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The Eastern Mud Turtle (Kinosternon subrubrum) is a small semi-aquatic, generally freshwater turtle. Turtles are members of the phylum Chordata and the class Reptilia. The eastern mud turtle lives in the southeastern parts of the United States. This species of turtles generally live both on land, underground during the cold months, and reside in water for the remainder of the year. These turtle generally mate underwater, but lay their eggs on land. They can be defensive, which often leads to fighting. The main cause for death of these turtles is from habitat destruction or getting crushed by cars when crossing a highway.
The eastern mud turtle is generally easy to tell apart from other species of turtles mainly because of its small size. A mud turtle has the ability to close its entire body into the shell due to a double-hinged plastron  that has 11 scutes  The eastern mud turtle can often be confused with some species of musk turtles, but the main way to the tell the difference is that the 9th marginal scute is not enlarged and that the plastron of a musk turtle has a single hinge. The carapace on a mud turtle is smooth, oval-shaped and does not contain a keel. When trying to identify a male mud turtle from a female mud turtle the main difference is that the males generally have a smaller body but a longer tail. The male's longer tail helps him to mount a female during the mating ritual!
Mud turtles are known for their dull shell colors and relation to the smelly musk turtles. African and American mud turtles are very different and are not closely related. Their only similarities are in their choice of habitat, both preferring shallow, slow moving bodies of water with muddy bottoms, and having a dome shaped carapace. They can grow up to about 5-inches, and can live up to 50 years of age.
The length of a hatchling's carapace generally ranges from .6 inches to 1 inch when first born. The hatchlings are generally black on top and red, yellow, or orange mixed with black on the plastron underneath. The hatchlings generally have a larger head and a more round, deep and differently patterned shell. On average, an adult eastern mud turtle grows to be about 3-5 inches long. An adult eastern mud turtle has a light brown or olive to black colored carapace and light brown to yellow or orange colored plastron. The skin of the turtle is usually light brown to olive. The head can sometimes be darker than the rest of the turtle’s body and generally has broken yellow markings on each side.
The taxonomic classification of the eastern mud turtle begins with the kingdom Animalia. The phylum is that of Chordata, which includes vertebrates. The class is Reptilia, which includes the orders Crocodilia, Sphenodontia, Squamata, and Testudine. The order Crocodilia includes animals such as alligators and crocodiles, Sphenodontia includes tuataras, Squamata includes snakes and lizards, and Testudine includes tortoises and turtles. The family of the eastern mud turtle is Kinosternindae, which includes the musk and mud turtles. The genus is Kinosternon, which includes all of the different species of mud turtles. Which leads to the scientific name of K. subrubrum.
Fossils of K. subrubrum have been found dating back to around 5.3-2.5 million years ago, during the Pliocene epoch. Some of these fossils have been found in Kansas, Florida, Georgia, and South Carolina.
Kinosternon subrubrum is a semi-aquatic species of turtles that can be found in or around wetland habitats. They generally are found in freshwater environments, but sometimes they are found in slightly brackish waters as well. These turtles are usually found in shallow waters such as ponds, bogs, marshes, roadside ditches, or wet area where they can retreat underwater. The turtles submerge themselves half in the water and half exposed during the time that they spend in the water. This turtle can dive to around three meters and can hold its breath for 20 minutes without coming back up to the surface. The turtles spend the majority of their year active if the temperature is above 20°C. The reason why these turtles are most active above these temperatures is because the higher the body temperature, the higher the metabolic rate of the turtle. When the turtles are not found on land or in the water, they are in hibernation in burrows made by themselves or other larger animals. This turtle is quite active on land as well as in the water. It is usually found on land after wet weather and during the spring, summer, and fall seasons.
The eastern mud turtles are generally found in the southeast region of the United States. They can be found as far north as Long Island or as far south as Florida. They can also be found as far west as eastern Texas all the way to the eastern shores of the United States.
The eastern mud turtle is an omnivore, which means that it eats both plants and animals as a source of nutrition. This turtle is said to eat earthworms, snails, crayfish, small crabs, spiders, beetles, larvae of different insects, caterpillars, frog eggs, tadpoles, small frogs, small salamanders, dead fish, algae, and different types of aquatic plants and grains. This turtle has a strong enough bite to crack open small shells like that of the snail and crab. It primarily feeds underwater scavenging into the mud and sand on the floor for some of the aquatic organisms and plants. These turtles are rarely seen feeding on land, but because they spend a short period of the year on land it is predicted that they also feed out of water the majority of the time.1
The eastern mud turtles do have a significant amount of predators as well. They are often preyed upon when they are still in the eggs or hatchlings. Usually opossums, weasels, skunks, raccoons, foxes, crows, snakes, shrews, and other carnivores will consume the eggs in the nest of a mud turtle. The small size of the hatchlings and younger turtles makes them an easy prey target for predators such as snakes and aquatic birds. Because of the small size of the turtle, it does not have many defense mechanisms. Its primary defense is to retreat back into the shell and use the double-hinge plastron to close up as tightly as possible. It also tries to bite when it feels threatened, but the bite is usually not enough force to fend off from larger predators.
In areas where K. subrubrum live there can be ample numbers of individuals. The population size of these turtles can reach numbers of around 200 individuals per hectare over the course of a year. Biomasses of mud turtles can be high as well, reaching around 30 kilograms per hectare. In areas of South Carolina the female to male ratio was one to one and had a survival rate of about the same for both male and female.
K. subrubrum is generally active for the majority of the year during the warmer seasons. Some mud turtles remain on land from spring or summer until the beginning of spring comes around again. These turtles are active both during the day and the night. During the day they usually sunbathe in the shallow water on logs, brush, or close to the shore in the mud. The turtle is most active on land in the early morning or late night after rain. When the turtle is ready to burrow itself for hibernation it digs a hole barely under the water and backs down into it. If the turtle is going to hibernate on land it usually finds a burrow already dug for it to spend its winter months in. When the wet habitat that the turtle is living in dries, it usually digs into the bottom to try and find a more moist area or it just leaves and migrates on land. If this happens the turtle will migrate as far as 300 meters from its habitat. Turtles can swim at speeds up to 12.8 cm/sec when travelling. Eastern mud turtles get defensive and occasionally fight each other, which usually results in one retreating. Turtles are generally not very active animals when it comes to pronounced behavioral traits.
K. subrubrum sexually mature at different ages across separate populations in different states or areas. In Oklahoma region males mature at around four years of age and females around five years. In Florida both males and females sexually mature at around three or four years old. The mating season for the eastern mud turtle is around the middle of March until the end of May. In order to attract a mate, females secrete a scent from a special gland. This scent can also double as a defense mechanism for these turtles. When these turtles mate, it is usually done underwater. Female mud turtles contain an area within their reproductive system that stores sperm so that it can fertilize all of the eggs that have been laid. Once the eggs are fertilized the nesting period begins. Mud turtles nesting sites are not located in the water, but fairly close. The nests are usually composed of debris and soil with the opening of the nest not hidden very well. When the location of the nesting ground suits the female she digs a hole until she is almost completely submerged underneath the ground. Then she turns around and lays the eggs. The eggs that the females lay can be easily broken and are fragile. After she lays the eggs she leaves the nest and may return to the water. A female generally lays three to four eggs at a time. The eggs usually hatch around August or September when it is warm enough to develop properly.
Kinosternon subrubrum has a conservation status of least concern. These turtles are not vulnerable in the wild yet. Their primary cause of death is from being run over by cars when attempting to cross over a busy highway to change habitats. Another major cause of death for these turtles is habitat destruction. Tearing down natural habitats to build new buildings and subdivisions is causing entire communities of mud turtles to be completely destroyed. Humans have also destroyed some communities of this species by spraying pesticides. In order to maintain the conservation status of least concern, efforts need to be made to decrease the mortality rate of highway deaths and habitat destruction.
Mud turtles are omnivorous and sometimes carnivores and will consume almost anything they can catch including fish, worms, insects, grubs, crustaceans, tadpoles, small berries, plants and even carrion.
Mud turtles prefer shallow, slow-moving bodies of water with a sandy or muddy bottoms where they can search for food. They spend a significant portion of time out of the water basking in the sun and foraging for food. They prefer warm, sandy or muddy areas such as wetlands and bayous.