Shark-Eat-Shark: Are Great White Sharks Cannibals?

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A "colossal cannibal great white shark" made headlines this week after it supposedly gulped down a 9-foot great white shark as though it were a steak dinner, but the jury is still out and many experts believe that great whites are pickier eaters than most people might think.

The colossal cannibal theory is posited in the forthcoming documentary film "Hunt for the Super Predator," which airs in the United States on June 25. In the film, researchers find a tracking device that had previously been planted on the 9-foot-long great white. The device washed up on an Australian beach, and recorded that it had undergone a 30-degree spike in temperature before plunging down 1,900 feet in the ocean.

The heat could have resulted from the shark (and tracking device) going into another animal's digestive system before the hunter nose-dived into the watery depths, filmmaker Dave Riggs explained, adding that large great white sharks were later spotted where the possible fatal plunge took place.

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The great white eats great white shark tale has since gone viral.

"I too have heard portions of the 'white shark cannibalism' story in the popular press and over the radio," John McCosker, chair of aquatic biology at the California Academy of Sciences, told Discovery News.

"I don't hold much stock in anything that I have heard, and suspect that there is a more reasonable explanation," he added.

Thus far, the only direct evidence appears to be the missing shark, the rogue tag, its data, and the presence of other sharks in the area. If this incident involved people, the accused could not be convicted. Even the fate of the 9-footer is unclear. If the shark did become another animal's supper, orcas also live in Australian waters and have been filmed feasting on great whites. In other words, killer whales can kill killer sharks.

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It's true that great white sharks have been documented practicing cannibalism, but this occurs primarily before birth.

"Great whites come out fighting; they are born well developed and must fend for themselves from day one," Stephen Wroe, a senior research fellow in the University of New South Wales' Evolution & Ecology Research Center, told Discovery News.

Wroe added that "intrauterine (pre-birth) cannibalism is practiced by white shark pups, and it is likely that any white shark that makes it into the big wide world has already eaten one or more of its siblings. It's a hard life!"