The great white shark

A powerful predator, the great white inspires fear. This awesome shark grows to over 6m (20 ft) long and weighs more than 2 tonnes (2.2 tons). It is the largest of the predatory sharks, capable of eating seals whole. The great white became famous in the Jaws movies where it appeared as a blood-thirsty creature intent on killing people. Attacks on people are rare, and possibly occur when a shark mistakes a person for its usual seal prey. Despite its fame, little is known about the great white because it is rarely seen. Scientists have yet to discover where mating and birth occur, and their age when they reproduce or die. No one knows how many great whites there are, but in some areas they may be on the decline.

Warm blood Creat whites and their relatives - the mako, thresher, and porbeagle - are all warm-blooded, which means that they are able to keep their body temperature higher than the surrounding water. Only mammals, birds, and a few fast fish, like tuna, are warm-blooded. These sharks have blood vessels in their muscles arranged in complex nets, so that the warm blood leaving the muscles passes heat the the cold blood coming from the gills. A high body temperature means that great whites have warm muscles which are able to act fast. This is important for a predator that has to make a high-speed dash to catch its prey. Being warm-blooded may also help the great white to digest its food more quickly. Scientists estimate that after a big feed a great white can last three months before needing another meal.