Animals

First Known Incidents of Alligators Eating Sharks Reported in Southeastern US

The findings will help wildlife biologists develop better population models and strategies for protecting endangered species.

Once a writhing alligator is hauled aboard — large, adult males range between 11 and 16 feet in length — Nifong and his fellow researchers strap it to a board, prop its mouth open with a wide circle of plastic or steel pipe, feed a hose down its throat, fill its stomach with water, and then “jiggle” the animal’s belly around until it pukes up its lunch.

Nifong’s research specialty is the eating habits of the American alligator (Alligator mississippiensis), the toothy alpha predator that inhabits much of the southeastern United States along the Atlantic and Gulf Coasts. While coastal-dwelling alligators are known to chow down on small fish, crustaceans, and unsuspecting birds, they’re also opportunistic eaters. Over the past few years, Nifong’s been trying to figure out if one particular rumor is true: Do alligators really eat sharks?

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Stories have circulated for ages about deadly encounters between gators and sharks. A magazine article from 1877 in The Fishing Gazette describes an epic battle between roughly 500 alligators and untold hundreds of sharks along the coast of Jupiter, Florida. The gators gorged themselves on a school of fish trapped by a flood tide and nearby sharks were attracted by the carnage. An eyewitness described the scene: “…[the] sharks and alligators rise on the crest of the waves and fight like dogs.”

But apart from these anecdotal accounts, there was no solid proof — photos or video with exact dates and times of an event — that alligators indeed ate sharks, or vice versa.

So Nifong set out to find some.

Searching through alligator puke wasn’t likely to uncover many clues, since alligators fully digest their prey in one to three days. And even if alligators did eat sharks, it was probably a rare enough occurrence that it would take extremely good luck to capture a gator and pump its stomach within a day of eating a shark.

So Nifong cast his net wider, asking colleagues, friends, and friends of friends if they’d ever personally witnessed an alligator eating a shark or ray, both members of the Elasmobranchii family. He found a sea turtle researcher who had twice documented alligators (1997 and 1999) feeding on sharks on Wassaw Island, Georgia — but there weren’t any pictures. Darn.

But then he hit paydirt. In 2003, a US Fish and Wildlife Service staffer working in the Ding Darling National Wildlife Refuge in Sanibel, Florida, had actually photographed an eight-foot alligator attacking and engulfing a three-foot nurse shark. Here was the proof!

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In a recent article in the journal Southeastern Naturalist, Nifong and co-author Russell Lowers, a wildlife biologist at the Kennedy Space Center, documented seven separate encounters, recorded and in some cases photographed by field researchers, where an alligator had indeed eaten a shark or ray.

Why was this so important to prove? Because many species of sharks and rays use protected coastal estuaries and tidal rivers as nurseries for their young. And those are exactly the types of brackish environments where the seven alligator attacks were documented.

“It’s really important to figure out if the juvenile sharks and rays are getting nailed by these predators and to account for that in population models,” Nifong told Seeker.

Of the four shark and ray species observed in the documented attacks — nurse sharks, lemon sharks, bonnethead sharks, and Atlantic stingrays — none were endangered. But Nifong noted that the smalltooth sawfish, which is seriously endangered, lives in the same waters as that nurse shark gobbled up in Florida, and it’s also in the Elasmobranchii family.

It’s no surprise that alligators, sharks, and rays would find themselves in the same waters. Even though alligators primarily stick to freshwater and Elasmobranchii are ocean dwellers, both can handle waters ranging in salinity from 10 to 15 parts per thousand up to full strength seawater (36 ppt). The attack in Georgia, for example, happened right off the beach in pure ocean water.

Alligators lack salt glands to help regulate their body’s salinity, so long-term exposure to high-salinity waters will cause them to dehydrate, but Nifong said that he’s tracked alligators with GPS who regularly “commute” into ocean water for a “seafood buffet” before heading home to freshwater. Alligators will also drink freshwater during a rainstorm to stay hydrated in salty water.

“I’ve seen them standing with their mouth open in the marsh in the rain drinking the rainwater,” Nifong said, “as well as sipping off the top of the water column after it rained.”

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Proving that alligators eat sharks and rays is only the first step, explained Nifong.

Researchers still don’t know how many alligators eat how many sharks and rays, where they eat them, or what species are most prone to attack. But for biologists tracking the survival of endangered Elasmobranchii species around the world, it’s worth keeping an eye on those alligators.

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