Thresher Sharks are named for their exceptionally long, thresher-like tail (which can be as long as the total body length). Thresher sharks are active predators and use their tails as a weapon to stun prey. It has a short head, cone-shaped nose. The bigeye thresher found here at Malapascua, Philippines can reach a length of 4.9 m (16 ft.). The thresher in this video has a body of approximately 6 ft plus a tail for a total of 12 ft.
Divers only view the threshers at Malapascua in the morning. They come up from deep water during the night to cleaning stations then return to the deep water after the sun comes up. The dive boats leave at 5 am to travel the 40-minute journey out to the cleaning stations.
Many thanks to Wilbert Arriesgado, our dive guide for the week at Thresher Shark Divers, for his expert advice and keen eye.
The thresher shark or Alopias pelagicus is a type of mackerel shark. The threshers grow up to a length of 5-6 meters, about half of which is the huge scythe-like tail for which it is named.
Thresher sharks normally live in deep water, are nocturnal (night creatures) and therefore are not often seen by divers. Thresher sharks are found occasionally in other locations. But in Malapascua, you can see them regularly. They have huge eyes to see in the dark. Also, they have tiny, sharp teeth. Thresher Sharks eat squid and schooling fish like herring and mackerel. Also, they use their tails to “corral” the fish into denser schools. Their tail is also used to stun the fish. Additionally, they sometimes “breach” and can jump out of the water.
Why are they here?
Monad Shoal near Malapascua is a sunken island at a depth of 16-32m whose sides drop off to 230m. The thresher sharks live and hunt in this deep water mostly, but in the early morning, they come up to the Monad Shoal before it gets too light. Its cleaning stations attract the sharks. They have a symbiotic relationship with the small fish called cleaning wrasse. The wrasse eats dead skin and bacteria from the shark’s body, gills, and inside its mouth. The sharks would never think of eating the wrasse because of the cleaning benefits to these huge animals. The cleaning stations are like a car wash for fish!