Alligators Eat Rocks to Increase Time Underwater

A crocodile in Cuba's Jardines de la Reina.

A crocodile in Cuba's Jardines de la Reina. Q Phia / Flickr

Alligators fill their bellies with small rocks as a way to stay underwater for longer periods of time, according to a recent study in the journal Integrative Organismal Biology. Ingesting stones equal to just 2.5 percent of the alligators’ body weight increased the animals’ dive time by an average of 88 percent, extending it up to 35 minutes, Science magazine reported.

Scientists have long known that alligators, crocodiles, and other crocodylians frequently consume rocks on accident while attacking live prey or on purpose as a source of minerals, to get rid of parasites, or to help digest difficult meals — a behavior also practiced by some birds. But the new study is the first time the conduct has been shown in lab experiments to affect the animals’ swimming.

Led by biologist T.J. Uriona and colleagues at the University of Utah, the study monitored juvenile American alligators on 21 dives before they voluntarily swallowed stones — also known as gastroliths — and on 21 dives after. The stones helped some animals increase their time underwater by as much as 117 percent, the additional weight allowing them to take more air into their lungs and still sink. The biologists now hope to study the behavior in adult alligators.