Calamus Swamp is a nineteen-acre public preserve near Circleville, Ohio, protecting a natural kettle lake and wetland that is the only known naturally vegetated, undisturbed kettle lake in central Ohio. Its basin was created during the last ice age by the glacier that once covered about two-thirds of the state. After Ada May Burke and Sally V. May received the land, they donated it to Columbus Audubon for public preservation. The swamp sustains a distinctive wetland plant community and provides habitat for migrating water birds, mammals such as raccoons and white-tailed deer, and aquatic life including Ohio fairy shrimp, giant water bugs, pond snails, and several kinds of leech.