Central American river turtles

(Dermatemydidae)

Class Reptilia

Order Testudines

Suborder Cryptodira

Family Dermatemydidae

Thumbnail description
This is a large aquatic turtle whose dark shell appears leathery in adults, whose plastron and bridge are both large, and whose head is relatively small with a pointed snout; a row of inframarginal scutes separates the scutes of the carapace from those on the plastron

Size
Up to 26 in (65 cm) and 49 lb (22 kg)

Number of genera, species
1 genus; 1 species

Habitat
Permanent rivers and lakes

Conservation status
Endangered

Distribution
Caribbean Sea and Gulf of Mexico drainages of Mesoamerica

Evolution and systematics

These river turtles (Dermatemys mawii) are most closely related to the mud and musk turtles (family Kinosternidae). The fossil record of this family is extensive, with the earliest material being from the Lower Cretaceous in Asia, and abundant remains in North and Central America, Europe, and Africa during the Tertiary. The Central American river turtle is also commonly known as hickety (Belize), jicotea, tortuga aplanada (Mexico), tortuga blanca (Mexico, Guatemala), and tortuga plana (Mexico). No subfamilies are recognized.

The taxonomy of this species is Dermatemys mawii Gray, 1847, South America (in error); restricted to Alvarado, Veracruz, Mexico, by Smith and Taylor, 1950.

Physical characteristics

These large turtles (up to 49 lb [22 kg]) have a low, dark, carapace that is unicarinate in juveniles, but smooth and leathery in adults. Females reach larger sizes than males. The posterior margin of the shell is smooth and not serrated. The yellow or cream-colored plastron is large, unhinged, and connected to the carapace by a broad bridge on which four or five inframarginal scutes are located (separating the plastral from the carapacial scutes). The snout is pointed, no chin barbels are present, and the toes are strongly webbed. The top of the head in adult males is yellowish and that in adult females and juveniles is gray.

Distribution

Atlantic lowlands from southern Veracruz in Mexico through the southern Yucatán Peninsula, northern Guatemala, and Belize.

Habitat

Permanent water in rivers and large freshwater lakes, occasionally entering brackish water as evidenced by the finding of barnacles on some individuals.

Behavior

This turtle is highly aquatic, is capable of remaining submerged for very long periods, and has a very difficult time moving on land. It is primarily nocturnal, but it can sometimes be seen basking at the surface of the water during the day. It does not bask out of the water.

Feeding ecology and diet

It is almost completely herbivorous, feeding on fruits (e.g., figs), aquatic grasses, and fallen leaves. Insects, fish, and mollusks are occasionally consumed.

Reproductive biology

Courtship and mating apparently occur from March to September, and nesting occurs primarily during the rainy season, from late September to December. However, nesting sometimes occurs from late August to March or April. Females produce one to four clutches per year, with two being usual. Nests are excavated in the soil, usually within 10 ft (3 m) of the water, and are often inundated by rising water. Eggs have been found to be viable after being submerged for up to 28 days. Eggs are brittle-shelled, oblong, 2.1–2.8 in × 1.2–2 in (54–72 mm × 30–50 mm), and weigh 1.2–2.5 oz (34–70 g). Clutch sizes range from two to 20, with eight to 14 being typical. Large females have greater annual reproductive potential than small females. Incubation requires seven to 10 months, and hatching occurs in late May through July, at the beginning of the next rainy season. The sex is determined by nest temperature during the middle third of incubation, with high temperatures producing females and low temperatures producing males.

Conservation status

Listed as Endangered on the IUCN Red List, as Endangered by the U.S. Fish and Wildlife Service, and in Appendix II of the CITES.

Significance to humans

Central American river turtles are intensively exploited for food by indigenous peoples throughout their range, even in areas where the species is legally protected. The flesh is considered a delicacy.

Resources

Books

Lee, Julian C. The Amphibians and Reptiles of the Yucatán Peninsula. Ithaca, NY: Comstock, 1996.

Polisar, John. "Effects of Exploitation on Dermatemys mawii Populations in Northern Belize and Conservation Strategies for Rural Riverside Villages." In Proceedings: Conservation, Restoration, and Management of Tortoises and Turtles: An International Conference, 11 to 16 July 1993, State University of New York, Purchase, New York, edited by Jim Van Abbema. Bronx, NY: New York Turtle and Tortoise Society, 1997.

Periodicals

Polisar, John. "Reproductive Biology of a Flood-Season Nesting Freshwater Turtle of the Northern Neotropics: Dermatemys mawii in Belize." Chelonian Conservation and Biology 2, no. 1 (1996): 13–25.

Polisar, J., and R. H. Horwich. "Conservation of the Large, Economically Important River Turtle Dermatemys mawii in Belize." Conservation Biology 8, no. 2 (1994): 338–340.

Vogt, R. C., and O. Flores-Villela. "Effects of Incubation Temperature on Sex Determination in a Community of Neotropical Freshwater Turtles in Southern Mexico." Herpetologica 48, no. 3 (1992): 265–270.

John B. Iverson, PhD