Thanks to a cold environment, which causes a slow metabolism, bowhead whales (Balaena mysticetus) can live for more than 200 years - nearly 3 times longer than the average human, making it the longest-lived mammal.

Bowhead whales can grow 14 to 18 m (46 to 59 ft) in length, and unlike most whales, they lack a dorsal fin. This thick-bodied species can weigh from 75 to 100 tonnes (82 to 110 US tons). They live entirely in fertile Arctic and sub-Arctic waters, unlike other whales that migrate to low latitude waters to feed or reproduce. The bowhead also has the largest mouth of any animal.

Of course, following around a whale to measure how long it lives is practically impossible. Researchers discovered this amazing feature in 2007, when a 15 m ...