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Common Thresher Sharks

The common thresher shark, despite its name, is not common at all. In fact the International Union for the Protection of Nature has classed it as "vulnerable" on the "Red List of Endangered Species." Numbers are steadily declining, primarily due to human activity.

Habitat
- Common threshers are adaptable, inhabiting both coastal regions and the open oceans. It lives throughout the world's oceans, except near the poles, in seas ranging from tropical to cold, but appear best adapted to mild, temperate waters. Catches show these sharks swim at depths of 1,200 feet or more, and are most often caught at around 500 to 600 feet.
Physical Characteristics
- The most striking feature of thresher sharks is the enormous tail. The common thresher has a greatly extended top part of the tail, which is often longer than the shark's body. It is not certain as of the date of publication exactly what the main function of the extended tail is. Thresher sharks have been observed using their tails to hit, and render immobile or unconscious, prey animals, which are mainly fish. The tails may also have a defense purpose. Otherwise, the sharks are fairly typical ocean sharks with streamlined bodies and relatively small teeth. With a maximum length of at least 18 feet, they are among the larger species of shark.
Behavior and Reproduction
- These are live-bearing sharks that only give birth to a few pups at a time, usually just two. The young sharks seem to stay relatively close to the coast for their first few years. This species is slow to grow and mature, although individuals can live to at least 24 years of age. This makes thresher sharks vulnerable to over-exploitation. As with many other sharks, sharks form gender-segregated groups, possibly because of the differing needs of males and females.
Issues
- Thresher sharks are heavily hunted. Their fins, meat and skins are all valuable. As a result, thresher shark populations have seen a sharp decline since the latter part of the 20th century. They are under threat indirectly from other human activities, for example from the overfishing of prey fish and water pollution. Thresher sharks are also caught accidentally as bycatch. As far as threats from the sharks to humans, there are no confirmed reports of any fatal attacks from this species.

Animals & Science