The semiaquatic Smooth Softshell is characterized by a short tail, an upper shell with flexible, soft edges, a soft lower shell much smaller than the upper shell, uniform, patternless limbs, and a lack of bumps or tubercles along the front edge of the upper shell. The upper shell is olive to light brown with a pattern of darker dots or dashes (males) or blotches (females) and a marginal dark line. The lower shell is white or light gray. The head, limbs, and tail are olive to light brown above and white or light gray below. A black-bordered yellow or white line extends through the eye on each side of the head. Smooth Softshells have a tubular snout with round nostrils lacking septal projections (ridges extending from the inside midline into the nostril space). Males have longer tails, with the anal opening near the tip. Adult females have a mottled pattern on the upper shell and grow much larger than males.
Adults normally 115-306 mm (4½-12 inches) in carapace length. The largest specimen from Kansas is a female (KU 218796) from Osage County with a carapace length of 285 mm (11¼ inches) collected by John Powell and Beverly Downing on 9 June 1991. The maximum carapace length throughout the range is 355.6 mm (14 inches) (Powell et al., 2016).
Smooth Softshells are highly aquatic and found in rivers and large streams with sandy or muddy bottoms. 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 occurs statewide.
Plummer (1976, 1977), Plummer and Shirer (1975) and Fitch and Plummer (1975) have studied the Smooth Softshell on the Kansas River in Douglas County, and much of the information on habitat and breeding in Kansas is from their work.
This turtle prefers the sand or mud bottoms of moderate to fast flowing streams and rivers, rarely straying far from water except to bask and nest. It is active in northeastern Kansas from April to October, basking on sandbars, mud flats, steep mud banks, and logs along rivers. The Smooth Softshell avoids open water. During warm summers, when water levels are low, this turtle may become inactive.
It is apparently not territorial. The slightest disturbance will send these turtles scurrying into the water, where they may surface and float downstream to escape enemies.
During the night, this species rests buried in mud or sand below the water at a depth that allows its long neck to extend to the surface for air. These turtles are active during daylight, basking and foraging for food. They spend the winter months burrowed deep in the mud on the bottoms of rivers and streams.
Plummer (1977) estimated a population density of 1,900 turtles of this species in a one-mile stretch of the Kansas River in Douglas County. Capron (1987) estimated 500-700 Smooth Softshells per river mile in the lower Arkansas River valley.
This turtle mates during April and May and again during the fall. Courtship and mating take place in the water with much chasing of females by the males. The male maintains an extended neck while pursuing the female, frequently probing with his head under the sides of her shell. If the female is receptive, she remains passive and the male mounts her. If she is not receptive, she will bite the edges of the male's shell. The male mounts the female in the water but does not grasp her shell like some other turtles. Instead, he swims with the female during copulation.
Nesting reaches a peak during late May and June, when females emerge from the water to dig holes on high open sandbars. The number of eggs per clutch is 3 to 25 with an average of about eleven in Kansas; the number produced by a female increases with her size. The round, hard-shelled eggs hatch in the nest in 2- 2½ months, and the emerging young orient toward the light of flat open areas such as rivers. Adult male Smooth Softshells mature at four years of age, whereas females reach maturity at an age of six to nine years. Capron (1987) reported that this turtle nests during the first two weeks in June in the lower Arkansas River valley.
The Smooth Softshell is carnivorous, feeding primarily on insects, but it will also eat fishes, frogs, tadpoles, salamanders, crayfishes, snails, and worms. Plummer and Farrar (1981) showed that male turtles fed primarily on terrestrial insects, whereas female turtles ate mostly aquatic insects, and concluded that this difference was due to habitat preference, since males spend more time on or along shorelines than females. This turtle is a rapid swimmer, easily catching moving fish.
Raccoons and skunks relish the eggs of this turtle. The young are preyed upon by large fishes, other turtles, snakes, large birds, and various mammals. Heavy egg mortality occurs at high water levels during flooding (Plummer, 1976). In Kansas, people are the chief predators of full-grown Smooth Softshells. Capron (1987) expressed concern over the destruction of nesting habitat by offroad vehicles that damaged sandbars along the lower Arkansas River.
The Smooth Softshell was first reported from Kansas by Cragin (1880) where E. A. Popenoe observed it
in the Blue and Kansas rivers in the vicinity of Manhattan. The earliest known specimen (MCZ 4843) was collected at Manhattan, Riley County, by Francis W. Cragin on 16 September 1880 (as determined from the MCZ catalog).
This species exhibits a timid and gentle disposition when handled rarely attempting to bite.
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 (Fitch and Plummer, 1975; Plummer, 1975, 1977, 1977) and most of our information on the natural history of this species are due to his efforts.
The remaining known occurrences are widely scattered across the state. It is not a turtle that is observed (with confidence) without considerable work.
Cornelius Rogers took this species on a sandbar at the junction of a small creek and Medicine River, a little less than 5 miles southeast of Lake City, Barber County, Kansas, on August 30, 1934. Another was taken on a bank of Salt River just south of Aetna in the same county on April 21, 1934. On May 25, 1934, an example was secured 6 miles east of Turon, Reno County, Kansas, in a shallow sand-bottomed, algae-filled pasture streamlet (Burt, 1935).
Smooth Softshells may be taken year-round. The daily creel limit is eight turtles, single species or in combination (with Spiny Softshells and/or Snapping Turtles). The possession limit is three creel limits. A valid fishing license is required (unless exempt [e.g. < 16 years of age]). Legal equipment: hand, hook and line, setline, hand dip net, seine, turtle trap, or gig.
The Smooth Softshell can remain submerged in water for long periods due to its ability to remove oxygen from water through the membranes of its mouth.
References
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