill it, a dog and a horse. One theory is that the sharks feed on caribou, reindeer, and moose who drown by falling through the ice during migration.

But don’t credit or blame Greenland for this shark. It’s not endemic to that country and can be found other places than the Arctic Ocean. One place the longest-living vertebrate frequents is the St. Lawrence Estuary and Gulf, for example.

Who knows how old?

For all scientists know, there are Greenland sharks who were alive with Leonardo Da Vinci, who died May 2, 1519. But the best guess comes from a 2016 study that analyzed 28 female Greenland shark using eye lens tissue and radiocarbon dating. It’s easier to establish shark ages by counting stripes in calcified vertebrae or spines from their fins, sort of like tallying a tree’s rings to establish their age. But the Greenland shark is too soft for this.

While the study didn’t pinpoint a specific Greenland shark that was 500 years old, the eye tissue analysis did conclude, with 95 percent accuracy, that the sharks were all at least (at least!) 272 years old. It further projected that 390 years was an average Greenland shark life span, with the total age range going up to 512. The reasons for this slow aging could come from its molasses-paced metabolism, slow growth rate–about a centimeter per year–or the frigid waters where it makes its home. But study co-author Julius Nielsen, a marine biologist and doctoral candidate at the University of Copenhagen, isn’t drawing any conclusions at the moment. “I’m just the messenger on this,” he told the New Yorker. “I have no idea.”