Science & Nature

Greenland sharks: The longest-living vertebrates

A Greenland shark swimming in the St. Lawrence River estuary in Canada.



A Greenland shark swimming within the St. Lawrence River estuary in Canada.
(Image credit score: Doug Perrine/Alamy Stock Photo)

Greenland sharks (Somniosus microcephalus) belong to a household of sharks known as sleeper sharks, which transfer slowly and stealthily by the water. They are the longest-living vertebrates, or animals with backbones, surviving for as much as a whole bunch of years within the deep, chilly waters of the Arctic and North Atlantic oceans. 

These sharks sneak up on dwell prey and scavenge useless animals, together with different sharks, seals, drowned horses and polar bears. Scientists are studying an increasing number of about these mysterious sharks that not often encounter people, however there are nonetheless many unknowns surrounding their existence. 

How huge are Greenland sharks?

Greenland sharks are among the many largest sharks on this planet; they develop as much as 24 toes (7.3 meters) lengthy and weigh as much as 2,645 kilos (1,200 kilograms), based on the St. Lawrence Shark Observatory (ORS). That’s longer than nice white sharks (Carcharodon carcharias), that are estimated to develop as much as 20 toes (6 m) lengthy, with unconfirmed stories suggesting they’ll attain 23 toes (7 m) in size, based on the Florida Museum of Natural History. 

Key info

Size: Up to 24 toes (7.3 m)

Life span: 272 years (estimate)

Conservation standing: Vulnerable 

Greenland sharks have cylindrical our bodies that may be black, brown, grey or a mix of all three colours, they usually might have spots. These sharks even have teeth-like scales, known as dermal denticles, protecting the surfaces of their our bodies. The scales cut back drag and assist the sharks transfer extra silently by the water, based on the ORS. A Greenland shark’s mouth comprises 48 to 52 enamel in its higher jaw and 50 to 52 enamel in its decrease jaw. The higher enamel are pointed, to assist the sharks maintain on to bigger meals, whereas the decrease enamel are broad and curved sideways so the sharks can carve out spherical chunks of flesh from prey by shifting their head in a round movement, based on the ORS.

Ocean parasites known as Ommatokoita elongata are sometimes connected to the eyes of Greenland sharks. The parasite tends to dwell in simply one of many shark’s eyes, however this may nonetheless render the shark partially blind. Because the sharks rely extra on their different senses to catch prey at the hours of darkness ocean waters, the parasites do not appear to have an effect on the sharks a lot, based on the Florida Museum of Natural History. 

Related: Ancient Greenland shark reveals its age in eerie underwater video

How lengthy do Greenland sharks dwell?

Greenland sharks’ actual life span is unknown, however they’re thought of the longest-living sharks, and the longest-living vertebrates, on this planet. A 2016 examine of the sharks’ eye tissue printed within the journal Science estimated that Greenland sharks have a most life span of no less than 272 years. Researchers estimated that the oldest Greenland shark in that examine was about 392 years outdated, however the estimate had a big margin of error of 120 years, which led to hypothesis that Greenland sharks may dwell to 512 years outdated. The estimated vary hasn’t been verified.

“It’s vital to remember there’s some uncertainty with this estimate,” Julius Nielsen, co-author of the 2016 paper, beforehand informed Live Science. “But even the bottom a part of the age vary — no less than 272 years — nonetheless makes Greenland sharks the longest-living vertebrate identified to science.”

Greenland sharks dwell within the sluggish lane, with a high swimming pace of lower than 1.8 mph (2.9 km/h). They additionally develop slowly at lower than 0.4 inch (1 centimeter) per yr and have sluggish metabolisms, based on the National Oceanic and Atmospheric Administration (NOAA). Scientists do not but know the way Greenland sharks dwell so lengthy however it could be linked to their sluggish lifestyle.  

Related: No, scientists have not discovered a 512-year-old Greenland shark

Where do Greenland sharks dwell?

Greenland shark swimming, Somniosus microcephalus isolated on black background.

Greenland shark swimming remoted on black background. (Image credit score: dotted zebra / Alamy Stock Photo)

Greenland sharks dwell within the Arctic and North Atlantic oceans from North America to Greenland and from Portugal to the East Siberian Sea, based on the International Union for Conservation of Nature (IUCN). The sharks have a wide variety and might be discovered swimming from the floor right down to depths of 8,684 toes (2,647 m), the IUCN says. 

Scientists nonetheless have a lot to study how Greenland sharks dwell and reproduce. Female Greenland sharks give start to dwell younger, known as pups, that hatch from delicate eggs that the females carry inside their our bodies. In a 2020 examine printed within the journal PLOS One, researchers estimated that Greenland sharks give start to between 200 and 324 pups per being pregnant, relying on the dimensions of the shark. Greenland shark pups are simply 14 to 18 inches (35 to 45 centimeters) lengthy after they’re born. 

What do Greenland sharks eat?

Greenland sharks have a various weight-reduction plan that features fish, different sharks, eels and marine mammals, resembling seals. They have additionally been discovered with drowned land animals, together with horses and reindeer, of their stomachs, and have been seen in giant numbers on the sea floor, feeding collectively on the stays of whales and fish killed throughout business whaling and fishing, based on the University of Michigan’s Animal Diversity Web (ADW). 

Greenland shark taxonomy

Kingdom: Animalia

Phylum: Chordata 

Class: Chondrichthyes

Order: Squaliformes

Family: Somniosidae

Genus and species: Somniosus microcephalus

Source: ITIS 

Scientists discovered a Greenland shark with the jaw of a younger polar bear (Ursus maritimus) in its abdomen, Reuters reported in 2008. The researchers had been uncertain the way it received there; however most shark specialists believed that the polar bear was possible already useless when the shark ate it, as dwell polar bears are too harmful for the sharks to tackle. Researchers additionally discovered some polar bear muscle tissue and pores and skin within the abdomen of one other Greenland shark throughout a 2014 examine printed within the journal Polar Biology, they usually concluded that the bear was possible scavenged fairly than hunted.  

Greenland sharks are close to the highest of the meals chain, however sperm whales (Physeter macrocephalus) might hunt them. Chris Harvey-Clark, co-founder of the Greenland Shark and Elasmobranch Education and Research Group (GEERG, now the ORS), wrote in Capeia, a web-based science communication journal, about recording a Greenland shark seemingly fleeing from the echolocation clicks of a foraging sperm whale. Upon its dying, that sperm whale was discovered with its enamel worn right down to stumps, much like these of orcas (Orcinus orca) that feed on Pacific sleeper sharks (Somniosus pacificus), that are carefully associated to Greenland sharks and have equally robust pores and skin. As such, Harvey-Clark theorized that the sperm whale hunted Greenland sharks. Scientists are but to look at sperm whales looking these sharks elsewhere.

Related: Sperm whales outwitted Nineteenth-century whalers by sharing evasive ways

Are Greenland sharks harmful?

There are not any verified stories of a Greenland shark attacking a human. However, some anecdotal proof means that such assaults may happen. GEERG divers noticed a Greenland shark “stalk” a crew of divers. They have additionally seen Greenland sharks examine diver actions as in the event that they had been scouting seal prey, based on the ORS. A Greenland shark was reportedly discovered with a human leg in its abdomen off Canada’s Baffin Island round 1859, however this report was not verified.

Untreated Greenland shark meat is poisonous to people, because it comprises excessive ranges of trimethylamine oxide (TMAO), which breaks down into the toxic trimethylamine (TMA) compound throughout digestion, based on a 1991 examine printed within the journal Toxicon. TMA could cause extreme intestinal issues and produces comparable results to extreme alcohol consumption. Greenland shark meat is edible solely when dried. The dried meat is fed to sled canine in northern areas resembling Greenland, based on the Florida Museum of Natural History. The shark can also be fermented and consumed as a delicacy in Iceland.

A photo of Greenland shark meat hanging in an open warehouse in Iceland

Greenland shark meat hanging in an open warehouse in Iceland, the place it’s a delicacy known as Hákarl. (Image credit score: jedamus/Shutterstock.com)

Are Greenland sharks endangered?

The IUCN considers Greenland sharks to be weak to extinction. Humans killed Greenland sharks for his or her liver oil to make use of in lamps and different merchandise between the thirteenth and twentieth centuries. The business fishing of Greenland sharks for his or her oil ended by the Sixties, which helped their inhabitants. However, Greenland sharks proceed to be caught and killed as bycatch, or animals that get pulled up by fishers alongside their supposed catch, for instance, in giant nets dragged alongside the underside of the ocean supposed to catch numerous fish. Most of the Greenland sharks eaten by people and fed to canine come from bycatch, though some sharks are targetted on a small scale.  

The Northwest Atlantic Fisheries Organization (NAFO), an intergovernmental fishing science and administration physique, prohibits the direct fishing of Greenland sharks and seeks to cut back bycatch. The NAFO applies to most fisheries within the Northwest Atlantic ocean and consists of nations such because the U.S. and Canada. The IUCN recommends additional protections, resembling bycatch coverage, be developed for Greenland sharks and enforced. 

The IUCN estimates that the Greenland shark inhabitants has declined by 30% to 49% over the previous 450 years, or three shark generations. However, this decline was estimated primarily based on a conservative Greenland shark life span of 150 years; the decline might be a lot larger if the sharks have longer life spans, as it might take them longer to achieve reproductive age and produce extra sharks. The international Greenland shark inhabitants dimension is unknown. Climate change can also be hurting the species — for instance, by lowering Arctic sea ice, which provides fishing fleets simpler entry to Greenland shark habitat. 

Additional sources

  • See pictures and movies of a Greenland shark and different deep sea creatures encountered throughout the NOAA Northeast U.S. Canyons Expedition in 2013.  
  • Watch this brief video on YouTube about how Greenland shark meat is ready and consumed in Iceland, from Food Insider.
  • Learn extra about the place Greenland sharks dwell with an interactive map, from the Encyclopedia of Life. 
Patrick Pester

Patrick is a employees author for Live Science. His background is in wildlife conservation and he has labored with endangered species all over the world. Patrick holds a grasp’s diploma in worldwide journalism from Cardiff University within the U.Okay. and is presently ending a second grasp’s diploma in biodiversity, evolution and conservation in motion at Middlesex University London.

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