Ornate Box Turtles (Terrapene ornata) copulating in water: an incidental observation or ancestral behavior

Abstract

Herein, we report the first observation of the terrestrial Ornate Box Turtle (Terrapene ornata) copulating in water. To understand whether such an event reflected an isolated incident, we compiled observations reported in the literature of copulatory behaviors in water for other North American turtles. Our literature review revealed that other species of box turtles in North America, the Coahuilan Box Turtle (Terrapene coahuila) and Gulf Coast Box Turtle (Terrapene carolina major), occasionally also copulate in water. The vast majority of turtles in North America copulate in water, as most are semi-aquatic, including all species with observations in the Emydidae family. We did not find observations for water copulations in tortoises (Testudinidae), the most terrestrial group of turtles in North America. Although Ornate Box Turtles are terrestrially adapted, box turtles are within the family Emydidae, the pond turtles. Copulation in this fluid medium for terrestrial species might aid in the reproductive process with increased buoyancy and stability counteracting the high dome-shaped carapace that likely hinders copulation on land. Such a behavior also might help conceal individuals from predators or conspecific males that might disrupt copulating individuals. If ponded water is available within habitats for these terrestrially adapted box turtles, we predict underwater copulatory behaviors might be more common than recognized and remain undetected due to the inconspicuous nature of locations and rarity of ponded water in such habitats.