Medium-sized (up to 28 cm CL) turtle with tan, brown, or olive carapace with light posterior border. Carapace irregularly patterned with small dark spots or dashes that expand into blotches or mottling in large females. Plastron white to cream. Paired, dark-bordered, white stripes extend across snout to eyes. A similar but expanded pair of stripes extend posteriorly from eyes onto the neck. Feet neither strongly streaked nor patterned. Male smaller than female and has a larger, thicker tail with vent opening beyond rear edge of carapace.
Smooth softshells are found in rivers, large streams, and, rarely, large lakes with sandy or muddy bottoms. These lakes are usually close to a large river. Sandbars are important for basking and egg laying sites. They seem to prefer larger rivers and live in colonies along certain portions
Historic records indicate that the Smooth Softshell once occurred statewide.
County Breakdown: County Name (# occurrences)
Atchison (2), Barber (2), Comanche (1), Cowley (5), Dickinson (1), Doniphan (2), Douglas (29), Ellis (4), Ellsworth (1), Finney (1), Geary (1), Harvey (1), Johnson (1), Kearney (1), Kingman (2), Leavenworth (166), Lyon (1), Marshall (1), Osage (1), Pottawatomie (7), Reno (3), Riley (8), Russell (4), Stafford (1), Sumner (3), Trego (1), Washington (1), Woodson (1)
Female lays multiple clutches of 6 to 26 round, brittle-shelled eggs (ca. 22 mm diameter) in sand banks or bars from late May into July.
Unlike spiny softshells, these turtles are not aggressive and will remain passive even when picked up.
Males and juveniles congregate in sandy shallows to bury in the substrate and bask along exposed banks. Female is more solitary, wanders more, and utilizes deeper water than male. These turtles are active from April and to late September or October. They bury themselves in mud or sand at the bottoms of rivers or lakes to overwinter. They are diurnal and sleep at night underwater buried in sand or mud in the shallows or among submerged trees. They are one of Kansas' most aquatic turtle species. They bask on sand or mud bars or on large logs and rocks, but always at the waters edge. They are wary (more so than even spiny softshells) and will quickly dash into the water at the slightest disturbance.
The diet includes a variety of animal foods but especially aquatic insects
Predators and Defense:
Neonate softshells are eaten by a variety of carnivorous vertebrates including large fish.
Growth and Longevity:
KU 218796, Osage County, John Powell and Beverly Downing, 9 June 1991, carapace length 285 mm (11.25 inches), Collins (1993).
Not known from Kansas.
Most Kansas specimens were collected from the Kansas River below the low water dam at Lawrence, in association with the doctoral research of Dr. Michael Plummer (Plummer, 1975, 1977, 1977). The remainder of the known occurrences are widely scattered across the state. Despite numerous attempts to document this turtle during the study only one specimen was discovered. Possible reasons for this putative decline are unknown.
1974. Collins, Joseph T.. Amphibians and Reptiles in Kansas. University of Kansas Museum of Natural History Public Education Series. (1): pp. 283 pp.
1975. Plummer, Michael V. Population ecology of the softshell turtle, Trionyx muticus. Doctoral Thesis, University of Kansas. : pp. 173.
1977. Plummer, Michael V. Reproduction and growth in the turtle, Trionyx muticus. Copeia. 1977(3): pp. 440-447.
1977. Plummer, Michael V. Activity, habitat and population structure in the turtle,, Trionyx muticus. Copeia. 1977(3): pp. 431-440.
1982. Collins, Joseph T. Amphibians and Reptiles in Kansas, 2nd Edition. University Press of Kansas, Lawrence. Pp. 356.
1993. Collins, Joseph T. Amphibians and Reptiles of Kansas. University Press of Kansas, Lawrence, Lawrence. Pp. 397.