Overview
The Madagascar Big-headed Turtle (Erymnochelys madagascariensis), known locally as the ‘Rere,’ is an ancient, critically endangered side-necked turtle endemic to the western waterways of Madagascar. As the sole living representative of the genus Erymnochelys and the only African member of the family Podocnemididae (whose other surviving members live in South America), it is a living biogeographical relic dating back over 80 million years to the separation of Madagascar and South America. Renowned for its enormous, heavily armored head, it is one of the world’s most threatened chelonians.
Biology and Physical Characteristics
Erymnochelys madagascariensis is the largest native freshwater turtle in Madagascar, sporting an elongated, relatively flat, dark brown to black carapace. Its most diagnostic anatomical feature is its disproportionately immense, heavily ossified head covered in hard, bony dermal shields, which is so large that it cannot be drawn into the shell; instead, like all pleurodires, the turtle folds its head sideways beneath the margin of the carapace. It possesses immense, crushing jaws powered by massive jaw adductor muscles, enabling it to easily pulverize thick-shelled freshwater snails, river clams, and crabs.
Behavior and Ecology
Rere turtles are predominantly aquatic and diurnal, spending extensive hours basking on emergent logs, sandbanks, or river rocks to elevate their body temperatures for digestion. Highly wary, they dive into muddy water at the slightest disturbance. Feeding occurs on the riverbed, where they use their crushing jaws to crack open mollusks and tear tough aquatic vegetation. During the dry season (October to January), females haul out onto isolated, clean river sandbanks to excavate nesting cavities, laying clutches of 10 to 30 brittle-shelled eggs.
Conservation and Human Impact
Ranked among the top ten most endangered turtles on Earth and listed as Critically Endangered on the IUCN Red List, the species has suffered catastrophic declines exceeding 80 percent. The primary driver is intense, unsustainable harvesting for human consumption: because wild turtles bask openly and are slow swimmers, local fishers easily catch them in gillnets, fish traps, and hooks to sell in rural food markets. Extensive deforestation leading to river siltation and conversion of floodplain lakes into rice paddies further degrades nesting sites. Pioneering conservation programs by Durrell Wildlife Conservation Trust employ community patrols and nest protection.
Interesting Factoid
The Madagascar Big-headed Turtle is the only member of its entire family found outside South America, carrying an 80-million-year-old genetic heritage that dates back to the time when dinosaurs roamed Gondwana.