Lazy Greenland sharks ‘feed on sleeping seals’

Scientists have suggested that Greenland sharks may feed on sleeping seals as their super-slow swimming speed can nowhere near match that of its swift prey. While seals swim at around 3mph, the notoriously sluggish sharks only average around 1mph, making them the slowest fish in the ocean relative to their size.

The sharks in the waters off Svarlbard were tagged by researchers from National Institute of Polar Research in Tokyo in an attempt to figure out what had been killing seals in the area. It was originally thought that Greenland sharks must only be eating dead seals, but the results of the study suggest otherwise.

Yuuki Watanabe, who took part in the data-tagging survey, explained how scientists had been baffled when seal remains were found in the stomachs of Greenland sharks. “It was hard to understand,” he told BBC Nature, “because [it would seem] impossible for them to catch fast-swimming seals.”

It is thought that the sharks swim so slowly due to the energy expended in keeping the body temperature up in waters that average around 2°C. The researchers, therefore, believe that the dawdling fish “sneaks up” on seals as they sleep in the water – a precaution the seals take to protect themselves from polar bear attacks on land.

Vincent Gallucci, a shark expert from the University of Washington, said the lazy sharks don’t even need to get the whole of the prey into their mouths to eat it. “It can get an assist from a sucking action as part of its feeding process,” he told BBC Nature.”This does make it a bit easier for a lie in wait ambush predator to consume prey that pass near its mouth.”