Pelagic thresher sharks use tail-slaps as a hunting strategy, according to a new study reported in the open-access journal PLoS ONE.
Thresher shark at Malapascua Island, the Philippines (Petter Lindgren / CC BY-SA 3.0)
The pelagic thresher (Alopias pelagicus) is a species of shark characterized by the greatly elongated upper lobes of their caudal fins. They typically measure about 10 feet (3 m) long.
Between June and October 2010, study lead author Dr Simon Oliver from the Thresher Shark Research and Conservation Project and his colleagues filmed thresher shark activity with handheld video cameras in the waters off a small coral island in the Philippines.
They observed that thresher sharks hunted schooling sardines by rapidly slapping their tails hard enough to stun or kill several of the smaller fish at once. In total, the biologists recorded and analyzed 25 instances of tail-slapping to stun prey.
Thresher sharks seemed to initiate the behavior by drawing their pectoral fins inward to lift their posteriors rapidly, followed by tail-slapping forceful enough to stun or kill several prey, and even cause dissolved gases to bubble out of the water. After a successful hunting event, sharks ate an average of 3.5 sardines.
A sequence of still images taken from an overhead tail-slap hunting event (Oliver SP et al)
For large marine predators, being able to stun more than one prey at a time is likely to be a more efficient means to hunt than chasing after many small fish in a school. Dolphins and killer whales are known to use tail-slaps to control or stun prey, while humpback and sperm whales use tail-slaps to communicate over long distances.
“This extraordinary story highlights the diversity of shark hunting strategies in an ocean where top predators are forced to adapt to the complex evasion behaviors of their ever declining prey,” Dr Oliver said.
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Bibliographic information: Oliver SP et al. 2013. Thresher Sharks Use Tail-Slaps as a Hunting Strategy. PLoS ONE 8(7): e67380. doi:10.1371/journal.pone.0067380
