The Spiny softshell turtle is one of the largest freshwater turtle species in North America. The common name, spiny softshell, refers to the spiny, cone-like projections on the leading edge of the turtle's carapace, which are not scutes (scales). These spines are more commonly found in males. Spiny softshell turtles have webbed feet, and their feet have three claws. Another distinguishing feature of softshell turtles is the presence of a fleshy, elongated nose. The carapace (the upper part of the shell) ranges from brown or yellow-brown to olive in color, while the plastron (lower part of the shell) is lighter, usually white or yellow. Hatchlings usually have dark spots on the carapace, but as females age, they frequently become darker in color, or their carapace becomes splotched. Males tend to maintain the same coloration pattern from birth. Coloration also varies between each subspecies, and the exact coloration can also depend on an individual turtle's environment. Spiny softshell turtles are cryptically colored, meaning that their coloration helps them blend in with their surrounding environment. Spiny softshells also have pale lines bordered by black lines running from their head down the side of their neck.
Spiny softshell turtles have a wide range, extending throughout much of the United States, as well as north into the Canadian provinces of Ontario and Quebec, and south into the Mexican states of Tamaulipas, Nuevo León, Coahuila, and Chihuahua. These turtles live in freshwater habitats including ponds, lakes, rivers, tributaries, and streams. They inhabit shallow water (less than 1 meter deep) but can also be found as far as 10 meters deep. They can be found in areas with varying levels of vegetation, and generally occur in more slowly-moving waters. Spiny softshells prefer waters with sandy bottoms as well as clean, sandy banks. Sandy environments are important for nesting sites, proper juvenile growth and development, and camouflage.
Spiny softshell turtles are aquatic and spend most of their life in the water. They lead a solitary life and are active during the day. Spiny softshells spend their days foraging or basking in the sun on river banks or logs. If disturbed, they will quickly retreat to the water or will burrow themselves in the sand or mud with only their heads visible. When foraging for food, they can either actively hunt prey or bury themselves in the sand and wait to ambush prey. Spiny softshells migrate between warm and cold seasons. In each season, turtles generally stay in a single zone, and they move more within their zone during warm months. During cold months, from October to April, they spend underwater burrowed in sand or mud in a state of dormancy (hibernation). Due to their skin Spiny softshells are able to breathe underwater and this ability helps them to survive during their hibernation time.
Spiny softshell turtles are predominately carnivores (insectivores, piscivores) and feed on a variety of food items. They will consume insects, crickets, worms, crayfish, fish, shrimps, and mussels. They may also eat algal stocks and other plant materials.
Spiny softshell turtles have a polygynandrous (promiscuous) mating system which means that both males and females have multiple partners in a single breeding season. They mate in mid-to-late spring in deep water. The male will nudge the female's head while swimming, and if she chooses to mate, the male will swim above the female without clasping her with his claws (unlike other turtles). A few months later, the female lays her eggs along a sunny sandbar or gravel bank in a flask-shaped cavity she has dug close to the water. The turtle nests more than once during a single season. She can lay between 9 and 38 round, calcareous-shelled eggs. The eggs are laid around July and September, and they hatch in the spring. Unlike in other turtles, in the Spiny softshell turtle, the gender of the hatchlings is not determined by temperature variations; it is determined by genetics. Hatchlings don't receive parental care and become reproductively mature when they are between 8 and 10 years old.
The main threats to Spiny softshell turtles include pollution, water diversion, fishermen, habitat fragmentation and shoreline development which disturb nesting sites. The nesting sites are also at risk of predation from animals such as coyotes, foxes, and raccoons. Spiny softshells also suffer from hunting for food and hatchlings are collected as pets.
According to IUCN, the Spiny softshell turtle is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
Spiny softshells are important predators in their aquatic ecosystems. Due to feeding upon various amphibians, insects, and fish. they control the numbers of these species’ populations throughout their range.