Thresher sharks use their tails like bullwhips to kill or stun prey

Film shot by diver is the first to show thresher sharks using their tails like a whip to hunt fish in the wild
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Link to video: Thresher shark whips sardines to death

A diver has captured rare footage of the unique hunting style of thresher sharks in tropical waters off the Philippines.

The film was shot near coral reefs that fringe the tiny Pescador Island where huge shoals of sardines draw sharks to the area.


The strikes were filmed by Klemens Gann, an underwater videographer and diving instructor, and analysed by marine biologists in the Philippines and the UK. The hunting strategy was seen in males and females of all ages.

The scientists studied 25 attacks on shoals of sardines between June and October 2010. Of these, 22 whipped their flexible tails over their heads. In the rest, the sharks flicked their tails sideways.

After each attack, the sharks swam round in a gentle arc and returned to the spot to snaffle the stunned and dead sardines.

Captured on handheld cameras in waters 10 to 25 metres deep, the film is thought to be the first to show thresher sharks using their tails to hunt in the wild. The sharks in the footage are "pelagic" or "open water" threshers, one of three species of thresher shark.

Marine biologists had long suspected that threshers used their tails to help capture their prey. Half of their body length is made up of a scythe-like tail. Pelagic threshers grow to nearly four metres long, around two metres of which is tail. Other adult threshers reach six metres long.

Simon Oliver, a marine biologist at the Thresher Shark Research and Conservation Project in the Philippines, said the sharks' "tail slaps" reached a speed of 24 metres per second, or more than 50mph. In some cases the strikes caused such a rapid pressure drop behind the tail that bubbles appeared in the water.

The physical force of the strikes killed and maimed some fish, but others were effectively knocked out by the pressure wave created in the attack.

"These overhead tail slaps cause explosive shockwaves in the water that we think are part of the hunting mechanism," Oliver told the Guardian.

Analysis of the overhead tail strikes showed they were successful only half the time. But when they did work, the sharks killed up to seven fish at once, either in the initial attack, or swiftly after as they lay stunned in the water. Details of the study appear in the journal PLOS ONE.

Threshers are not the only marine predators to use tail-slaps. Humpback and sperm whales slap the surface of the water to communicate over great distances, and killer whales have been recorded slapping shoals with enough ferocity to leave fish stunned. White sharks slap the water with their tail too, often as a warning to competitors.

Understanding how thresher sharks feed will help with efforts to protect them, Oliver said. Populations have fallen around 75% in the past decade, after being targeted by fisheries for their meat, or being taken as bycatch by sardine fisheries.

"This is a vulnerable species and if we understand how they use their habitats, we can go about managing and protecting them more effectively," Oliver said.

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