DO TURTLES GO IN THE WINTER?
by Whit Gibbons
March 11, 2007
change could potentially turn late winter into early spring, but winter
is officially here for several more days, until the spring equinox on
March 21. So, a question from Florida still qualifies as a wintertime
do turtles go when it's cold? I just read an article about someone in
Brandon, Fla., who brought their pet baby turtles inside and put them
in the bathtub to protect them during a cold snap. The story focused on
the pet golden retriever that ate one of the turtles and was taken to
the vet. I don't actually care what happens to turtles eaten by dogs but
want to know if cold is really a problem for turtles in the wild--freshwater
turtles, sea turtles, tortoises?
is not a "problem" under natural conditions for native animals
or plants. Individuals unable to tolerate seasonal changes in temperature
under natural conditions are typically eliminated through natural selection.
Thus, the genetic makeup of future populations is determined by the survivors,
individuals who could withstand a cold climate. Ancestors of all turtles
on earth today survived whatever natural conditions of cold they were
confronted with. But what do they do when no one is around to put them
in a bathtub for the dog to eat?
living in the temperate zone deals with winter's cold. Birds fly south
as winter approaches. Mammals add a layer of body fat when cold weather
arrives. Trees lose their leaves before they freeze. Turtles, likewise,
have their own special ways of dealing with winter.
to the turtles you saw basking on logs or rocks in the sun during spring,
summer, and fall, that then disappeared when it got cold? At body temperatures
of about 40 to 50 degrees F, most reptiles become sluggish, stop eating,
and seek hiding places to get safely through the winter. But turtles are
air-breathing animals with lungs, so can they live out the winter underwater?
turtles go into the mud or under the bank where the water is cold but
does not freeze. An advantage most reptiles have over many mammals and
birds is that their metabolism drops with their body temperature, meaning
that they require less oxygen. Some turtles can stay underwater for days
without taking a breath, as long as the water stays cold. Many species
actually absorb oxygen from the water through tissues in the throat and
the world's tortoises live in warm climates, but the gopher tortoises
of the Southeast have an unusual strategy for escaping cold winters. They
retreat into underground burrows that serve as natural caves for protection
from cold and predators. Gopher tortoises dig the burrows, which are often
more than 20 feet long. In South Carolina, Georgia, and northern Florida,
gopher tortoises may stay underground for days or weeks at a time until
warm weather returns.
Most sea turtles have a different approach to dealing with winter. They
simply do not live where it is cold. Loggerhead and green sea turtles
commonly lay their eggs on beaches of Florida and even into Georgia and
the Carolinas, but this is characteristically in the early summer. And
hatchling sea turtles normally crawl to the sea in late summer, before
the Atlantic waters of the Southeast become frigid. So, most sea turtles
spend time in the temperate zones only during the warm seasons.
in biology, we can expect an exception. The world's largest turtle, the
leatherback, nests in the tropics but actually travels into the Arctic
Ocean during the summer. According to Jim Spotila's book, Sea Turtles:
A Complete Guide to Their Biology, Behavior, and Conservation (Johns Hopkins
University Press, 2004), the giant leatherback sea turtles use a variety
of mechanisms to stay warm even in icy waters. These include, a thick
layer of body fat for insulation, blood vessels in their fins that replace
cold blood with warmer blood, and a big body that loses heat slowly.
I checked into the Florida "dog eats turtle" story. Worry not.
Both dog and turtle are safe after a little operation at the vet's. Both
are probably hoping Florida doesn't have any more cold snaps this year.
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