Mud turtles, belonging to the genus Kinosternon, are small, semi-aquatic reptiles found across North and South America. They prefer shallow, often muddy, aquatic environments. These turtles spend much of their time on the bottom of water bodies rather than basking extensively, thriving in varied freshwater habitats from clear brooks to temporary ponds.
Defining Physical Attributes
Mud turtles typically measure around 15 cm (6 inches) or less in carapace length. Their upper shell, or carapace, is oval-shaped, smooth, and lacks a prominent keel or ridge in adults. The carapace coloration varies from olive to dark brown or almost black, often without distinct patterns. A distinguishing feature is their plastron, or lower shell, which is large and double-hinged, allowing them to partially close their shell for protection by pulling in their head, limbs, and tail.
The plastron’s color ranges from yellowish to brown and may display a dark pattern. Mud turtles have 11 marginal scutes, the plates around the edge of the shell, rather than the more common 12. Their head is medium-sized and may have irregular streaks, spots, or mottling in lighter colors, sometimes with two light stripes on each side of the face. Their skin is grayish, and their feet are webbed. Males have a longer tail with a blunt spine at the tip and rough, scaly patches on the inside of their hind legs.
Ecological Role and Habitat
Mud turtles inhabit a broad geographic range, from New England in North America down to northern Argentina in South America. In the United States, they are found across the southeastern and northeastern regions, extending west into central Texas and north up the Mississippi Valley. These semi-aquatic turtles divide their time between water and land. They prefer shallow, slow-moving freshwater environments with soft, often muddy, bottoms and abundant vegetation, including ponds, lakes, swamps, marshes, ditches, and even brackish water near salt marshes or on coastal islands.
Mud turtles are poor swimmers, preferring to walk along the bottom of water bodies, and rarely bask extensively. They are omnivorous, consuming a varied diet primarily of animal matter such as insects, crustaceans, mollusks, worms, small fish, and fish eggs. They also consume aquatic vegetation and carrion. During drought or winter, mud turtles burrow into mud or soil and enter a state of dormancy, known as aestivation in summer or hibernation in winter.
Distinguishing from Similar Turtles
Mud turtles are often confused with musk turtles (Sternotherus genus) due to their similar size and semi-aquatic nature. Both are small, under 15 cm, and can secrete a foul-smelling musk when threatened. A primary difference lies in their plastron, or lower shell. Mud turtles have a large plastron with two distinct hinges, allowing for some closure. Musk turtles have a smaller plastron with either one less obvious hinge or no hinge at all, providing less protection.
The shape of their shells also differs. Mud turtles have a smoother, less keeled carapace compared to musk turtles, which often have a more prominent ridge along their spine. Musk turtles have fleshy barbels along their chin and neck, a feature absent in mud turtles. While mud turtles are semi-terrestrial and spend time on land, musk turtles are almost entirely aquatic, venturing onto land mainly for nesting.