The sleeper sharks apparent short comings have helped them adapt to sneak up on their slumbering seal prey.
Greenland sharks, also called sleeper sharks, are known to consume ringed seals, harbor seals, hooded seals, and bearded seals. Marine biologists originally thought the sharks fed on the carcasses of dead seals, but fresh seal chunks found in sharks' digestive system as well as bite wounds on living seals showed that the sharks were eating live seals.
In a recent study on Greenland sharks' speed, published in the Journal of Experimental Marine Biology and Ecology
, researchers found that the sleeping habits of arctic seals sleep leave them vulnerable to the slow moving sleeper shark. Arctic seals sleep in the water to avoid being eaten by polar bears.
Sleeper sharks cruise at speeds of 3/4 miles per hour. Reaching lengths up to 30-feet, sleeper sharks are the slowest moving relative to their size across fish species. It is thought that they may be super slow because the water around them averages only about 36 degrees F.
In addition to their speed issues, Sleeper Sharks often have poor vision, this is because of parasite copepods that eat away at their corneal tissue. However, they have developed an astounding sense of smell which is thought to make up for their short sightedness.