Alligators, rulers of the swamps, link marine and freshwater ecosystems

The scientists used radio or GPS transmitters to track alligators adn discovered that the amount of time alligators spend in fresh or salt water depends on factors such as tide range and water temperature.

Carrying a GPS transmitter, an alligator swims in a tidal river near Sapelo Island, Georgia. Image credit: James Nifong/Kansas State University

Unlike their relatives the crocodiles, alligators don't have salt glands and therefore can't survive full-time in salt water. They move back and forth between marine and freshwater ecosystems to rebalance their salt levels -- and to feed.

The American alligator is the most abundant large predator in aquatic ecosystems along the U.S. Southeast coastal plain.

Historically, alligators have been considered a freshwater species due to their lack of salt-secreting glands. These glands allow their cousins, the crocodiles, to excrete excess salt from marine environments.

As a result, alligators' use of salty environments such as near-shore marine areas, mangrove swamps and salt marshes was, until recently, thought of as unusual behavior and of little ecological importance.

Since the late 1800s, however, alligators have often been spotted in salty environments in Southeast coastal areas.

By traveling from one ecosystem to another, alligators ferry nutrients like nitrogen and phosphorus from place to place in the food they eat and excrete.

By tracking 'gators, the ecologists determined that alligators remain in marine habitats for longer periods around spring tides -- tides just after a full or new moon, when there's the greatest difference between high and low water. (In contrast, neap tides occur just after the first or third quarters of the moon, when there is the least change between high and low water.)

Spring tides mean one thing for alligators: more food. Other factors also contribute to 'gator patterns of movement, such as temperature and precipitation, which are linked with their need to balance salt intake.

By understanding the factors that contribute to alligators' meanderings, environmental managers can gain a better understanding of alligators' place in coastal ecosystems. (NSF)

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