Australian researchers are hunting for what they call a "mystery sea monster" that devoured a 9-foot-long great white shark.
A tracking device previously planted on the shark was found washed up on a beach, and after analysis, it showed that it had suddenly undergone a rapid increase in temperature and a swift 1,900-foot (580-meter) dive beneath the waves.
Scientists attribute the more than 30-degree spike in temperature to the shark entering another animal's digestive system, and the unexpected plunge could be explained by the larger animal's rapid descent. Researchers found the tracking device about 2½ miles from where the shark was tagged.
The perplexing situation, which occurred four months after researchers tagged the shark, is chronicled in the Smithsonian Institute's documentary film "Hunt for the Super Predator," which airs in the United States on June 25.
"When I was first told about the data that came back from the tag that was on the shark, I was absolutely blown away," filmmaker Dave Riggs says in the documentary.
"The question that not only came to my mind but everyone's mind who was involved was, 'What did that?' It was obviously eaten. What's going to eat a shark that big? What could kill a 3-meter (9-foot) great white?"
Additional study of sharks in the area provided a possible answer to this question: According to researchers, larger great white sharks were found in the spot where the original shark met its fate.
These huge sharks, the scientists say, are big enough to have eaten another great white and are able to dive at the speed and depth observed by the tracking device.
It's not unprecedented for sharks to eat other sharks, and the researchers posit that a 2-ton "colossal cannibal great white shark" is a likely culprit in this case.