The Sonoran Mud Turtle is a medium sized (up to 6¼ inches long) turtle, somewhat elongated, with an olive-brown shell and grey mottled skin. The shell is often partially covered with algae. The turtle has several fleshy projections (called barbels) located under the chin. Males have tails with a hooked tip.

The Sonoran mud turtle is usually found near springs, ponds, intermittent streams or creeks in oak to pinyon-juniper woodlands or pine-fir forests. Occasionally it may be found in desert and grassland regions as well as in stock ponds. They are active year round although they may not feed in colder months. The species is distributed from central Arizona to Durango, Mexico and southeastern California (perhaps, some reports indicate the turtle may now be extinct in California) to west Texas. The turtle feeds mainly on insects, crustaceans, snails, fish, frogs, tadpoles, though will eat plant matter in a pinch. Nesting occurs between May - September and females lay a clutch of from 1 to 11 eggs.

Size
3 1/8 - 6 1/2 inches in shell length (7.9 - 16.5 cm) (Stebbins 2003)

Appearance
A dark, medium-sized turtle with a smooth and elongated carapace, and mottled markings on the head, neck and limbs. Light markings on the head tend to form a pair of stripes on each side of the head. The feet are webbed, the tail is short, and there are barbels on the throat.

Carapace color is olive to dark brown, with darkly-marked seams. 1 or 3 lengthwise keels may be present. The plastron is hinged and yellow to brown in color with darkly-marked seams.

Males are smaller with a concave plastron and a longer thicker tail.

Behavior and Natural History
Most information for this species comes from individuals studied in Arizona. Little is known about the life history of California animals.

Active during the day and at night, becoming more nocturnal in hot summer weather. Active all year, though feeding may not occur during the cold of winter. Higher-elevation populations may be forced to hibernate in winter.

Mostly sedentary, rarely moving out of or away from water, but occasionally migrates considerable distances from one waterway to another.

Diet
Omnivorous, eating mostly animals including snails, fish, frogs, tadpoles, crustaceans, and other small invertebrates, along with some plant material.

Reproduction
Females lay a clutch of 1 - 11 eggs from May to September, which take almost a year to hatch. Sometimes as many as four clutches a year are laid. Females reach sexual maturity 6 years, males in 2- 6 years.

Range
Historical range was southwestern New Mexico, southern Arizona, southeast California along the Colorado River, and Chihuahua and Sonora, Mexico. Now apparently extinct along the Colorado River.

In California, the historical range was along the Colorado River from the Nevada Border south to the Mexican border.

Sonoran Mud Turtles also began dispersing into agricultural canals in the Imperial Valley before they disappeared from California. Some of the old California records include Palo Verde, Yuma Indian Reservation, Ft. Mojave, and near Laguna Dam.

Habitat
In California, formerly found in the desert in overflow channels of the lower Colorado River. Normally occurs in ponds and slow-moving tree-lined watercourses, including quiet pools in streams, oxbows, ponds, creeks, and cattle tanks. Usually found in woodlands, but occasionally in grasslands. Needs a permanent or nearly permanent water source.

Taxonomic Notes
Two subspecies have been described, including Kinosternon sonoriense longifemorale, the Sonoyta Mud Turtle.

Conservation Issues (Conservation Status)
Endangered.

This species appears to be declining over much of its range. The last known verifiable record along the Colorado River was from near Laguna Dam in 1962.

The reasons for this turtles apparent extinction in California are uncertain, but most likely a combination of introduced aquatic predators such as bullfrogs and Louisiana red swamp crayfish, introduced vegetation, especially salt cedar, and widespread water and land alterations along the Colorado River including reservoirs, dams, and agriculture, is responsible.