While the species is highly herbivorous, river cooters will eat anything, plant or animal, dead or alive. Diet seems to be determined by available food items. While some writers feel that these turtles will not eat meat, predatory behavior has been observed. Although this animal cannot swallow out of water, it will leave the water to retrieve a tasty bug or worm, returning to the water to swallow. Cooters will also enthusiatically chase, kill and eat small fish. They have also been observed eating carrion found along the river's edge. River cooters have tooth-like cusps in the upper jaw, probably an adaptation to aid in eating leaves and fibrous vegetation. Their primary diet would include a wide variety of aquatic plants, and some terrestrial plants that grow near the water's edge. They will happily take fallen fruits as well. In captivity, any kind of plant will be eaten, and some "meats", too. Always keep calcium available in a separate form, such as a cuttlebone, so that the turtle can self-regulate calcium intake.