The spiny softshell turtle is mainly carnivorous, feeding on crustaceans such as crayfish, as well as insects, small fish, worms, molluscs, tadpoles and frogs (1) (4) (5) (7) (9). It also occasionally eats some plant material, though possibly by accident (7). The spiny softshell turtle may actively hunt along the bottom of its watery habitat, searching for prey beneath objects or in clumps of vegetation, or it may conceal itself in the bottom mud and ambush passing prey (5).
This species spends almost its entire life in water, and often lies buried in the soft bottom with only its head and neck protruding into the water column. The spiny softshell turtle often buries itself in shallow water where its nostrils can reach the surface (2) (4) (7), but it will also bury itself in deeper water (4) (7). This turtle has a remarkable ability to extract oxygen from the water through its skin, allowing it to stay underwater for extended periods (4). The spiny softshell turtle also frequently basks on shore, on floating logs or on rocks, helping it to regulate its body temperature (5) (8) (9).
In parts of its range, the spiny softshell turtle hibernates in winter, burying itself in the bottom substrate in areas of deep, well-oxygenated water where it is at less risk of freezing (3) (5) (8). In Canada, this species hibernates for around six months of the year, typically emerging again in early May (5).
The spiny softshell turtle usually mates in the spring, with most nests being built around June and July (1) (3) (7) (8) (9). The female typically digs the nest in an open, sunny area of sand, gravel or soil close to water (5) (8) (9), and the eggs have hard shells which help to prevent them drying out (3). Each clutch consists of around 4 to 32 white eggs (5) (7), and females may sometimes lay two clutches a year (1) (7) (8) (9). The young turtles hatch from August to October (5) (7) (9). Unusually among turtles, the sex of the spiny softshell turtle hatchlings is not dependent on the temperature at which the eggs were incubated (4) (7) (10).
The male spiny softshell turtle is reported to reach sexual maturity at a shell length of just 9 to 10 centimetres, whereas the female matures at a shell length of around 18 to 20 centimetres (5), when it is approximately 12 years old (3) (5). The eggs and young of the spiny softshell turtle are vulnerable to a range of predators, including raccoons and foxes, as well as to infestation by fly maggots (3) (5) (8). However, adults of this species have few natural predators and are thought to potentially live to over 50 years old (5).