Overview of the natural history of Madagascar's endemic tortoises and freshwater turtles: Essential components for effective conservation

Madagascar had seven endemic chelonian species, including six tortoises and one aquatic turtle. The now extinct tortoises species, Aldabrachelys grandidieri and Aldabrachelys abrupta, as well as the extant species, Astrochelys yniphora, Astrochelys radiata, Pyxis planicauda, and Pyxis arachnoides, all occurred in the arid bush and in the mosaic of dry forests and wooded savannahs from south to northwestern regions of the island. The aquatic Madagascar Big-headed Turtle, Erymnochelys madagascariensis, occurs in rivers and large lakes in western Madagascar. These species all have delayed maturity offset by a prolonged reproductive lifespan. They also have a moderate annual reproductive output that includes multiple small clutches of eggs within a season, thus their intrinsic population growth rates are low. The last two decades have brought an increased under-standing of the demographic vulnerability of Madagascan chelonians to overexploitation. Particularly significant are the drivers of population dynamics relating to adult mortality and fecundity. The maximum level of harvest that their populations can sustain is low and is already greatly exceeded in most locations. This is the point at which the design of sound conservation strategies is crucial; increased integration of the natural history of Madagascan chelonians in conservation strategies could significantly improve their effectiveness. (Résumé d'auteur