Turtle, Central American River


Dermatemys mawii


Length – 25” (65 cm); weight - approximately 44 lbs. (20 kg); carapace - smooth, somewhat flattened and is a uniform olive-gray color; plastron - cream-colored, rounded at the front and serrated at the end; in adults, the carapace lacks a well-defined vertebral ridge running down its center, is smooth and unnotched around the outer edge; in juveniles of the species, this ridge is present as well as a notched posterior shell end that is somewhat outspread; juvenile carapaces are browner in color and keeled, which is absent in adults.; head is rather small, its skull lacking several features present in most turtles; nose is slightly upturned and large, and shaped like a tube with wide nostrils; skin is olive gray, the undersides white or pale gray; adult male turtles have a triangular, golden yellow patch covering the whole upper section of the head and yellow markings on each side of the head; females and sub-adults have dull patches and side markings that are barely visible; juveniles have a yellow stripe extending backwards from the eye; tail is thick and longer in males than in females. It extends past the edge of the back of the carapace in males and just barely to that edge in females; legs are dark gray with no patterns; feet are fully webbed and broad, each with large scales on the outside edges (Dawson 1998; Ernst and Barbour 1989; Konstant 2000; Pritchard 1979).

Family

Dermatemydidae

Order

Testudines

Class

Reptilia

Range

Central America from southern Mexico as far south as northern and eastern central Guatemala, excluding the Yucatan Peninsula.

Habitat

Primarily they inhabit large lagoons, lakes and rivers. As long as food is abundant, they also inhabit other freshwater aquatic environment within their range, from deep, clean water bodies to muddy backwaters, oxbows, and temporary seasonal pools.

Life Expectancy

Sexual Maturity

Females reach maturity at a length between 13.5” – 16.5” (34.2–42.0 cm), while males become mature between 12.9” – 15.2” (32.8-3

Diet

In the wild, they eat aquatic vegetation; in the Zoo they are fed a proprietary gel-based turtle food and fresh produce.

Status

IUCN – Critically Endangered; CITES – Appendix II; USFWS - Endangered

Behaviors

The most aquatic of all turtles, D. mawii spends the major part of the day either resting underneath the water, or floating on its surface, usually asleep. Much of its feeding and other activity goes on at night. It does not bask in the sun on top of logs and river banks as do most turtles. The courtship and mating habits of D. mawii have not been described. Because members of the opposite sex fight when kept together in captivity, it is thought to be a rather aggressive process. Nesting occurs continuously from September to November when the rivers swell considerably during the rainy season. This helps D. mawii reproduce; it allows females to lay eggs in more secluded areas inaccessible to turtles when the rivers are low and are away from the normal river channel. Once females have reached a shallow rivulet, they dig out a nest, lay their eggs, and bury them at the edge of the water under mud and decaying vegetation. Eggs are oblong with white shells that are thick and hard. Each clutch contains six to twenty eggs that are approximately 2.2” – 2.7” (57-70 mm) long and 1.1” – 1.3” (30-34 mm) wide. Because the life of this turtle is so completely aquatic (and therefore difficult to study), little else is known about its development and early life (Ernst and Barbour 1989; Pritchard 1979).

Adaptions

Because it is so well-adapted to its watery home, its limbs cannot support its own body weight, which makes most movements attempted on land very poorly coordinated. D. mawii has major difficulty walking on land for any distance as well as lifting its head. However, its swimming motions underwater are rapid and well-executed. Because of a highly adaptive breathing mechanism, it is only necessary for a D. mawii to surface periodically for air. It sucks water in through its mouth and draws out dissolved oxygen from the water by means of a highly perforated pharyngeal lining (just behind the nasal cavity). The used water is then expelled back through its nostrils. In muddy or cloudy water, the motion of the water moving in the mouth and out the nose is visible.

Special Interests

In addition to being smooth, the shell is quite thick and rather heavy. The bones that make up the shell can become so tightly fused together in older adults that the sutures, the structures that join the bones of the shell together, become almost invisible, even in dry, bony shells. Incredibly thin and almost membrane-like, the turtle’s scutes, keratin coverings over the bones that make up the shell, are very sensitive and prone to abrasions when in contact with hard surfaces. If, for example, the animal comes in contact with concrete, it will only be a short time before the animal has almost worn itself away to the bone. While the damage that can be done will be repaired to some extent, it will never completely heal and become smooth again, as it once was. Sheets of dead bone will be shed to reveal a pitted, but healed surface. The scute boundaries, like the sutures, become virtually invisible in adults. While at one time widespread, D. mawii is the sole living member of the primitive family Dermatemyidae, which first showed up in Asia during the Cretaceous period. By the Tertiary period, this family had spread into Europe, Africa, and North and Central America but eventually died out to the point that only one species remains. In areas of Belize, D. mawii is known by its Creole nickname, “hickatee.” In other areas of its habitat it is known as “tortuga blanca” or “white turtle”, either due to its pale undersurface or the color of its meat (Konstant 2000; Pritchard 1979).

Folklore

Conservation

D. mawii is perhaps the most endangered species, genus, and family of turtles in Mexico, and possibly elsewhere in its limited range. Currently the greatest threat to this species is the human over-consumption that has driven them to be threatened with extinction. Although some of the habitats where these turtles live have been degraded, over-exploitation started even before habitat degradation. Dermatemys are captured with nets, by free diving and by harpooning. Its sale has been illegal since 1975, but this has not done very much to reduce its capture. In Mexico, Dermatemys sold for up to US$10 per large animal (presumably over 22 lbs. (10 kg)) in 1979 (Alvarez del Toro et al. 1979); it is currently valued at over $40 per kg live weight in Villa Hermosa (Syed pers. comm. with PROFEPA wildlife inspectors in Tabasco 2005). In 1980 animals were still seen in the fish markets of Alvarado, Lerdo de Tejada and Minatitlan; today they are not sold openly in local markets. In Alvarado, their meat is frozen for sale and delivery is by request (Vogt pers. obs.). Turtle traders in Veracruz expressed concern about future supplies as long ago as 1970 (Mittermeier in Alvarez del Toro et al. 1979). Dermatemys are traditionally harvested for consumption in many areas of Belize (Moll 1986b, Polisar 1995). Dermatemys is similarily one of the most valued turtles in Peten, Guatemala, because its meat is considered a delicacy; animals continue to be hunted with nets, harpooned or collected by hand. At recent harvest rates, the species is expected to be driven inevitably to extinction (Campbell 1998). In addition, the depletion of Mexican populations and the high demand for the species in Mexico will inevitably invite smuggling from Guatemala and Belize. Dermatemys has been subject to legal protection in Mexico since 1927, as under the Mexican Constitution all natural resources belong to the Nation and can only be exploited with formal authorization/permits. Dermatemys was included in the Mexican Red Data List (NOM-059-ECOL 1994) as endangered, making all forms of harvest and exploitation illegal. However, very little is done to enforce the law and few people respect it (Vogt pers. obs.). In Belize, there is national legislation (Statutory Instrument No. 55, of April 1993) designed to control the level of harvest and establish some protected populations (Polisar 1994). The efficacy of this legislation needs to be evaluated and the nation-wide status of the species assessed. Dermatemys is protected under Guatemalan law (Campbell 1998) but exact details are not available. Laguna La Popotera, Veracruz, Mexico, was designated a RAMSAR site in 2005 with specific hopes of creating the first extensively managed wildlife reserve specifically for Dermatemys (Horne in litt. to TFTSG RLA, 27Jul 05). The species is present in Laguna del Tigre N.P. in Peten, Guatemala, and was recommended as a focal species for park management (Castañeda Moya et al. 2000). Currently there are several ex situ populations of this species with which viable breeding colonies can be established in different zoos and farms. Some of these ex situ populations are: Nacajuca, Tabasco, with 880 turtles, La Florida, Veracruz, with 45 turtles, the Veracruz Aquarium with 2 animals, Chicago Zoo with 2 animals, Detroit Zoo with 2 animals, Philadelphia Zoo with 9 specimens, and the Guatemala City Zoo with one animal. In 2004 a group for D. mawii conservation was established, proposing a program that includes raising the authorities’ and people’s awareness on the species, its captive conservation that includes the genetic management of the captive populations, evaluating the wild populations and their habitat, improved enforcement of existing legal protection, promotion of harvest management measures for sustainable use, and the creation of a reintroduction program. In summary, existing protective measures need to be implemented, populations inhabiting protected areas must be watched over carefully, and careful thought must be given to meeting some, if not all, of the intensive commercial demand for the species by sustainable production from farms.

Jacksonville Zoo History

This highly endangered turtle has been part of the Jacksonville Zoo and Gardens collection since 2003.

Exhibit

Range of the Jaguar