Yellow-headed sideneck turtle  (Podocnemis unifilis)

The yellow-headed sideneck turtle is classified as Vulnerable (VU) on the IUCN Red List (1) and is listed on Appendix II of CITES (3).

The yellow-headed sideneck turtle (Podocnemis unifilis) gets its name from yellow spots on the olive green to brown head, which are most obvious in young turtles, and fade to almost nothing in females, but remain present in males throughout life. The carapace is domed with a raised ridge in the centre, known as a keel. The plastron is yellow and sometimes has dark blotches. The head is long with a distinct snout, and there is usually a single barbel on the chin. This turtle belongs to the suborder Pleurodira, which contains the side-necked turtles, and has a long neck which can be withdrawn horizontally within the margins of the shell, leaving it partly exposed, rather than retracting it in a vertical ‘S’ bend as in turtles of the suborder Cryptodira (4).

This turtle is primarily found in the Amazon and Orinoco river systems in northern South America, including Venezuela, eastern Colombia, eastern Ecuador, northeastern Peru, the Guianas, Brazil, and northern Bolivia (5).

The yellow-headed sideneck turtle is found in calm waters and will occupy flooded forests, swamps and lagoons during high water and riverbeds in the dry season (2).

Male yellow-headed sideneck turtles court females by nipping at their feet and tails. During the evening, two weeks after mating (4), the female lays an average of 20 to 30 eggs in a fairly shallow nest (6), and these incubate under the heat of the sun for two months. The sex of the hatchlings is determined by the temperature at which they incubate. Eggs incubated below 32 degrees Celsius will hatch as males, and those incubated above 32 degrees Celsius will be females (7). Just a few days after hatching, the young turtles begin to forage for food alone. Food includes vegetable matter, grasses, fruits, leaves, carrion and molluscs. They are at risk of predation by humans, birds, snakes, large fish, frogs and mammals (4).

The yellow-headed sideneck turtle is diurnal and is most active in mid-morning and the afternoon. Groups of turtles can be seen basking in the sun on logs or stones in the middle of rivers, and they may also lie on the shore. As ectothermic (cold-blooded) animals, this behaviour functions to warm their bodies (2).

The greatest threat to this species is hunting by indigenous people known as Yekuana Indians, as they previously regularly consumed the meat and eggs of this species. The number of poachers is thought to have increased in recent years, as demand for both turtle eggs and turtle meat increases (8).

Climate change can potentially threaten turtle species as the sex of offspring is determined by the temperature at which they are incubated. Should the temperature rise by two degrees Celsius, the ratio of males to females could be severely skewed, and a rapid rise of four degrees Celsius could possibly eliminate males altogether. Turtles are seen as ‘indicator’ species that can reveal the effects of climate change on the natural world (9).

As the main consumers of yellow-headed sideneck turtles, the indigenous Yekuana Indians are now trying to hunt the turtles sustainably. They have implemented a conservation program for the 12 main nesting sites of the turtle along the de Ninchare River and these areas are now protected from poachers by armed guards. Other conservation initiatives include rescuing clutches that are at risk of being flooded by rising rivers, as well as rearing yellow-headed sidenecked turtles commercially (2).

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

For further information on the yellow-headed sidenecked turtle see:

• The Food and Agriculture Organization of the United Nations:
  http://www.fao.org/docrep/T0750E/t0750e09.htm

For more information on the possible impact of climate change see:

• Impact of Climate Change on Life and Ecosystems: Turtles and Global Climate Change:
  http://geochange.er.usgs.gov/sw/impacts/biology/turtles/