Alligators are Feasting on Sharks in America's Rivers and Estuaries, Scientists Discover

There is always a bigger fish, the old adage goes and if there isn’t, at the very least there is a bigger alligator, new research confirms.

Even when it comes to sharks—an infamous predator of the sea—as they risk becoming prey to the American alligator when they venture into freshwater, a study published in Southeastern Naturalist confirms.

The study of the stomach contents of 500 living alligators captured and examined by Kansas State University researcher James Nifong and IMSS wildlife biologist Russell Lowers unveiled four different species of sharks, including nurse sharks and stingrays.

The American alligator, also known as Alligator mississippiensis, and the various types of sharks usually swim in waters that rarely overlap as alligators are freshwater dwellers, while sharks top food chains in salt waters.

On the rare occasion where either species feels some wanderlust for the other’s ecosystem, the alligator is liable to swap its meal of crustaceans, snails, and smaller fish for more vicious prey.

gator-shark-sm American alligator preying on a nurse shark. U.S. Fish and Wildlife Service J.N. "Ding" Darling National Wildlife Refuge.

Sharks have been spotted slipping into freshwater areas on occasion. Equally, while alligators lack salt glands—a requirement if their body is to filter the saltwater they plan on surviving in—the species can suss out whenever saltwater becomes temporarily diluted, after heavy rainfall for example.

“Alligators seek out fresh water in high-salinity environments,” said Nifong in a statement. “When it rains really hard, they can actually sip fresh water off the surface of the saltwater. That can prolong the time they can stay in a saltwater environment.”

Alligators are not inherently the victor in an altercation with any shark, however. In fact, as the relationship between the two species becomes closer, what the dynamic between them looks like is more of mutual hunting or “reciprocal predation.” In other words, it is likely that once hungry and pitted in the same environment, it is a question of size that determines if the alligator eats the shark or vice versa.

“The frequency of one predator eating the other is really about size dynamic,” Nifong said “If a small shark swims by an alligator and the alligator feels like it can take the shark down, it will, but we also reviewed some old stories about larger sharks eating smaller alligators.”

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