The yellow mud turtle is a small, uniformly colored turtle of the Great Plains. The chin and throat are normally yellow. The upper shell is somewhat flattened and usually olive brown; note that populations in northeastern Missouri typically have darker shells than those occurring in other parts of the state. The scutes (scales) on the carapace (upper shell) are outlined in dark brown. The plastron (lower shell) is yellow brown; its scutes normally have dark brown margins, too. The limbs and upper parts of the head and neck are olive. The tail of the yellow mud turtle ends in a clawlike, horny tip. Adult males can be distinguished from females by concave plastrons and long, thick tails. As with other members of the musk and mud turtle family, this species gives off an offensive, musky odor when captured.
Similar species: A key character for distinguishing the yellow mud turtle from other members of its family is the height of the ninth marginal scale on the carapace. This scale is much higher toward the middle of the upper shell than the eighth marginal scale.
The closest relative in Missouri is the Mississippi mud turtle (K. subrubrum hippocrepis), which is found only in the Bootheel and some counties along the Arkansas border in southeastern Missouri. Thus our two mud turtles occur in very different parts of the state.
Compared to the eastern musk turtle (in genus Sternotherus), mud turtles (genus Kinosternon) have larger plastrons (lower shells), and the front and hind parts are both movable.
Adult upper shell length: 4 to 5 inches; occasionally to 6½ inches.
In Missouri, the yellow mud turtle is restricted to a few southwestern counties, some locations in west-central Missouri (the Kansas City area), and a few marshes in far northeastern Missouri. Missouri’s mud turtles are quite separated geographically.
Habitat and Conservation
In Missouri, the yellow mud turtle lives primarily in areas with open, sandy ridges close to wetlands. Individuals will begin to emerge from overwintering sites in early to mid April to move into nearby wetlands. A variety of aquatic habitats, especially those with muddy or sandy bottoms, may be used: marshes, rivers, sloughs, oxbow lakes, ponds, temporary pools, flooded fields, and water-filled ditches. Overland movement is common during the active months, with most terrestrial activity taking place in early morning, evening, and at night.
From late April through early July, most individuals are in wetlands for courtship, basking, and feeding. During the hot, dry summer months of July and August, individuals are buried in the sandy substrate at a depth of about 10 inches. Some turtles might emerge after this inactive summer period to move into wetlands for about a month (September into October) before settling in a location for the winter. Most individuals overwinter from October through March buried in the sandy soil, usually about 18 inches below the surface.
Yellow mud turtles eat a variety of aquatic animals, including aquatic and terrestrial insects, snails, crayfish, tadpoles, and dead fish. They occasionally eat aquatic plants. A study in northeastern Missouri revealed that snails were a favorite food. Researchers have also noticed that captive yellow mud turtles ate nightcrawler earthworms while they were buried in an aquarium filled with moist sand.
The yellow mud turtle is listed as endangered in the state of Missouri because of its restricted range, limited habitat, and well-documented decline. It is in danger of being extirpated from our state. Predation of eggs, as well as adults, by raccoons and other mammal predators is a continued threat to this species. Although considerable efforts are under way to ensure that this species remains a part of Missouri's biodiversity, populations continue to decline, and this species' long-term future in Missouri is uncertain.
At one time, two subspecies of yellow mud turtle, Kinosternon flavescens, were recognized, and both occurred in Missouri. The yellow mud turtle (K. f. flavescens) occurred in southwestern Missouri and in the Kansas City area, while the Illinois mud turtle (K. f. spooneri) was found in extreme northeastern Missouri. Scientists, however, determined that the Illinois mud turtle wasn't different enough to be considered a valid subspecies, so at this point, only the yellow mud turtle is recognized in our state. Additional genetic studies are likely needed.
This species is active April–October. Courtship and mating occur between late April and mid-May. In June or July, the female digs a nest hole in a usually sunny spot with well-drained sand or soil, and lays 6–8 eggs. She may not lay all her eggs at once but instead wait a day or two and make another nest in the same general area. This can keep a lucky nest predator from finding all her eggs. Some females may remain in the nest with the eggs, especially in dry years. Hatching occurs from late August to mid-September. Young turtles remain in the nest until the next spring. In northeastern Missouri, they emerge in May. Individuals attain sexual maturity at age six or older. Females have been documented living in the wild for at least 50 years and likely beyond 60.
The wetlands inhabited by these turtles are also home to many species of fish and waterfowl that are pursued by anglers and hunters. Protecting the habitat for these turtles helps fishers and duck hunters, too.
Turtles are important to humans symbolically. They represent patience, longevity, wisdom, and perseverance. They figure into hundreds of ancient myths worldwide. Each species has a unique character that humans can appreciate. Native Americans used turtle shells to make rattles.
As predators, they help keep populations of insects, snails, crayfish, and amphibians in balance. As scavengers of dead fish, they help to clean the water. As prey (for they are vulnerable as eggs and young), they feed animals ranging from insects to birds, snakes, and mammals.
The American mud and musk turtle family (Kinosternidae) occurs only in North and South America and is made up of rather small, dull-colored turtles. Species within this family occur from Canada to Argentina and have been classified into 25 species in five genera. Three species, representing two of the genera, occur in Missouri: the yellow mud turtle (Kinosternon flavescens), Mississippi mud turtle (K. subrubrum hippocrepis), and eastern musk turtle (nicknamed the “stinkpot,” Sternotherus odoratus). All members of this family possess small scent glands along the seam between the upper shell and lower shell. When captured or roughly handled, musk and mud turtles produce a strong, unpleasant smell.