Pseudemys texana

Geographic Range

Texas river cooters ( Pseudemys texana ) are native to the Nearctic region, strictly in central and south-central Texas. Their range is limited to the Brazos, Colorado, Concho, Llano, San Saba, Guadalupe, Neuces, and San Antonio watersheds.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Texas river cooters are aquatic animals. They are normally found in the shallow water of freshwater rivers, but they can enter riverine pools as deep as 4m. River cooters have also been observed in lakes with sewage sludge. They can also inhibit riverine impoundments, nearby cattle tanks, canals, and irrigation ditches. River cooters are most commonly found in clear water with soft, dense vegetation beds or in wetlands near their permanent water source.

Before laying eggs, female cooters move onto land and dig a nest. Most cooters nest in mixed short-grass areas. Nests on bare soil and mulch have also been observed. Most nests had no cover while the remaining nests were located near trees, landscaping, and manmade structures. Washington (2008) observed the distance from the water to nesting sites and the average temperatures of soil and air during nesting. She reported that these turtles dug nests 14.63 to 153.63m from water. Recorded air and water temperatures were 23.9°C to 35.2°C and 21.9°C to 28.3°C, respectively.

On moderately hot days, Texas river cooters use fallen trees and broken branches on the shoreline for basking in the sun. Hill (2008) reported that temperature range for basking was between 25.3 to 46.8 °C. In cooler weather, Texas river cooters use the shoreline to hibernate.

• Habitat Regions
• freshwater freshwater

• Aquatic Biomes
• rivers and streams

• Wetlands
• marsh marsh

• Other Habitat Features
• riparian riparian

Physical Description

Texas river cooters possess narrow yellow head striping with spots and dashes. Their skin is black with yellow and white striping. A singular stripe curves around their jaw with a yellow spot behind the eye. Their brown carapace is flat in the middle and scored around the edge with fine yellow webbing and swirls for coloring. Their plastron has little, if any, pattern in older river cooters, but the rim may have a red tint. River cooters can become melanistic as they age. Male river cooters have a thicker tail and their vent is behind the carapacial rim. The carapacial rim is part of the carapace that covers the plastron. Female river cooters have shorter tails and their vent is anterior to the carapacial margin. Male river cooters have longer and more noticeable foreclaws than female cooters.

Adult male river cooters are shorter and flatter than female cooters. Lindeman (2007) reported the body size of adult male and female river cooters across their range. Male cooters had an average carapace length (CL) of 142.4mm (range of 89-191mm CL). Despite this large range, males’ carapace lengths rarely exceeded 170mm. Mature males' average plastron length (PL) was 122.9mm (range 78 to 161mm PL). Linden (2007) reported that female river cooters' average carapace length was 245.9mm (range 223-274mm CL), while their average plastron length was 223.1mm (range 213-241mm PL).

The carapace on juveniles is the same brown color as adults. The pattern is lighter than adults with five or six obvious lighter yellow rings and swirls. The pattern will diffuse and texturize with age. The plastron is yellow with thin black lines on the edges. Lindeman (2007) measured unsexed hatchlings and reported an average carapace length of 48.0mm (range of 41-53mm CL). At one year old, these same turtles recorded an average carapace length of 69.0mm (range 60-78mm CL). At two years old, these turtles had an average carapace length of 74.0mm (range 60-84mm CL). The plastron of unsexed hatchlings averaged 45.0mm (range 41-53mm PL). After a year, the same turtles had an average plastron length of 61.2mm (range 54-66mm PL). At two years of age, they had an average plastron length of 66.0mm (range 55-75mm PL).

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

Development

Texas river cooters rely on temperatures in the nest for sex determination. Males are produced in colder nest temperatures while females are produced in warmer nests. Nests with a temperature between 21.5°C and 27°C predominately produce males. Temperatures between 27.5°C and 29.5°C produce mixed sex ratios. Only females are produced in nest temperatures at or above 29.6°C. Texas river cooters’ incubation time is between 80 and 150 days. This time varies based on the temperature, covering, and the amount of water. Large amounts of water in the nest are found the increase the incubation time. Nests with a smaller temperature tend to have more covering and an increased incubation time.

They grow indeterminately, meaning they continue to grow throughout their lives. Male hatchlings have an estimated plastron length of 34mm while female hatchlings have an estimated plastron length of 24mm. Male river cooters are mature at 3 years old or when their plastron length is larger than 78mm. Females are considered mature after 6 or more years and when their plastron length is larger than 233mm. Female river cooters have a growth rate of 0.129mm per year while males' growth rate is 0.191mm per year.

• Development - Life Cycle
• temperature sex determination
• indeterminate growth indeterminate growth

Reproduction

Female Texas river cooters use pheromones to attract potential mates. Mating begins in early spring in March and April. The males will sniff the females’ cloaca when looking for a mate. Males will shake their foreclaws and extend their forearms to attract female cooters. Texas river cooters are polygynandrous, meaning males and females have multiple partners in their lifetime.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Texas river cooters begin mating in early spring, in March and April. They nest from May until June. Gestation period for river cooters is estimated from 60 to 70 days. Female cooters lay between 0-3 (typically 1) clutches of 4-19 eggs during this period. Larger females lay larger clutches. Females have only been observed nesting diurnally. The process of leaving the water, ovipositing, and returning to the water takes the females 2.5-3 hours. August and September are when hatchlings will emerge. The eggs incubation period ranges from 80-150 days; this range can be affected by the amount of water and nest temperature. Birth mass is not reported but lengths at hatching are estimated: average plastron lengths of 34mm for males, and 24mm for females. These turtles are immediately independent at hatching. Male cooters are sexually mature at 3 years old, while females can take 6 or more years to mature.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Female river cooters have very little parental investment after nesting. They make the choice to place the nest near the water’s edge or farther away. Male rivers cooters are only present for mating.

• Parental Investment
• no parental involvement
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

The maximum lifespan of Texas river cooters is unknown. Texas river cooters probably have similar longevity to river cooters ( Pseudemys cocinna ), which is 44 years. Texas river cooters can also be kept in captivity, but lifespans have not been reported.

Mortality rate for eggs is high in wild populations. Washington (2008) found 59.2% predation on nests was by raccoons ( Procyon lotor ). Only 45.65% of protected nests produced hatchlings.

Behavior

Texas river cooters are diurnal. These turtles usually bask alone, but site size and orientation can contribute to basking in groups. Hill (2008) observed the effects of urbanization on basking. Many turtles chose areas with high shoreline modification. These modified shorelines had less woody vegetation. They also chose to avoid areas with high daily human disturbance.

During the mating season, the males will shake their claws and extend their forearms to attract mates. The female river cooters emit pheromones the male can smell from her cloaca. If the male senses these pheromones, he will mount the female. Before laying eggs, female cooters move onto land and dig a nest.

Between seasons female river cooters migrate longer distances than males. Franklin (2006) reported that females migrated about 289.42m from their fixed locations while males migrated 163.14m. Texas river cooters are a diurnal species. They do not hibernate, but their metabolic rate is relatively slow during colder weather.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• migratory migratory
• social social

Home Range

Texas river cooters' home range is about 650m including land on which they bask. Females' ranges are larger (3.77ha) than males (2.06ha), but their ranges overlap. Between seasons female river cooters migrated greater distances than males; females migrated about 289.42m from their fixed locations while males migrated 163.14m. Texas river cooters are not territorial.

Communication and Perception

All reptiles have pheromones. Aquatic turtles have two primary spots where these will emit: the chin glands and the cloaca. When looking for mates, males will chase and sniff the females’ cloaca. River cooters receptor cells likely function similar to the pond slider ( Pseudemys scripta ). Their receptor cells contained high levels of galactosamine sugar residues. These residues functions as the pheromone signal.

The courtship in turtles involves titillation. Titillation is when the males extend their forearms and vibrate their foreclaws in front of the female. The female will choose if he is suitable to mate. They also use tactile efforts to forage, dig nests, and bask. Turtles perceive the world in color. They have a pigmented oil that allows for color vision.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Adult Texas river cooters of both sexes are primarily herbivorous when mature. The main plants in their diet are hydrilla ( Hydrilla verticillata ), Carolina fanwort ( Cabomba caroliniana ), parrot feather ( Myriophyllum ), common coontail ( Ceratophyllum demersum ), delta arrowhead ( Sagitaria platphylla ), cone-spur bladderwort ( Utricularia gibba ) and filamentous green algae (Chlorophyta). Fields et al. (2003) reported stomach contents of river cooters. They found parrot feather ( Myriophyllum ) was present in 90.9% of stomach samples, Hydrilla verticillata in 87.9%, Cabomba caroliniana in 78.8%, and Ceratophyllum demersum in 57.6%. In the stomach contents, 2.1% of their diet was unknown vegetation (2003). Leaves from the plants are the most often consumed.

Juveniles have a more carnivorous diet than adult river cooters. Common prey eaten by juvenile river cooters includes freshwater sponges (family Spongillidae), aquatic insect larvae like mayflies, crayfish (order Decopoda), snails (order Gastropoda) and small freshwater clams ( Sphaerium ).

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore
  • eats other marine invertebrates
• herbivore herbivore
  • folivore folivore
  • algivore

• Animal Foods
• insects
• mollusks
• aquatic crustaceans
• other marine invertebrates

• Plant Foods
• leaves
• algae

Predation

Raccoons ( Procyon lotor ), skunks (family Mephitidae), and red imported fire ants ( Solenopis invicta ) are nest predators. Additional predators at any age include red foxes ( Vulpes vulpes ), striped skunks ( Mephitis mephitis ), laughing gulls ( Larus atricilla ), American crows ( Corvus brachyrhynchos ) and raccoons.

Raccoons are recorded as the most prolific nest predator for Texas river cooters. Fire ants also prey on female river cooters on land and actively digging nests. Irritation from the fire ants may cause the female river cooters to stop nesting and return to the water, keeping them from completing the nesting process. River cooters’ first line of defense is to flee and try to escape from the predators; if they are unsuccessful, they may bite or retreat into their shells. Humans ( Homo sapiens ) are also predators of Texas river cooters. It is not uncommon for turtles to be hit by cars. Male cooters are less like to die from road mortality as they do not travel on land as often as females.

Ecosystem Roles

Texas river cooters are a mainly herbivorous species. Their predators include red foxes ( Vulpes vulpes ), striped skunks ( Mephitis mephitis ), laughing gulls ( Larus atricilla ), American crows ( Corvus brachyrhynchos ) and raccoons ( Procyon lotor ).

Nordemeyer et al. (2020) examined Texas river cooters for parasitic protozoan in red blood cells. They identified 80 apicomplexan ( Haemogregarina ) parasitic infections, primarily in wild cooters. During breeding, these parasites can be transferred to other populations, including captive turtles. River cooters have been observed basking with turtles of other species, which can transfer diseases and parasites. Texas river cooters can also be parasitized by ticks (Ixodidia) and leeches, which can transmit diseases.

Economic Importance for Humans: Positive

Texas river cooters can be kept as pets. They usually cost between $30 and $100 dollars. However, commercial collection of river cooters from Texas waters stopped in 2007. River cooters are also hunted and eaten in the southern United States. There are no restrictions on hunting.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

Texas river cooters can carry Salmonella enterica , which can cause illness in humans. Salmonella can be found in both captive and wild turtles. Salmonella can cause abdominal pain, vomiting, diarrhea, and fever in humans.

• Negative Impacts
• injures humans
  • causes disease in humans causes disease in humans

Conservation Status

Texas river cooters are considered a species of “Least Concern” on the IUCN Red List. They have no special status on the US Federal List, CITES, or the State of Michigan list.

These freshwater turtles face habitat loss, degradation, and invasive species. Red imported fire ants ( Solenopis invicta ) are a direct threat to nesting cooters and their eggs. Fire ants can kill the hatchling or enter the egg through any impurities and kill them. Humans are also a threat to Texas river cooters. They are hunted for food and can also be hit by cars. There is no restriction on hunting.

Although their populations appear stable, the commercial collection of river cooters was stopped in 2007. van Dijk (2011) recommended monitoring at representative locations to allow for more research of their natural history and their conservation needs. Because Texas river cooters tolerate human disturbance, Vermersch (1992) speculated the creation of impoundments and other vegetated waterbodies actually increased their abundance. He also found river cooters were more abundant in 1992 than the 1960’s in the San Antonio River, despite pollution.

Additional Links

Encyclopedia of Life

Contributors

Kendra Earls (author), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.

References

Buhlmann, K., T. Tuberville, J. Gibbons. 2008. Turtles of the Southeast . Athens, Georgia: University of Georgia Press.

Coleman, A. 2008. Effects of Heavy Metals on Freshwater Turtles in a Sludge-amended Lake in South Texas (Master's Thesis) . San Antonio, Texas: University of Texas at San Antonio.

Cornejo-Páramo, P., A. Lira-Noriega, C. Ramírez-Suástegui, F. Méndez-de-la-Cruz, T. Székely, A. Urrutia, D. Cortez. 2020. Sex determination systems in reptiles are related to ambient temperature but not the level of climatic fluctuation. BMC Evolutionary Biology , 20: 103. Accessed November 19, 2021 at https://doi.org/10.1186/s12862-020-01671-y .

Ernst, C., J. Lovich. 2009. Turtles of the United States and Canada, 2nd edition . Baltimore, Maryland: John Hopkins University Press.

Etchberger, C., J. Iverson. 1990. Pseudemys texana Baur Texas cooter. Catalogue of American Amphibians and Reptiles , 485: 1-2.

Fields, J., T. Simpson, R. Manning, F. Rose. 2003. Food habits and selective foraging by the Texas river cooter (Pseudemys texana) in Spring Lake, Hays County, Texas. Journal of Herpetology , 37/4: 726-729.

Flores, J. 2012. Thermal Aspects of Nesting Ecology of the Texas River Cooter (Pseudemys texana) and Red-eared Slider (Trachemys scripta elegans) at Spring Lake, Hays County, Texas (Master's Thesis) . San Marcos, Texas: Texas State University.

Franklin, S. 2006. Home Range of the Texas River Cooters (Pseudemys texana) at Spring Lake, Hays County, Texas (Master's Thesis) . San Marcos, Texas: Texas State University.

Gaertner, J., D. Hahn, F. Rose, M. Forstner. 2008. Detection of salmonellae in different turtle species within a headwater spring ecosystem. Journal of Wildlife Diseases , 44/2: 519-526.

Gans, C., D. Crews. 1992. Hormones, Brain, and Behavior: Biology of the Reptilia . Chicago, Illinois: The University of Chicago Press.

Hill, S. 2008. The Influence of Urbanization on the Basking Behavior of a Central Texas Freshwater Turtle Community (Ph.D. Dissertation) . Waco, Texas: Baylor University.

Knodler, L., J. Elfenbein. 2020. Salmonella enterica. Trends in Microbiology , 28/1: 83.

Kramer, M. 1995. Home range of the Florida red-bellied turtle (Pseudemys nelsoni) in a Florida spring run. Copeia , 1995/4: 883-890.

Lindeman, P. 2007. Diet, growth, body size, and reproductive potential of the Texas river cooter (Pseudemys texana) in the South Llano River, Texas. The Southwestern Naturalist , 52/4: 586-594.

Munscher, E., A. Walde, J. Riedle, S. Ross, N. Salvatico, C. Collins, M. Farris, B. Butterfield, J. Hauge. 2020. Turtle assemblage in a highly altered spring system: Comal Springs, Texas. The Southwestern Naturalist , 64/2: 109-121.

Nordemyer, S., G. Henry, T. Guerra, D. Rodriguez, M. Forstner, D. Hahn. 2020. Identification of blood parasites in individuals from six families of freshwater turtles. Chelonian Conservation and Biology , 19/1: 85-94.

Nordmeyer, S. 2019. Molecular Analysis of Haemogregarinidae in Freshwater Turtles (Master's Thesis) . San Marcos, Texas: Texas State University.

Rose, F., T. Simpson, R. Manning. 1996. Measured and predicted egg volume of Pseudemys texana with comments on turtle egg shape. Journal of Herpetology , 30/3: 433-435.

Rose, F. 2011. Annual frequency of clutches of Pseudemys texana and Trachemys scripta at the headwaters of the San Marcos river in Texas. The Southwestern Naturalist , 56/1: 61-65.

Seidel, M., C. Ernst. 1996. Pseudemys Gray cooters and red-bellied turtles. Catalogue of American Amphibians and Reptiles , 625: 1-7.

Seidel, M., U. Fritz. 1997. Courtship behavior provides additional evidence for a monophyletic Pseudemys, and comments on mesoamerican Trachemys (Testudines:Emydidae). Herpetological Review , 28/2: 70-72.

Strecker, J. 1927. Observations on the food habits of Texas amphibians and reptiles. Copeia , 162: 6-9.

Valenzuela, N., V. Lance. 2004. Temperature-dependent Sex Determination in Vertebrates . Washington, D.C.: Smithsonian Institution.

Vermersch, T. 1992. Lizards and Turtles of South-Central Texas . Austin, TX: Eakin Press.

Washington, A. 2008. Site Selection and Survival of Pseudemys texana and Trachemys scripta elegans Nests at Spring Lake in San Marcos, Texas (Master's Thesis) . San Marcos, Texas: Texas State University.

Whiting, M. 1994. Pseudemys texana (Texas river cooter) nesting interference. Herpetological Review , 25/1: 25.

Womack, L. 2006. Impacts of Red Imported Fire Ants (Solenopsis invicta Buren) on Native Faunal Communities in Two Pine-dominated Forests (Master's Thesis) . Baton Rogue, Louisiana: Louisiana State University.

van Dijk, P. 2011. "Pseudemys texana (errata version published in 2016)" (On-line). The IUCN Red List of Threatened Species 2011: e.T170497A97427865. Accessed September 05, 2021 at https://dx.doi.org/10.2305/IUCN.UK.2011-1.RLTS.T170497A6782942.en .

2016. "Turtles Are Key To Tracing Birds' 'Redness Gene' Back To The Dinosaurs" (On-line). Accessed September 17, 2021 at https://www.forbes.com/sites/grrlscientist/2016/08/03/which-came-first-seeing-red-or-being-red/?sh=5eead68f4415 .