Common turtles of the Rio Grande

Published: October 13, 2009, 12:00 am

Updated: November 18, 2012, 7:35 pm

Topics:

Biodiversity (main) Ecology (main) Rivers (main) Zoology (main) Species (main)

Rio Grande cooter (Pseudemys gorzugi). Source: EOL/Smithsonian

Some of the most common turtles of the Rio Grande are the red eared slider (Trachemys scripta elegans) and the Rio Grande cooter (Pseudemys gorzugi). Chief aspects of these taxa are set forth in the following.

Red eared slider (Trachemys scripta elegans)

Overview of the red eared slider

Canoeing down the Rio Grande on a warm sunny day, hundreds of red eared sliders are sun bathing orbasking inthe rays of the sun in groups and many times in piles on flat rocks or logs. The red eared slider is semi-aquatic turtle that will spend much of its life in warm, fresh, and calm waters eating green vegetation in the flowing river, marshes, or surrounding riparian zones. When the turtles are young and curious many will eat small aquatic species that are floating around. However, as the red eared slider ages many use vegetation as a predominate source of food and will completely avoid eating aquatic animals. These turtles can survive in the wildest deserts such as the Rio Grande to the care of a turtle lover. They are very friendly turtles compared to a typical snapping turtle and serve as great entertainment to watch grow from a quarter size to a full palm.

Native habitat

One can find the Red-eared Sliders in the United States between Illinois and the Gulf of Mexico, to the east coast and west coast of Texas. Many of the turtles will prefer to live in warmer climates thus causing the larger population of the species to be concentrated east and below Colorado to Virginia down to Florida. However, it is important to note that it is very common to find these turtles in similar climates. This may be the result of turtle owners releasing the species in foreign areas, allowing turtles to evolve and adapt to the environment (Frisby, 1).

Physical description

As a newly hatched turtle many will be around an inch in diameter and can grow up to twelve inches once it’s fully grown. Red-sliders can quickly recognized by their red stripes that are located on each side of the eyes. Even as young hatchling the red stripes are easily recognizable. The top of the shell which is referred to as “carapace” is a very smooth texture with black and yellow patterns. The bottom shelf, which is called plastron, is a very smoth like texture with yellow patterns. Although, as newly hatched turtles many have a visibly green and blue like pattern. As the turtle grows the patterns turn more cryptic, making any patterns very difficult to see.

Sexual difference

The most obvious difference between adult male and female turtles is the size. Female turtles will greatly exceed the size of male turtles once fully matured. The size of the tale on male turtles will be bigger than those of females. The placement of the cloaca- a region of a turtle that is used to excrete waste, and reproduce, is in different placement on both female and male turtles. While a female has the cloaca closer to the shell because of its shorter tail the male has is further away from the shell. The male will also have longer claws that are used for courtship or protection from other predator species. Both turtles will have beaks made of keratin that will allow cutting and eating of vegetation or aquatic species.

Size

Stage	Measurement
Hatchling	1 inch (2.5 cm)
Yearling (year old)	2 “-3.5 inches
Sexual Maturity	4 inch (male) 5 inch (female)
Adult	7-9 inch (male) 10-12 inch (female)

• The sizes of turtles do not always indicate the age of the turtle; biologists and aquatic researchers have found that captive turtles grow at a faster rate than those in the natural environment. This is due to over feeding and lack of hibernation for pet turtles. Overfeeding is and issue that many turtles will encounter, if diet is not balanced out. Many studies also show that a significant percentage of captive Red-eared Sliders will live twice as long as wild ones.

Captive turtles versus wild turtles

While many of the captive Red-eared Sliders are being taken care of by owner many do not have to search for food, escape natural predators, or worry about temperature and climate. Many turtles once keep by an owner become dependent thus making them weaker and more susceptible to predators in the wild.

Wild turtles will be more adaptive to harsher climates and will savage for food and hibernate when needed. Many wild turtles will not be friendly to people and will often run or hide from unfamiliar objects. Wild Red-eared sliders will be more susceptible to parasite and diseases.

Rio Grande cooter (Pseudemys gorzugi)

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Overview of the Rio Grande cooter River cooter can be found at a local pet store with other aquatic turtles. However, while they are easy to maintain when young, these turtles can grow too big for an average sized aquarium. (Common turtles of the Rio Grande)

Size and appearance

The river cooter can grow up 12 to 16 inches once fully mature. The size of the turtle will correlate to the amount of food it consumes throughout its life, as well as the natural habitat in which it chooses to live. The carapace (shell) is a flatter surface, with a smoother texture that allows it to swim easily in faster moving waters and away from any prey. The shell of the turtle will range from brown to shades of yellow markings, which will vary greatly with different individual turtles. While male turtles age the shell becomes very dark eliminating any distinct pattern. One distinction between male and female turtles will be the size of the tail and shell. Females will grow distinctively larger than the males with more distinct patterns. The size of the tail on males however will be much longer than those of females.

Habitat

The river cooter will spend much of it life living in freshwater and brackish moving water. The ideal habitat for this species will typically be in lakes, ponds, and marshes concentrated with large amounts of vegetation. Importantly all river cooters have webbed feet which will allow them to be excellent swimmers, allowing them to travel through stronger currents and streams. In large groups they will live on the peninsular floodplains. One important feature within these turtles is the amount of sun that is required. Most turtles will need to sun bath on flack rocks or ledges to maintain a moderate body temperature throughout the year. While asleep these turtles will be submerged in water under deep rooted vegetation, mud, or rocks. These turtles have also adapted to the natural climate. During the winter a turtle can remain dormant for up to two months. During these two months, the turtles will have a relatively low metabolism which allows them to only utilize the oxygen from the water, which they will take in through the cloaca. Turtles that remain dormant through the colder climates will also halt any growth as many do not require any food. While some turtle well remain dormant in the cold others will remain active in areas that stay moderately warm year round.

Reproduction

Similar to other freshwater turtles, the male will be smaller than the female. The male however will have longer claws which are used to attract a mate. Researchers have indicated that turtles will release a pheromone signal while sniffing at a female’s tail, which will cause male turtles to vibrate their nails, and stoke the females face. If the female is receptive, she will sink to the bottom of moving water and allow the male to mount for mating. Mating will commonly take place during the warmer seasons of the year which in most places will be between May through June. The female will search for a secure location on dry land to lay her eggs. The female turtle can lay up to 25 or more eggs in one or more clutches. The eggs will be around 1 to 2 inched and will require around 90 to 100 days of incubation. Hatchlings will be born around august and September of each year.

Distribution

The Rio Grande Cooter can be found throughout the Rio Grande watershed of Texas to northeastern Mexico from Brownsville to the Big Bend north of Del Rio, and the Pecos River drainage of northwestern Texas and southeastern New Mexico.

Resources used in this paper

• Holly Frisby, DVM, MS
• Encyclopedia of LIfe. 2012. Pseudemys gorzugi, Species Curator: C.Michael Hogan
• Veterinary Services Department, Drs. Foster & Smith, Inc.
• C.H. Ernst, R.G.M. Altenburg & R.W. Barbour, Turtles of the World

Citation

McGinley, M. (2012). Common turtles of the Rio Grande. Retrieved from http://editors.eol.org/eoearth/wiki/Common_turtles_of_the_Rio_Grande