Did you know that there are sharks with a tail fin as long as the body of the shark itself? The Common thresher uses the elongated upper lobe of its caudal fin as a whip-like weapon to stun its prey.
That happens both via shockwave (the whip slices through water as fast as 47 mph – 75 kph) – as shown in the video – and direct contact, explaining why most Common thresher caught by baited hooks were caught in the tail and not the jaw.
Common threshers live worldwide in tropical to cold-temperate seas both in coastal and oceanic waters in numerous isolated subpopulations. They live at least 24 years (maybe up to 50 years) and give birth to 2 to 7 living young (ovoviviparous) in special shallow nursery areas, after a gestation period of nine months, during which the embryos feed on a steady supply of unfertilized eggs (oophagy).
The diet of the Common thresher consists mostly of small schooling fishes, like mackerels or herrings, hopefully resulting in meat with lower amounts of methyl mercury than in most shark meat. Because worldwide Common threshers are intensely fished commercially for its highly prized meat, but also for its fins (according to DNA-tests at least 2-6% of the entire shark-fin trade), hide (for leather) and liver oil. This results in an IUCN-Red List Category of Vulnerable worldwide.
Additionally, the common thresher is one of the most important and prized species in recreational fisheries, due to putting up a strong, determined fight for its life (cause for few cases of thresher shark “attacks” of boats). Despite reaching up to 6 m -20 ft- in length, Common threshers are rather shy and no danger to humans.
Like its relatives, the mackerel sharks (for instance the salmon shark), Common threshers are able to elevate their body temperature above that of the surrounding water using counter-current heat exchangers.
Their other name fox shark as well as their scientific name (Alopias vulpinus) date back to the Greek philosopher Aristotle. He described “clever” (albeit false) behaviors of the Common thresher, leading to the fox analogy – not their tail.