Central American River Turtle

Dermatemys mawii It is a relatively large-bodied species, with historical records of 60 cm (24 in) straight carapace length and weights of 22 kg (49 lb); however, more recent records have found few individuals over 14 kg (31 lb) in Mexico or 11 kg (24 lb) in Guatemala. It has a low, flattened, smooth carapace with a median keel present in juveniles, it is usually a uniform brown, almost black, grey or olive in colour. The plastron is usually white to yellow, though may acquire substrate staining in some areas. In juveniles, a distinctive keel is found down the centre of the carapace, and the outer edges have serrations. These features are lost as the turtle ages. Its skin is predominantly the same colour as the shell, with reddish or peach-coloured markings around the neck and underside. Adult males can often be differentiated from females by yellow (although sometimes cream or reddish-brown) markings on the top of their heads, as opposed to the uniformly dull-coloured heads of females, and longer, thicker tails.

Dermatemys mawii lives in Atlantic-draining larger rivers and lakes in Central America, from southern Mexico through Belize to the Guatemalan-Honduran border. In Mexico it occurs in the states of Veracruz, Tabasco, Campeche, the north of Oaxaca, the north of Chiapas and the south of Quintana Roo, primarily in the hydrological basins of the Papaloapan, Coatzacoalcos and Grijalva-Usumacinta River systems. In Guatemala the species occurs from southern and central Petén Department, south to Lago de Izabal and the rivers which drain into it. The presence and status in the Río Motagua bordering Honduras was unknown in 2011. It is reasonably common in the Pasión River and its tributaries as well as several lakes in Petén as of 1998. It was once common in Lake Petén Itzá, but by 1998 had become rarer there. It is well protected in Yaxhá Lake. In 2007 it was found to occur throughout northern Petén in the area corresponding to the Maya Biosphere Reserve, with the researchers reporting that it was quite common almost everywhere, and extending the known distribution somewhat with the Río Azul in Mirador-Río Azul National Park and Playa Grande, Quiche. Based on an extrapolation of the turtle densities obtained in this survey, 4,081 turtles are estimated to currently exist within this area. …

Dermatemys mawii is a nocturnal, completely aquatic turtle that does not bask or leave the water, except to lay eggs. The most significant predator is the otter (Lontra longicaudis). Vogt et al. stated in 2011 that these otters are known to be able to keep turtle populations low in some cases by hindering recruitment, whereas Platt and Rainwater in 2011 claim that they are the first to register otter predation in this species, and note that because other otter species in Canada or Europe are not significant predators of other species of turtles and turtles are not believed to form a major part of the otter diets, they hypothesise that otter predation is not significant, and also state that while there was ample evidence for otter predation in one part of Belize, this was the only place they had seen it occur. Campbell in 1998 notes that the otter is itself not common enough for this to be an issue. Especially large juveniles and subadults are preyed upon by otters in Belize. Otter predation can be recognised by the manner by which they typically chew off the heads, tail and limbs, sometimes slurping out the entrails, but leave the shell intact. The crocodiles Crocodylus moreletii and C. acutus usually feed on juveniles and hatchlings, or intermediate-sized turtles. Crocodiles crush the shell and swallow the turtle whole. …

The specific name, mawii, is in honour of the collector of the type specimen, Lieutenant Mawe of the British Navy. This species is usually vernacularly called tortuga blanca in Spanish, because it can be readily distinguished when prepared as food. When the meat of this turtle is cooked, it turns a white colour, unlike the more common turtle meat (Trachemys scripta), which colours dark.