by Whit Gibbons

November 12, 2006

The eastern mud turtle is one of my favorite turtles, in part because of its ecological message. We are constantly bombarded with environmental issues about habitat destruction, the decline of species, and the need to put one species or another on an environmental welfare program. Occasionally, it is pleasant to consider that some of our native species, such as mud turtles, are doing well most places where they occur.

At the Savannah River Ecology Laboratory (SREL), we have studied mud turtles on the U.S. Department of Energy's Savannah River Site (SRS) in South Carolina for many years. "We" includes Judy Greene, who has been the research coordinator of the project. I myself began studies on mud turtles more than 35 years ago. Fortunately for our plans to conduct a long-term study, mud turtles live a long time. To put their longevity into perspective compared to other wildlife, white-tail deer may go through a couple of generations before a baby mud turtle reaches adulthood. Based on the capture of particular specimens on the SRS, we know that many mud turtles live under natural conditions for 20 years or more.

In the past five years, University of Georgia graduate students at SREL have caught mud turtles on the SRS that we know hatched from their eggs years before the students were born! These are typical grad students, not child prodigies, so these turtles are unquestionably more than a quarter of a century old. Some of these mud turtles were adults the first time we met, so they are now clearly senior citizens of the reptile world. The oldest one we know of so far is an adult female captured in 1975 when it was at least seven years old and then released into the aquatic habitat it called home. Judy recaptured it in 1997--22 years later.

We can tell when we have previously captured a particular turtle because we give each an individual code. With a file, we notch three or four of the numerous scales around the edge of the shell. These identification marks do not hurt the turtle, but they leave a nick in the shell that is recognizable years later. The pattern of notches serves as a signature used to distinguish an individual from all others in the population.

Known as mark-recapture by research ecologists, the technique provides valuable information about animals. By capturing them, taking appropriate measurements, and then tagging or marking them for future identification before releasing them where they were found, we learn about the animals' ecology, such as how far they move, how fast they grow, and how old they get. The female mud turtle mentioned above had grown less than inch over 22 years and was within 100 feet of where it had been more than two decades earlier. Protection of mud turtles' freshwater wetland habitat is the essential ingredient in their continued survival.

Eastern mud turtles, one of the smallest turtles in the country, seldom reach a length of five inches. An adult looks like a black paperweight with legs. The babies look like black pecan shells with bright red or yellow undersides. No one knows why a baby's belly is brightly colored. Perhaps the color signal makes predators cautious about eating them. The very name, mud turtle, makes a statement about its less-than-spectacular coloring.

Adult mud turtles spend much of their life on land, where they must have protective measures other than camouflage. They rival box turtles in their ability to slam shut both ends of the hinged lower shell, making it difficult for foxes to make a meal of them. Like many animals and plants, the lifestyle and habits of mud turtles are not readily revealed in a terrarium or a chance meeting alongside a lake. But anyone who spends time getting to know mud turtles begins to like them.

Mud turtles vary little in appearance from New England to Mexico. And even with long-term studies like those at SREL, the ecology of most species is still poorly understood. Mud turtles keep a low profile, but they are an integral part of natural systems. And they are a symbol that some parts of our North American natural heritage are doing fine.

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