Dermatemys mawiiCentral American River Turtle

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Geographic Range

The Central American river turtle, Dermatemys mawii, can be found in Central America from southern Mexico as far south as northern and eastern central Guatemala, excluding the Yucatan Peninsula. There have also been sightings of D. mawii reported in northern Honduras (Ernst and Barbour 1989; Pritchard 1979).

Habitat

As long as there is an abundant food supply, D. mawii is not very particular about the environment it lives in. Individuals can inhabit just about any freshwater aquatic environment within their range, from deep, clean water bodies to muddy backwaters, oxbows, and temporary seasonal pools. Primarily, however, they live in large lagoons, lakes and rivers.

The presence of barnacles on the shells of some individuals indicates that salty environments do not pose a problem for this species of turtle and may show that D. mawii spends time in tidal areas near the mouths of large rivers (Ernst and Barbour 1989).

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

In adulthood, D. mawii can grow to be quite big. At its largest, this animal can measure up to 65 cm in length and it can weigh approximately 20 kg.

The smooth, somewhat flattened carapace, the top portion of the shell, has a uniform olive-gray color and is only slightly domed. The underside, or plastron, is 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 and 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. Additionally, juveniles have a carapace that is browner in color and a keel, which is absent in adults. 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.

The head of D. mawii is rather small, its skull lacking several features present in most turtles. The turtle's slightly upturned nose is large, and shaped like a tube with wide nostrils. It is a rather prominent feature of the turtle's face because it projects rather strongly from the front of the head.

The majority of the fleshy parts of the Central American River Turtle are olive gray, the undersides being white or pale gray. Near its upper surface, the organism is reddish brown to yellow in color while its sides typically remain the olive-gray of the shell. Adult male turtles have a triangular patch covering the whole upper section of the head that is golden yellow in color, as well as yellow markings on each side of the head. Females and turtles that have not yet reached maturity, have dull patches and side markings that are barely visible. Juveniles, however, display a yellow stripe extending backwards from the eye. The tail of D. mawii 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.

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 abbrasions 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.

The legs of D. mawii are dark gray with no patterns. The feet are fully webbed and broad, each with large scales on the outside edges (Dawson 1998; Ernst and Barbour 1989; Konstant 2000; Pritchard 1979).

  • Range mass
    0 to 0 kg
    0.00 to 0.00 lb
  • Average mass
    20 kg
    44.05 lb

Reproduction

Nesting occurs continuously from September to November during the time when the rivers the turtles live in swell considerably due to flooding caused by seasonally increased rainfall. This phenomenon helps D. mawii reproduce because it allows females to lay eggs in more secluded areas away from the normal river channel. Normally, females could not reach these areas by foot but because they are flooded with the excess rainwater, they are easy to swim to.

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.

Generally, D. mawii lays oblong eggs with white shells that are very thick and hard. Each clutch contains six to twenty eggs that are approximately 57-70 mm long and 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).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Lifespan/Longevity

Behavior

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.

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. As a result, 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 Central American River Turtle 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. This species of turtle is very passive and has a mild disposition. When handled, it will thrash its tail and limbs around vigorously but rarely bites.

The courtship and mating habits of D. mawii have not been described. However, because members of the opposite sex fight when kept together in captivity, it is thought to be a rather agressive process.

Eggs, hatchlings, and adults of this species are hunted and eaten by humans, crocodiles, raccoons, coati mundis, river otters and a number of wading birds (Ernst and Barbour 1989; Konstant 2000; Pritchard 1979).

Food Habits

The Central American River Turtle generally eats plants either submerged below the water or those that rise just above the water's surface. Typically, these include Russell river grass (Paspalum paniculatum), and fallen leaves and fruits from branches growing over the water.

Captured D. mawii will occasionally, however, eat fish. Juveniles in captivity tend to more readily accept animal matter as food which may show that young D. mawii are more apt to be carnivorous (Ernst and Barbour 1989; Konstant 2000; Poaceae 2000).

Economic Importance for Humans: Positive

The flesh of D. mawii is a high quality food source that can be obtained in high quantity from one turtle. Central American River Turtles eat aquatic plants that are of no use to humans and use them to produce turtle protein for human consumption. Not only could Central American River Turtles supply a valuable protein source if farmed successfully, they could also supply a valuable source of income for humans living near their habitat (Ernst and Barbour 1989).

Economic Importance for Humans: Negative

There are no known adverse effects of this species on humans.

Conservation Status

Because the meat of D. mawii is sold at markets near rivers for high prices, the turtles are highly sought after and have been over-exploited by hunters. The hunting problem is exacerbated by the fact that these turtles are easy to catch because of their passive nature. Legislation has been passed nationally and internationally to help D. mawii but enforcement of this legislation remains inadequate (Ernst and Barbour 1989; Konstant 2000; Pritchard 1979).

Other Comments

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 know by its Creole nickname, "hickatee." In other areas of its habitat it is know as "tortuga blanca" or "white turtle", either due to its pale undersurface or the color of its meat (Konstant 2000; Pritchard 1979).

Contributors

Heidi Lowry (author), University of California, Irvine, Rudi Berkelhamer (editor), University of California, Irvine.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Dawson, J. 1998. "The Turtle Pages - Anatomy of a Turtle" (On-line). Accessed November 3, 2000 at http://www.crosswinds.net/~theturtlepages/anatomy/skeletal.html.

Ernst, C., R. Barbour. 1989. Turtles of the World. Washington: Smithsonian Institution Press.

Konstant, W. 2000. "Hotspots: Features" (On-line). Accessed October 27, 2000 at http://www.conservation.org/Hotspots/reptile2.htm.

Poaceae, L. April 7, 2000. "Paspalum Paniculatum" (On-line). Accessed November 30, 2000 at http://www.hear.org/pier/papan.htm.

Pritchard, P. 1979. Encyclopedia of Turtles. Neptune, NJ: T. F. H. Publications, Inc..