Australia's Cannibal Sharks

Video highlights from Australia's Deadliest: Shark Coast

Surprising data from a tag tracking a great white shark off of Australia could be evidence of cannibalism.

In 2014, a research tag that belonged to a great white shark, was found four kilometres away from where it had been affixed to the shark.

The tag, initially attached in November 2003 off southwestern Australia, was set to record ambient temperatures and depth. Its data showed that four months after it was attached, the female great white abruptly dove to a depth of 580 metres. The ambient temperature surrounding the tag spiked from 8°C to 26°C. The data suggested an attack.

Filmmaker David Riggs, who'd been hired to document the tagging project that involved the nine-foot-long female shark, couldn't believe the data at first.

Clearly something ate the shark, Riggs said in a YouTube clip uploaded by the Smithsonian Channel. But "what could kill a three-meter great white?" Riggs asked.

A great white shark cruises off the Australian coast. [Photograph by Fred Bavendam, Minden/Corbis]

Cannibalism Is Common

Experts say that speculation that a great white devoured the missing female great white is not outside the realm of possibility.

"Cannibalism in sharks is quite common in both juveniles and adults," said Camrin Braun, a doctoral student at the Woods Hole Oceanographic Institution in Massachusetts who studies shark population and behavior. White sharks in particular have highly variable diets, he added in an email interview, and are likely opportunistic when it comes to finding food.

But a more likely explanation for the surprising tagging data, said Braun, is that the female great white got caught in the crosshairs of a killer whale.

The only other animal that could take on a small great white—and that has a warmer ambient internal temperature—is the killer whale, Braun said. Their internal temperatures run about 32°C, he explained. "Thus, it seems likely that a feeding killer whale that is ingesting cold seawater and food could easily have a stomach temperature of 25.5°C."

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