Greenland Sharks Can Live Hundreds of Years on Barely Any Food

Greenland sharks only need about 200g of fish per day to survive, scientists have discovered, potentially providing an insight into how they manage to live for hundreds of years.

By studying the metabolic rates of this vulnerable species, researchers led by Eric Ste-Marie, from the University of Windsor in Canada, have gained valuable information on this remarkable and understudied species in the face of anthropogenic pressures.

Greenland sharks are generally found in the colder waters of the North Atlantic and Arctic Oceans, as well as the seas surrounding Greenland. They are a large species and can grow up to around 20 feet in length, although most reach between eight and 15 feet.

It is one of the longest-lived animals on Earth, and the world's longest living vertebrate. Scientists believe they could live for 500 years.

Research published in Science in 2016 used atmospheric changes caused by nuclear bomb tests over several decades to estimate the ages of 28 Greenland sharks, the oldest of which was between 335 and 392 years old.

In a study published in the Journal of Experimental Biology, Eric Ste-Marie and colleagues examined the field metabolic rate of Greenland sharks. This is an indicator of how much food an animal needs to survive day to day.

They caught 30 Greenland sharks over the course of five years, which were tagged, sampled and fitted with biologger packages, the latter of which collected information on their movements, body temperature and water temperature.

Results showed the species was very lethargic, moving around at a very slow rate.

Using this information, the team was able to determine the daily calorie requirements of Greenland sharks, finding that an individual weighing around 500lbs needed to eat between two and 6.5 ounces of fish or marine mammal prey to survive.

This is far lower than other large shark species that live in warmer waters and swim fast. Research published in 2013 estimated that a great white shark weighing 2,000lbs would need to eat 66lbs of blubber every 11 days to survive.

Vincent Raoult, Postdoctoral Researcher at the School of Environmental and Life Sciences at the University of Newcastle, Australia, who was not involved in the research, told Newsweek: "We would expect [Greenland sharks] to have slow metabolisms, but how slow is certainly surprising and aligns well with research on the age of these sharks."

Previous research indicates that animals with slower metabolic rates have longer lifespans, while those with faster metabolic rates generally have shorter lifespans.

Raoult said the slow metabolic rate may explain the long lifespans of Greenland sharks "to some degree."

"Larger animals typically have longer lifespans but also higher resting metabolic rates, so Greenland sharks are an exception in that they are large but have extremely slow metabolisms," he said.

In the study, researchers said understanding the dietary requirements of Greenland sharks was important to understanding how the species might fare, as climate change leads to shifts in prey availability and food webs.

The Greenland shark population is decreasing and its Arctic habitat is warming faster than any other region on Earth.

Researchers said their energy requirements mean Greenland sharks can survive on very little food, but their future remains uncertain: "Climate change is affecting both the physical environment and biological communities of the Arctic, emphasizing the importance of deriving these types of data on the behavior and energetics of species such as the Greenland shark."

Raoult said: "In general [the study] outlines that these are very slow-growing species that are vulnerable to overharvesting, and climate change—with increasing temperatures that increase metabolic rates.

"On the other hand, they require very little food to meet their metabolic requirements, meaning that they only need a small population of fishes available to prey on to sustain themselves."

#SharkWeekNOAA Some sharks live for a very long time. Spiny dogfish are small but can live to be 100 years old. The Greenland shark has them beat with a...