TURTLES ARE AMAZING CREATURES
by Whit Gibbons
November 12, 2006
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.
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.
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.
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.
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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