Thresher sharks slap fish to death, according to a new study that adds sharks to the list of ocean predators that can kill with just a slap.

For this latest study, published in PLoS ONE, Simon Oliver of the Thresher Shark Research and Conservation Project and his colleagues observed thresher sharks hunting schooling sardines. The action took place in the waters off of a small coral island in the Philippines.

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Using handheld video cameras, suggesting that they were very close to the sharks, Oliver and his team recorded 25 instances where the sharks slapped their tails on or very near fish. The slaps either killed the sardines outright or stunned the fish so that the shark could easily gulp them down.

Thresher sharks initiated the behavior by drawing their pectoral fins inward to lift their posteriors rapidly. The forceful tail slapping followed. Slaps were so hard that they dissolved gases that bubbled out of the water.

The sharks ate an average of 3.5 sardines after each successful hunting event.

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Clearly this method works, and it’s more efficient than hunting fish one by one. Sardines are on the small side, so a predator could quickly run out of steam trying to chase a single fish, and then another and another.

Most fish species are on the decline, due to overfishing, pollution and other human-caused problems, so the hunting method is increasingly important for sharks.

“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,” said Oliver in a press release.

The tail slaps might also help sharks to communicate with each other, although that hasn’t been proven yet. Humpback and sperm whales slap their tails a lot, turning them into a sort of oceanic Morse code to communicate over long distances.

Photo: A Bigeye thresher shark swims near Cocos Island National Park in Costa Rica.