Background for Teachers
TPW Magazine, June 2009
"It's not easy being green" may have been sung by a frog, but turtles could sing this, too! Despite their hard shell, turtles are tasty prey and also subject to changes in the environment around them. Turtles are pretty amazing, however, and have survived quite a few hurdles. Turtles are one of the oldest reptiles on earth.
Reptiles are "cold-blooded" air-breathing vertebrates. A tough leathery skin that has embedded scales covers their body. Most reptiles lay eggs, though some give birth to fully-formed young. This group includes crocodiles, alligators, turtles, snakes, lizards, and tuatara.
The top of a turtle shell is called the carapace and the underside is the plastron. The "scales" on the shell are called scutes. Contray to cartoons portrayals, turtles cannot jump out of their shells. The shell is a part of the body, attached to the leg, neck and tail skin.
From the TPWD booklet Texas Turtles:
An Introduction to Texas Turtles
Turtle, tortoise or terrapin? Many people get confused by these terms, often using them interchangeably. Texas has a single species of tortoise, the Texas tortoise (Gopherus berlanderi) and a single species of terrapin, the diamondback terrapin (Malaclemys terrapin). All of the remaining 28 species of the order Testudines found in Texas are called “turtles,” although some like the box turtles (Terrapene spp.) are highly terrestrial others are found only in marine (saltwater) settings. In some countries such as Great Britain or Australia, these terms are very specific and relate to the habit or habitat of the animal; in North America they are denoted using these definitions.
- Turtle: an aquatic or semi-aquatic animal with webbed feet.
- Tortoise: a terrestrial animal with clubbed feet, domed shell and generally inhabiting warmer regions.
Whatever we call them, these animals are a unique tie to a period of earth’s history all but lost in the living world. Turtles are some of the oldest reptilian species on the earth, virtually unchanged in 200 million years or more! These slow-moving, toothless, egg-laying creatures date back to the dinosaurs and still retain traits they used to survive then. Although many turtles spend most of their lives in water, they are air-breathing animals and must come to the surface to breathe.
If they spend all this time in water, why do we see them on logs, rocks and the shoreline so often? Unlike birds and mammals, turtles are ectothermic, or cold-blooded, meaning they rely on the temperature around them to regulate their body temperature. Basking on a log or rock is a convenient way for them to warm their bodies. Like most ectothermic animals, they do not tolerate radical temperature swings well.
So Why is Texas Home to So Many Turtles?
As with other animal and plant groups found in Texas, our diverse geography, topography and geology has contributed to the diversity in this group. Some of the species found in Texas occupy a very limited range consisting of one or more river drainages. Others, like the ornate box turtle (Terrapene ornata) or red-eared slider (Trachemys scripta elegans) are much more widespread, being found over most of the state. The limiting factor with turtles is usually water, so in West Texas these animals may be found only in the river bottoms, while in East Texas, where rivers are more common, they will be more dispersed.
Generally, turtle distribution in Texas is based on watersheds. Range maps of some species look surprisingly like a river map. These species, like the Cagle’s map turtle (Graptemys caglei) or the Ouachita map turtle (Graptemys ouachitensis) are often more adversely impacted by changes in habitat quality than are the more widespread species.
General Turtle Life History
All turtles are egg layers. Females may travel great distances over land in search of suitable soil or leaf litter in which to lay their eggs. Nest sites are often on a sunny slope where the eggs and young, which are not cared for by the mother, can be warmed readily by the sun. Turtle eggs are generally spherical to elongated with shells of varying degrees of hardness. Even in the nest, temperature can play a vital role in the life of the turtle. Studies have shown that with several species, temperature in the nest will determine the dominant gender of the young – warm nests produced primarily female turtles, while cooler nests produced primarily male young.
Eggs and young turtles are eagerly sought prey species for many animals, resulting in most of the young being eaten by birds, raccoons, skunks, mink, coyotes, dogs, and even people. Thus, a large number of eggs does not guarantee the survival of the species, nor of a specific genetic line. It also means that some of our turtles, even though they are producing a lot of young, can be very vulnerable.
Turtles are long-lived creatures, with some individuals exceeding 100 years. However, this characteristic can also work against a species, since long-lived animals generally do not mature until later in life. A late-maturing animal must survive all the perils and threats for several years before contributing its genes to future generations. In this case, loss of near-mature individuals is a significant threat to the future of the species. Unfortunately, near adults are often the very individuals in greatest demand for harvest.
On reaching maturity, a turtle will often travel considerable distances over land in search of nesting sites. This poses yet another danger in the world of the 21st century – collision with cars. Turtles crossing roads are among the wildlife victims of our fast-paced society, often in very significant numbers.
So, all in all, the turtle’s life is hardly an easy one – a fact which makes turtles a very special part of our Texas natural history.
What’s in the Future for Turtles?
Between the desire for homes, roads and hotels along waterways where turtles come to lay their eggs; the desire to keep these beautiful creatures as pets; and the appetite of some for turtle meat, pressures on turtles are constant. Adding the impact of fishing without effective turtle exclusion devices, and these threats increase. Effective management and education can help these animals to survive.
What Can I Do?
By far the greatest threat to turtles comes from habitat destruction. How many people, when looking out over a swamp, will see a valuable natural resource critical to wildlife? How many see a muddy stream and think of wildlife habitat? Dredging, channeling and altering the course of rivers can permanently remove needed habitat for turtles. Draining swamps, converting land for agricultural uses, water pollution, and other human activities in and around water can permanently displace turtle populations. Building along stream banks often paves over or alters critical nesting sites.
Needless shooting of turtles that are simply left to rot is a waste of this valuable resource. Turtles are often wrongfully blamed for depleting fish populations. Taking the life of a non-game animal for target practice or from misguided zeal to protect fishing grounds does not demonstrate good outdoor ethics.
Taking an animal home as a “souvenir” of your visit to turtle habitat often results in a “pet” that meets a slow demise through neglect or ignorance. While often promoted as good pets, turtles, like any other animal, require attention and care. While it is legal to keep turtles as pets in Texas, check the regulations to ensure that you remain within the legal framework. They can be found at www.tpwd.state.tx.us/business/permits/land/wildlife/media/nongame_regulations_faqs.doc. This page will also give you information on collecting animals commercially, which is regulated in Texas.
Many turtles meet an untimely demise while trying to move across lanes of traffic while moving between waters. Seeing a turtle trying to cross the road is an increasingly common occurrence, especially during nesting seasons. Helping the turtle cross the road is the humane thing to do and might even save the animal’s life. Relocating it to a supposed “better home” can be detrimental to the animal’s future. Turtles, like other animals, have established home ranges and are likely to leave the “paradise” you found and try to return home. This is likely a death sentence for the turtle. Traveling until exhausted while looking for familiar grounds, and trying to avoid additional threats, they are likely to cross several roads and get crushed.
Sea turtles whose diet includes jelly fish are increasingly harmed by floating plastics. Sadly, turtles and other aquatic life are found dead of starvation with plastic clogging their stomachs. Coastal TPWD staff repeatedly find floating plastic bottles with diamond-shaped cuts out of it -- turtle bites!
Creating Habitat for Turtles
Gardening for wildlife is becoming a growing hobby in Texas, with many of your neighbors and friends considering the needs of birds, butterflies, squirrels, and even toads in their landscaping decisions. Why not consider a turtle habitat as a portion of your backyard habitat? When you install your pond, consider using mud or sand as a substrate for at least part of the area. Install plants that will be used by the turtle both as shelter and as food resources. Be careful to add a gently sloping entrance/exit from the pond. Sand and soft soil to a depth of several inches should be available near the pond for egg laying. Rocks, logs and other basking surfaces, with easy access to the water, should be available. Resist the temptation to go out and “adopt” a turtle to move to your habitat. If the conditions are right, the turtles will find and use the habitat you’ve created. Become a member of a local herpetological society, where you can learn more about turtles and tortoises; often these societies help place unwanted turtles and other reptiles in new homes with informed people.
- Texas Turtles (TPWD booklet)
- Adventures of Tortuga Tex (TPWD comic strip format)
- Fact sheets on some of the turtles found in Texas:
- Eastern Box Turtle (Terrapene carolina)
- Green Sea Turtle (Chelonia mydas)
- Hawksbill Sea Turtle (Eretmochelys imbricata)
- Kemp's Ridley Sea Turtle (Lepidochelys kempii)
- Loggerhead Sea Turtle (Caretta caretta)
- Ornate Box Turtle (Terrapene ornata)
- Red-eared Slider (Trachemys scripta elegans)
- Texas Diamondback Terrapin (Malaclemys terrapin littoralis)
- Texas Tortoise (Gopherus berlandieri)
- Yellow Mud Turtle (Kinosternon flavescens flavescens)
- From the TPW Magazine
- Entranced by Sea Turtles A conservation camp in Mexico gave new meaning to the word “vacation.”
- Natural History Guide: Dixon, James R. 2000. Amphibians and Reptiles of Texas. Texas A&M University Press. College Station.
- Biology, conservation, ecology and natural history of Texas turtles - www.texasturtles.org
- University of Texas range and diagnostic features of Texas turtles - www.zo.utexas.edu/research/txherps/turtles/