Smooth Softshell Apalone mutica - Special Concern

Family: Trionychidae

Description: Smooth Softshells are named for the characteristically leathery, round, flat carapace. Unlike most other turtles, the bony elements of the carapace and plastron are reduced. Adult females have a carapace length of 7–14 inches (18–36 cm), and adult males have a carapace length of 5–7 inches (12–18 cm). The carapace of adult males is typically tan with dark spots or streaks scattered throughout and a light tan border along the margin. For adult females, the carapace is tan with dark brown mottling. The body color is tan to olive gray. Juveniles have a series of dark spots on the carapace that often fade away as individuals mature. The plastron is white and unmarked. A dark-bordered white line starts behind the eye and runs to the neck. The feet are highly webbed and form a paddle to assist with swimming in swift currents. The feet lack black lines. The neck is long and the head tapers into an elongated snout. Unlike Spiny Softshells, the Smooth Softshell lacks fleshy tubercles on their carapace and does not have a projection extending into each nostril from the nasal septum. In addition to being smaller than females, males have a proportionally larger, longer tail, with the cloaca at the tip of the tail.

Habitat: Smooth Softshells are highly aquatic turtles found primarily in large rivers and streams with moderate to fast currents, though they can also be found in reservoirs and oxbow lakes. Preferred habitats typically have sandy shorelines and sandbars used as nesting habitat.

Natural History: Smooth Softshells feed primarily on aquatic insects and fish but will also consume snails, mollusks, amphibians, vegetation, and carrion. These turtles spend much time basking on sandbars rather than on woody debris or logs. They overwinter in the sandy substrates of the habitats they are found in, with some recorded instances of communal overwintering. Individuals breed in the early spring, with eggs laid in early June. As males attempt courting, unreceptive females will respond by biting the carapace of males. After reproduction, females make nests on bare, sandy substrates with little or no vegetation. Nests can be up to 12 inches (30 cm) deep, and females lay up to 14 eggs, typically in June. Eggs are white, leathery, ovoid in shape, and hatch 8–12 weeks later in August. Sex of hatching turtles is determined genetically, rather than by temperature. Males reach sexual maturity in four years while females take up to seven years

Species Distribution: This species can be found throughout the Mississippi, Missouri, and Ohio river drainages, as well as large tributaries that are within these drainages. The Smooth Softshell reaches as far north as North Dakota in the Missouri River drainage and Minnesota and Wisconsin in the Mississippi River drainage, east to Pennsylvania in the Ohio River drainage, and south to coastal Texas, Louisiana, Mississippi, and Alabama.

South Dakota Distribution: This species primarily occurs in free-flowing segments of the Missouri River and associated large tributaries. Individuals can still be found in reservoirs along the Missouri River, but typically in lower abundance.

South Dakota Status: This species is monitored by the South Dakota Natural Heritage Program. Any observations of this species should be reported to South Dakota Game, Fish and Parks (report observation).

Remarks: Their name refers to the absence of small tubercles on their carapace. Smooth Softshells can survive underwater for extended periods of time due to their ability to absorb oxygen from the water through membranes in the mouth and the cloaca. These turtles are occasionally caught on fishing lines. If this occurs, care should be taken to remove the hook from the individual before it is released.

Distribution Map
Age in years of Most Recent Record
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75+
Phenology of Smooth Softshell (Apalone mutica)
Smooth Softshell (Apalone mutica)
Smooth Softshell (Apalone mutica)
Smooth Softshell (Apalone mutica)
Smooth Softshell (Apalone mutica)
Smooth Softshell (Apalone mutica)