Aquatic Box Turtle

Terrapene coahuila

Description

This uniformly colored species is the only truly aquatic North American box turtle. Its elongated, narrow carapace, which grows to 6.6 in (16.8 cm), is domed but flattened on the top. The carapace is brown to olive green and lacks any pattern. The plastron is large and well-developed with no posterior notch on the anal scutes. The plastron is yellow to olive green with dark seams and some dark flecks on the scutes. The grayish-brown to olive head is large with a strongly hooked and notched upper jaw. The limbs, neck, and tail are also grayish-brown to olive. The five fore-toes and four hind-toes have little webbing. The plastron of the male is concave; the female plastron is convex or flat. The male iris is brownish and flecked with yellow, and the female's is yellow and flecked with brown. Her carapace is higher than the male's, and her tail is shorter and less thick.

Behavior

Mating has been observed during three seasons: fall (September and November), winter (December) and spring (March-May). During courtship, the male pursues the female with his head extended, bumping her shell with his carapace. Copulation occurs in or out of water. The May to September nesting season may produce several clutches of one to four elongated eggs. Hatching occurs in late summer or early fall. Hatchlings are more brightly colored than adults with yellow and black spots on the carapace. The aquatic box turtle is omnivorous and feeds on both land and in water. Its diet includes insects, crustaceans, snails, and small fishes. In captivity it will eat fish, worms, insects, lettuce, and fruits. It is an active forager that hunts for its prey, but it will also scavenge killed prey. The home range is small, comprising only 27.3 yds (25 m) in diameter with population densities of up to 156 adults per hectare (1 hectare = 2.471 acres) of marsh. The turtles spend much of their time buried in the mud bottom or lying under overhanging grasses. It is active all year but less active in cooler temperatures. Unlike all other species of box turtles which have difficulty submerging, the aquatic box turtle can submerge with ease and remain under water for considerable periods. Scientists speculate that as the Cuatro Cienegas land basin was subjected to more human activity, Terrapene coahuila was able to adapt to a water environment.

Habitat

The aquatic box turtle occurs is shallow waters with soft bottoms and abundant sedges, water lilies, and reeds. It prefers the slow currents of streams, ponds, and marshes with shallow water, a mud bottom, and dense vegetation.

Distribution

T. coahuila is restricted to the Cuatro Cienegas basin of Coahuila, Mexico.

Threats

T. coahuila is endangered because of loss of habitat in the rapidly developing Coahuila state of Mexico. Industrialization boomed in the 1930s and 1940s, and the industrial demand for water caused many natural ponds to dry up, resulting in the extinction of some fishes and threatening many aquatic species.

Conservation and Recovery

The primary need for the aquatic box turtle is preservation/restoration of wetlands. A long term strategy for preventing drainage of wetlands is essential in the Cuatro Cienegas basin. Successful captive breeding programs are being conducted at the Jersey Wildlife Trust and the New York Zoological Society, but reintroduction programs cannot be established without suitable habitat.

Contact

Instituto Nacional de Ecología
Av. Revolución, 1425
Col. Campestre, C.P. 01040, Mexico, D.F.
http://www.ine.gob.mx/

References

Behler, J. L. 1971. "Coahuilan box turtle Terrapene coahuila." Animal Kingdom 74:33.

Brown, W. S. 1974. "Ecology of the Aquatic Box Turtle, Terrapene coahuila (Chelonia, Emydidae) in Northern Mexico." Bulletin Florida State Museum Biological Sciences 19:1-67.