Posted by: The ocean update | February 12, 2016

White shark’s diet may include biggest fish of all: whale shark

Image Source/REX/Shutterstock

Image Source/REX/Shutterstock

February 12th, 2016. Great white sharks are voracious predators, and it seems they even set their sights on the biggest fish in the sea. Two vertebrae recovered from the stomach of a 4.5-metre-long white shark caught 50 years ago show that it had been feeding on a whale shark, and a big one at that. It was around 8.5 metres long, the size of the vertebrae suggests (see image below).

Michael Newbrey at Columbus State University in Georgia, who identified the bones, says that juvenile whale sharks sometimes fall prey to other sharks. There have been unconfirmed reports of white sharks attacking sub-adult whale sharks, he says, but this is the first good evidence that adults might be targeted as well.

He is not surprised, though, to find bits of a full-sized whale shark in a white shark’s belly. “White sharks will chew just about anything they can get in their mouths,” he says. And their serrated teeth are well suited to cutting through flesh and skin.

What we don’t know is whether this white shark was attacking a live whale shark or feeding on a carcass. It was caught near a whaling station off the coast of Western Australia, where white sharks did scavenge on dead whales.

Gregory Skomal, head of the Massachusetts Shark Research Program, says his money would be on scavenging. “They’re well known for scavenging large whales, and I imagine they would also take advantage of other large dead fish,” he says.

And although they aren’t afraid to take on large animals like elephant seals or sea lions, white sharks tend not to target things much bigger than themselves, he adds. They also prefer to feed on the rich blubber of whales and seals, so whale sharks might be less appetising to them.

Either way, say both Newbrey and Skomal, the finding helps fill an important gap in our knowledge of what white sharks eat, which remains somewhat mysterious. “As long as we’ve been studying white sharks, we still don’t have a handle on what their diet is,” says Newbrey.

Fig. 1 a Whale shark Rhincodon typus. b White shark Carcharodon carcharias. c Two whale shark centra from a white shark stomach (Western Australian Museum, WAM accession P.29547-001)

Fig. 1 a Whale shark Rhincodon typus. b White shark Carcharodon carcharias. c Two whale shark centra from a white shark stomach (Western Australian Museum, WAM accession P.29547-001)

Citation : Whale shark on a white shark’s menu. G. I. Moore, M. G. Newbrey. Marine Biodiversity (Impact Factor: 1.1). 12/2015; DOI : 10.1007/s12526-015-0430-9

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