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Turtles in Trouble

Top_25+_Turtles_in_Trouble_2011

Turtles

Turtles in Trouble: Top 25+ Endangered Tortoises and Freshwater Turtles—2011Central American River TurtleDermatemys mawii Gray 1847; Family DermatemydidaeNorth / Central America: Belize, Guatemala, Honduras (?), Mexico (Campeche, Chiapas, Quintana Roo, Tabasco, Veracruz)IUCN Red List: CR, Critically Endangered A2abd+4dCITES: Appendix IIThe last remaining representative of a turtlefamily dating back 65 million years, this uniquespecies reaches a carapace length of up to 65 cmand can weigh as much as 22 kg. It is entirelyaquatic, inhabiting rivers, lagoons, and otherlarge wetlands in southern Mexico, Guatemala,Belize, and possibly Honduras. It is so adapted toliving in water that it can barely move on land oreven hold its head up when out of the water. Thiswould seemingly present a problem for nesting,however, rather than emerging onto land to nest,females dig nests on beaches just below the waterlineduring floods, and the eggs only begin developingafter the water level drops. Like manyneotropical turtles, this species is crepuscularor nocturnal; often spending the day resting onthe bottom of rivers and lagoons, anywhere the water is deep.Well oxygenated water is preferred. The species is able to extractoxygen from the water via special vascular tissue in itsmouth, and is therefore able to remain submerged for a longtime without surfacing to breathe. During high water periodsanimals feed on shoreline vegetation. When water levels rise(3–8 m in some habitats) the turtles have access to a greatervariety of these foods in flooded forests.Laboratory incubation demonstrates that there is a widerange in incubation periods (115–223 days) of the eggs, whichcan be attributed to embryonic diapause and estivation. Embryonicdiapause (a temporary halt in development) allowsthe embryo to survive prolonged periods of cool temperaturesor low oxygen environments. Growth of the embryo only resumeswhen incubation temperatures are suitably warm andnests are no longer saturated with water. In addition, fully developedembryos estivate in the egg until hatching is stimulatedby an increase in soil moisture from the first summer rains.Hatchlings differ from adults in having the tip of their snoutbright orange; this color fades in the first two years to a paleyellow. Sex determination is temperature-dependent (as it isDermatemys mawii female from Guatemala. Photo by Melvin Merida, WCS.in many turtle species) with temperatures above 28°C producingfemales and temperatures of 25–26°C producing males.This species is highly esteemed for local consumption,and intensive collection, particularly for Easter festivals, hasdepleted populations severely across its range, to the pointwhere many local populations have been entirely extirpated.Many NGO's have been involved in helping to document survivalstatus and developing conservation solutions. The TurtleSurvival Alliance is currently conducting surveys throughoutBelize to assess status there, and is helping to develop a recoveryplan, Wildlife Conservation Society has been doing workin Guatemala, Conservation International and Conacyt havesupported population studies in Mexico, and the Turtle ConservationFund has provided support for several projects onthe species. Priority actions needed include local enforcementof existing protective regulations in the range countries, anddeveloping, coordinating, and implementing a comprehensiveconservation and recovery strategy for the species. This shouldinclude a consideration of reintroduction and headstarting tobolster remaining wild populations and, possibly, managedcommercial production systems to reduce poaching pressure.Distribution of Dermatemys mawii.Dermatemys mawii adult male. Photo by Gracia Syed.– 32 –

Turtles in Trouble: Top 25+ Endangered Tortoises and Freshwater Turtles—2011Madagascan Big-headed TurtleErymnochelys madagascariensis (Grandidier 1867); Family PodocnemididaeAfrica: MadagascarIUCN Red List: CR, Critically Endangered A4dCITES: Appendix IIThis evolutionarily distinctand biogeographically endemicfreshwater turtle is the onlyOld World representative of thefamily Podocnemididae (the remainingmembers of this familyoccur in South America). Asits common name suggests, thisspecies has a large head, whichin fully-grown adults showsa strong temporal helmet, orcasque. Its jaws are extremelypowerful with a slight hook attheir apex that may enhance itsability to feed on mollusks, fish,amphibians, and even birds;however, adults also commonlyeat seeds from trees and palmsas well as aquatic vegetation.Additionally, the eyes of thisspecies are situated forwardon the head; thus it needs onlyto extend a small portion of itshead above the water surface to observe potential prey,while the vast majority of its body remains submerged.The low flat profile and brown to slate-gray color of thecarapace makes this species look remarkably like a rock,additionally camouflaging it from potential prey and predators.This species was formerly widely distributed in westernMadagascar’s west-flowing rivers and floodplain lakes.However, its current distribution is extremely fragmenteddue to overexploitation. The species can be found in sevenprotected areas in Madagascar: Ankarafantsika, Baly Bay,and Bemaraha National Parks, and the new reserves of Manambolamaty,Ambondrobe, Menabe-Antimena, and Mahavavy-Kinkony.The réré, as the species is locally called,Distribution of Erymnochelys madagascariensis.Erymnochelys madagascariensis from Ankarafantsika, Madagascar. Photo by Anders G.J. Rhodin.is well known to the local people, as it is a large turtle, upto 50 cm carapace length and 17 kg; and due to its muchdesiredmeat, it is heavily collected for local and commercialconsumption. Increasing pressure from a dramaticallygrowing human population and changes in fishing habitstowards the use of nets, which results in substantial bycatchof this species, is having dramatic deleterious effectson its populations. In addition, locals also harvest eggs forconsumption, thereby reducing recruitment to the populations.In some areas, few adults remain, thus recruitment tothe population will be non-existent and the species’ survivalwill be dependent on the remaining juveniles survivinguntil adulthood.Survey data in the past three decades document an ongoingdecline of the species. Durrell Wildlife ConservationTrust and Conservation International, along with MadagascarNational Parks, have been involved in a program toprotect the species, reintroduce headstarted animals, andengage local communities at several sites in Madagascar.This conservation work has been closely integrated withinthe local culture and traditional conservation practices ofthe local communities, which has been a key to its success,with populations at Ankarafantsika as a result showingsome improvement in status. This program has alsoreceived support from the Turtle Conservation Fund, butneeds substantial increases in resources and intensity withan emphasis on reducing the harvest of adult animals.– 33 –

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