American alligators gobble up anything they can get their jaws around. Now, a new study has added new items to their menu: sharks and stingrays.

It's particularly surprising, says study leader James Nifong, an ecologist at Kansas State University, because alligators are known as freshwater predators.

In fact, when Nifong started asking alligator experts if they’d ever encountered instances of the toothy reptiles preying upon elasmobranchs—a group that includes sharks, rays, and skates—quite a few people thought he was joking. (Watch a big alligator eat a smaller one.)

Persistence paid off, however, and Nifong confirmed four separate instances in which an American alligator ate a lemon shark, a nurse shark, a bonnethead shark, and an Atlantic stingray.

He also uncovered some historical accounts of sharks preying upon American alligators, suggesting that the two carnivores square off more often than thought.

View Images An American alligator chows down on a nurse shark in Florida's J.N. "Ding" Darling National Wildlife Refuge. Photograph courtesy of U.S. Fish and Wildlife Service

Both "are known for their extreme eating habits, and both are highly opportunistic predators,” says Nifong, whose findings were published in the most recent issue of the peer-reviewed journal Southeastern Naturalist.

“So, when presented with a potential opportunity to feed, they are not likely to pass it up.”

Shark Vs. Gator

There are a few reasons why observations of shark-gator showdowns are scarce.

For starters, both animals are tough to follow and observe in their coastal habitats, says Adam Rosenblatt, an ecologist at the University of North Florida who studies alligators.

What's more, gators consume sharks that are quite a bit smaller than Jaws, and so the fish may look like just any other to the average onlooker. ("Watch: Alligators' Hunting Secrets Revealed by Crittercams.")

Still, alligator researchers have a method for examining the stomach contents of live alligators—a sort of cross between a stomach pump and the Heimlich maneuver—so shouldn’t there be more evidence of sharks in gator guts?

Probably not, says Rosenblatt, who is all too familiar with picking through alligator vomit.

“Most prey gators eat turn to mush pretty quickly within their stomachs,” he says. “It all turns into one big pile of indistinguishable stuff, except for certain body parts like hair and shells.”

Ancient Enemies

Elsewhere in the world, there are several observations of crocodilians—a group that includes alligators, crocodiles, and caimans—duking it out with elasmobranchs.

In Australia, people have witnessed saltwater crocodiles going into the surf to hunt bull sharks. Similarly, a study published earlier this year found that more than half of the freshwater sawfish sampled in Western Australia sported scars inflicted by freshwater crocodiles.

What is this jaguar stalking for its next meal?

And in South Africa, one Nile crocodile was found with the remains of two unidentified shark species in its belly. (Read "How Nile Crocodiles Are Bigger and Badder Than Alligators.")

There are even some crocodilian fossils that show bite marks from ancient sharks, hinting that these predators have been enemies since the Late Cretaceous period.

'Wild and Crazy' Place

Perhaps most interesting are the several accounts Nifong uncovered of sharks attacking large groups of alligators.

In the most bizarre instance, in 1877, hundreds of American alligators congregated in an inlet near Jupiter, Florida, attracted by fish trapped by the high tide. Hundreds of sharks, sensing potential prey, followed. In the days after the battle, beaches as far as 80 miles away were littered with carcasses of both species, according to The Fishing Gazette, a sports magazine at the time. (See a National Geographic interactive of sharks, lords of the sea.)

While these historical accounts were “definitely embellished”—probably to exaggerate the number and size of the animals involved—“the fact remains these were definitely observations of alligator-elasmobranch interactions," Nifong says.

Rosenblatt agrees: “Gators are known to congregate in large groups occasionally to feed on abundant prey, and sharks are known to do the same thing, so it's certainly possible that large-scale interactions would take place between the two."

He adds that both gator and shark populations are generally smaller than they once were, which could explain why such massive gatherings are rare today.