Spiny Softshell Apalone spinifera - Special Concern

Family: Trionychidae

General Description: Spiny Softshells are named for the characteristically smooth, round, flat carapace. Unlike most other turtles, the bony elements of the carapace and plastron are reduced. The limbs are highly webbed and form a paddle to assist it while swimming in swift currents. Adult males reach sexual maturity at a carapace length of 3–4 inches (7.6–10.2 cm) and females reach sexual maturity at a carapace length of 11 inches (27.9 cm). The body color and carapace is brown to olive-green in coloration, however patterning on this carapace varies by sex: males have a series of dark, circular spots covering the carapace and females have a more blotched pattern. Juvenile females will possess dark, circular spots similar to males, but these fade as they age. The head and neck are often mottled with light and dark specks. The plastron is pale and unmarked. On the head, a dark-bordered whitish or yellow line is present from behind the eye that runs to the neck as well as a similar line along the upper lip. Unlike Smooth Softshells (Apalone mutica), the Spiny Softshell has fleshy tubercles on the anterior margin of the carapace and has a projection extending into the nostril from the nasal septum. In addition to being smaller than females, males have a proportionally larger, longer tail, with the cloaca being located at the tip of the tail.

Behavior: Spiny Softshells feeding primarily on aquatic insects and fish, but will also eat snails, mollusks, amphibians, and carrion. Turtles overwinter among the substrate of the habitats where they are found.

Reproduction: Individuals breed in the early spring, with eggs being laid early June. Nests are made on bare sandy substrates, such as on sandbars, with little to no vegetation present. Eggs are white, leathery, and ovoid in shape. On average, females will lay 12–18 eggs that will hatch in August. Sex of hatching turtles is determined genetically, rather than by temperature. Males reach sexual maturity in 4 years while females take up to 7 years.

Habitat: Spiny Softshells are highly aquatic turtles and are considered habitat generalists. They can be found in almost any suitable aquatic habitat, including rivers, lakes, reservoirs, and wetlands.

Species Range: This species has an extensive range thought much of the central and eastern United States. This species can be found from the Great Lakes Region south to the Gulf of Mexico, west to the Rocky Mountains and Texas, with scattered populations in New Mexico, Arizona, and California.

South Dakota Range: This species occurs in the lower reaches of the Missouri River and other large rivers, including the Belle Fourche, Big Sioux, Cheyenne, James, Keya Paha, Vermillion, Whetstone, and White rivers.

South Dakota Status: The Smooth Softshell is listed on the South Dakota Natural Heritage Program. Any sightings of this species should be reported to South Dakota Game, Fish and Parks (report observation).

Account written by Drew R. Davis

Distribution Map
Distribution map of Spiny Softshell (Apalone spinifera)

County level distribution of this species in South Dakota. Map generated from data collected from voucher specimens and photographic records. See About for additional information.

Photographs
Spiny Softshell (Apalone spinifera)
Spiny Softshell (Apalone spinifera)
Spiny Softshell (Apalone spinifera)
Spiny Softshell (Apalone spinifera)