Madagascar big-headed turtle  (Erymnochelys madagascariensis)

Classified as Critically Endangered (CR) on the IUCN Red List (1), and listed on Appendix II of CITES (3).

Tortoises and turtles are among the oldest of all living reptiles having appeared about 250 million years ago. They have evolved little since then and their ancient appearance and unique biology fascinates biologists (4). The Madagascar big-headed turtle is, however, one of the most endangered turtles in the world, and is included on the Turtle Conservation Fund’s (TCF) top 25 endangered turtles list (5). This species has a hard, dark-brown coloured shell enclosing the soft parts of the body and, as its name suggests, a distinctively large head. Juvenile turtles have a delicate pattern of fine black lines on the shell, but these disappear with age. Its other common name, the Madagascar side-necked turtle also reveals a feature shared by other species in the Pleurodira sub-order: when the head is withdrawn into the shell, the neck bends sideways rather than straight back as in other turtles and tortoises (6). The neck is also long, and allows the turtle to draw breath at the surface of the water without exposing the rest of the body to potential predators (7).

This turtle is endemic to Madagascar and occurs in the western lowland areas of the island (2).

Inhabits large, freshwater areas such as permanent slow moving rivers, backwaters and lakes (2). Many hatchlings and juveniles move into smaller rivers and even rice paddy-fields where they grow quickly before returning to larger bodies of water to breed when mature (8).

This turtle occurs in freshwater areas and, like most other side-necked turtles, it is highly aquatic - rarely venturing onto land except to lay eggs, and preferring to bask on logs, rocks or banks surrounded by water (8). It is mainly herbivorous, feeding on plants and the fruits, flowers and leaves of plants overhanging the water. It has also been known to opportunistically feed on small vertebrates (7). Hatchlings and juveniles are predominantly carnivorous (8). Females produce eggs that are spherical to elongate shaped, with leathery shells (7). Normal clutch sizes are in the region of 10 to 25 eggs for a mature female (8).

This species is heavily exploited for food in Madagascar, where it is easily caught in nets, fish traps and by hook and line (8). It is also caught and exported illegally from Madagascar to Asia for the traditional medicine market. Furthermore, land development on Madagascar is a serious threat to this turtle, as it destroys its natural habitats. Clearing forests for agriculture and timber opens up Madagascar’s untouched habitat and leads to terrible erosion. Subsequent siltation of rivers and lakes renders the turtles even more susceptible to trapping (5).

The Madagascar big-headed turtle is protected from international trade by its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (3). In May 2003 the Turtle Conservation Fund (TCF) released the first ever list of the world’s top 25 endangered turtles, which included the Madagascar big-headed turtle (5). The TCF intends to cover a five year ‘Global Action Plan’ that includes captive breeding and reintroduction projects, trade monitoring, and establishment of rescue centres, local conservation plans and educational programs (5). The Durrell Wildlife Conservation Trust is also independently involved in the conservation and protection of this species (9). It is hoped that these measures will provide the protection that this species needs to survive in its natural habitat.

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on the Madagascar big-headed turtle see:

• Turtle Survival Alliance:
  www.turtlesurvival.org