Bio Facts: Turtle, Arrau
Arrau Turtle or Giant South American River Turtle
Caribbean drainages of Guyana and Venezuela and in the upper Amazon tributaries in northern Bolivia, northeastern Peru, Colombia, Venezuela, and northern Brazil. It is also occasionally found on Trinidad, especially after floods of the adjacent mainland Orinoco River.
It inhabits larger freshwater rivers and their tributaries (both blackwater and whitewater) and adjacent lagoons and forest ponds.
This is the largest river turtle in South America. It has a broad, domed and streamlined carapace for active swimming in moderate river currents. The color may be influenced by the algae that is attached to it, but is usually olive green to brown in color. It has a long neck which can be withdrawn horizontally within the shell, leaving it partly exposed, rather than retracting it in a vertical ‘S’ bend as in most other turtles.
In the wild they eat fruits, flowers, roots, and soft vegetation of aquatic plants and also those of the flooded riverine forests during the wet season. In the Zoo they are fed a scientifically developed, commercially available turtle food and assorted fresh fruits and vegetables.
IUCN – Lower Risk, Conservation Dependent; CITES – Appendix II
This species is mainly herbivorous, feeding on aquatic vegetation and plant matter that falls into the water. However, it is also known to be somewhat opportunistic, feeding on small, slow-moving prey and carrion.
Mutual cleaning behavior between individuals of this species has been observed. One turtle will position itself at right angles to a second turtle and use its jaws to pull algae from its shell. The turtles will then switch positions.
Breeding behavior has been well documented. Copulation occurs in the water, and the females then begin a period of basking for as much as six or more hours a day, presumably hastening egg development. After several weeks of this, they enter phase two where they retreat into the water after sunset but only for a few hours. Then they emerge to lay eggs in groups; the first nights may only be used for exploring the beach with actual nesting occurring a few nights later.
Nesting occurs at night, but may extend past sunrise during the dry season or low water season. Females lay from 61 to 172 leathery eggs per clutch. Large groups of females return to the same sandy riverbanks and sandbars every year to nest in groups that are thought to decrease loss of eggs to predators due to the shear numbers present. The eggs take an average of 59 days to hatch, timed to avoid the rising of the rivers which will drown any unhatched turtles. As with most turtles, the sex of the hatchlings is determined by the average temperature at which they are incubated – females develop at higher temperatures and males develop at lower temperatures.
P. expansa is belongs to a group of turtles called Pleurodira. This group consists of southern-hemisphere turtles also called side-necked (or sideneck) turtles. In order to hide their heads in their shells, they must fold their necks to one side, instead of withdrawing them directly under their spines as in most other turtles and tortoises do.
This is the largest species of side-necked turtle.
P. expansa parts and products are used in traditional medicines and cosmetics. Fat and egg shells are used to treat 16 different diseases, including rheumatism, bleeding (wounds), arthritis, tumors, inflammation, cellulite, acne, blemishes and scars. Turtle fat is the main product sold. Fat is used to make a topical rub for wounds and aching muscles. This product can be taken orally for some illnesses. Soap is also produced from fat and has been used for treating acne and scars.
The demand for these products is unknown. However, the use of this species in folk medicine might have a considerable impact on wild population, and this must be taken into account for the conservation and management of this species.
Threats to this species include poaching of females, collection of eggs and hatchlings, accidental and intentional capture (for food and oil) of adult turtles by fishermen, urban and industrial development near nesting sites, and lack of conservation education. Logging and clearing of areas surrounding rivers and damming of rivers can cause the water cycle to be drastically altered. This can confuse the turtles’ natural seasonal cycle of nesting which is timed to the alternation of floods and low flows. In addition, premature rising of rivers can flood nesting sites causing reduced hatching success.
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 2 ºC, the ratio of males to females could be severely skewed, and a rapid rise of 4 ºC could possibly eliminate males altogether. Turtles are seen as indicator species that can reveal the effects of climate change on the natural world.
With high reproductive potential, the Arrau turtle is expected to be capable of rapid recovery in areas with limited human presence and an environmental management plan. The management plan implemented at Middle Orinoco River has included the protection of nesting beaches, a nursery program for the care and release of hatchlings, and an environmental education program for the public. It has resulted in the slowed decline of nesting turtles and a modest increase in total turtle numbers since 1992. In addition, research has showed that eggs in a clutch laid by one mother may have different fathers, which helps to increase genetic variation and reduces the prevalence of inbreeding defects that result from small populations.
Although Brazilian legislation forbids commercial use of wild fauna (Article 1 Law 5,197 January 3, 1967 and Article 29 of Law 9,605 February 12, 1998), products and derivatives made from tortoises and many other animals are commonly illegally traded in Belém, and sale of turtle and tortoise products occurs in many other Brazilian cities. This suggests that turtle and tortoises are used for commercial purposes throughout Brazil, and these activities may be expanding into urban areas.
Jacksonville Zoo History:
The protected Arrau turtle has been part of the Jacksonville Zoo’s animal collection since 2003.