TOKYO (JAPAN)- The Greenland shark has been titled the slowest shark of the world, not reaching more cruising speed than one mile per hour. Yet they feed on seals. Scientists think the sharks sneak up on seals that sleep under water.

The National Institute of Polar Research in Tokyo have measured the swimming speed of the ocean’s slowest shark. Its reputation was already known but its sluggishness surprised the scientists.

Previous research had revealed seal remains in the stomachs of the sharks.The study was done together with the Norwegian Polar Institute, to tag Greenland sharks in the waters off Svarlbard.

The study, published in the Journal of Experimental Marine Biology and Ecology, was the latest part of an ongoing mission by the Norwegian researchers to find out what has been killing the harbour seals off Svarlbard’s coast.

Greenland sharks
It was thought that Greenland sharks simply fed on the carcasses of dead seals on the seafloor, but the team recently discovered evidence that they were taking live seals.

Speed or no speed
The tagging study found that, while seals swim at about 1m per second (2mph/3km/h), the sharks’ maximum bursts of speed reached only 0.7m per second – far too slow to catch a swimming seal. The sharks’ speed might be limited by the energy costs of swimming in near-freezing water, which has an icy average of 2C (36F).

The energy cost of regulating their body temperature in the almost freezing depths could be the reason for the sharks’ very limited speed.

Read more at BBC Nature.

See the video of an ecounter with a Greenland shark: