One of the easiest sharks to identify underwater — thanks to its huge tail — the thresher shark is on many divers’ bucket lists. But why is that tail so long anyway?
What is a thresher shark?
The thresher shark family includes three documented species as of today: the bigeye thresher; pelagic thresher; and common thresher. Their genus and family name are derived from the Greek alopex, meaning fox. In several languages, including French, they are known as a fox shark.
The pelagic thresher is the smallest of the species, with a length of around 10 feet (3 m). The common thresher can reach up to 20 feet (6 m) long — tail included. It can be hard to distinguish the species, but a color difference is common: pelagic thresher sharks tend to be blue, while the common thresher shark tends to look dark green and bigeyes tend to be brown. The size is also an indication of the species.
Their famously long tail, or caudal fin, can make up half of their length. These solitary sharks hunt alone and use their tail as a weapon to stun their prey, making them efficient predators. They feed mainly on schooling fish where their tail is very effective, such as tuna or mackerel. Threshers also use their tail as a propeller, which they use to jump out of the water, as very few species of sharks do.
Their reproduction cycle is slow, as adults do not mature until 8 to 14 years old depending on the species. Females give birth to two to four pups that are born at around 5 feet long (1.5 m).
Where can you find them?
They live mainly in open oceans and in deep waters. You’ll find pelagic and bigeye thresher sharks in the Indo-Pacific, while you can also find the common thresher in more temperate waters. Popular spots to dive with them include the Philippines, California, Indonesia, Micronesia, Egypt, and the Galapagos.
How should you behave around them?
As of today, there is only one ever recorded attack on a diver. Thresher sharks are shy underwater and do not seek human interaction. As with all marine animals, do not intrude upon or corner them.
What is their conservation status?
Thresher sharks are listed as vulnerable to extinction on the IUCN Red List. Main threats are fishing (bycatch) or commercial fishing for fin trade, meat, or their skin.