Smooth Softshelled Turtle

Apalone mutica

Excerpted from: Animal Diversity

  Description

Smooth softshell turtles are medium to large freshwater turtles. Females have a back shell that is 6-14 inches long. Females are larger than males, who have a shell that is 5-7 inches long.

Like other softshell turtles, smooth softshell turtles have a carapace that is covered by skin instead of the hard scutes commonly observed in other turtle species. The carapace is ovoid and lacks spines on the front edge. The coloring of the carapace ranges from olive to orange. Females typically have a tan or brown carapace, while males have a brown or gray carapace. Both sexes have dark markings (spots, streaks, or blotches) on their carapace, although females typically have a blotchier pattern.

The plastron is light (white or gray) with no markings, and the underlying bones are visible. Dorsal coloration of an individual's head, limbs, and tail are similar to that of its carapace. A cream or orange line bordered in black extends from the back of each eye to the neck. Juvenile smooth softshell turtles do not differ in coloration from adults. Hatchlings have a brown or olive carapace with many markings on the carapace.

Smooth softshell turtles have a tubular snout with round nostrils that are usually positioned inferior, and they lack a septal ridge. Male smooth softshell turtles have thicker tails than females, a trait commonly observed in turtle species. In males, the anal vent is located near the tip of the tail, while in females, the anal vent is usually located near the edge of or under the carapace. Female smooth softshells have longer hind claws than males, which have longer foreclaws than females.

  Lifespan

Unlike many other species of turtles, Smooth Softshell Turtles do not form growth annuli on their shells, which make them very difficult to age in the field. The lifespan of this species is unrecorded. Individuals in captivity have lived over 11 years, and they are believed to be capable of living 20 years.

  Behavior

Smooth softshell turtles are the most aquatic of all North American softshells. Behavioral and morphological adaptations permit their aquatic nature. Smooth softshell turtles are able to remain submerged for extensive periods of time, which is made possible in part by their long neck and snout. They often bury themselves in the substrate of a body of water deep enough so their snout just barely reaches the surface. To achieve this position, a smooth softshell turtle pushes itself head-first into the sediment; it pulls itself with its front limbs while pushing with its hind limbs. When its body is positioned tilting downward toward the front, it stirs up the sediment. The falling material covers the turtle so only its head is visible.

Smooth Softshell Turtles hibernate by burying themselves in substrate underwater. They emerge from winter hibernation in May in northern areas of Wisconsin. Activity of smooth softshell turtles is typically observed from May through September. After emerging from hibernation, Smooth Softshell Turtles are often observed basking on sand bars or in shallow water between 7am to 5 pm. Sandy and muddy bars within a few meters of the water's edge are preferred basking sites, although logs and rocks near the water may also be used. When basking, smooth softshell turtles extend their neck and tuck their limbs into their shell.

  Communication

Smooth softshell turtles primarily interact through visual and tactile cues. When seeking out mates, males physically investigate females. Although little information was found regarding perception and communication by this species.

  Diet

Smooth softshell turtles are carnivorous, eating a variety of organisms including fish, amphibians (adults and larvae), arthropods, spiders, snails, mollusks, isopods, millipedes, and worms. Although the Smooth Softshelled Turtle is a dietary generalist, it can be classified as an insectivore. Arthropods typically consumed by Smooth Softshell Turtles are aquatic. Although primarily carnivorous, Smooth Softshell Turtles occasionally eat vegetation such as algae, potatoes, seeds, stems, mulberry, fruits, and hard nuts.

Further Reading:

 Beavers — Nature's Hydrologist, Part 2
 Garter Snakes — The Gardener's Friend
 Wisconsin Native Salamanders
 Goundhog or Woochuck: All The Facts
 Voles, Both The Good and The Bad