The Arrau turtle (''Podocnemis expansa''), also known as the South American river turtle, giant South American turtle, giant Amazon River turtle, Arrau sideneck turtle, Amazon River turtle or simply the Arrau, is the largest of the side-neck turtles (

Pleurodira The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. The division between these two suborders represents a very deep evolutionary divide between two very different types of turtles. The physical differen ...

) and the largest freshwater turtle in

Latin America Latin America or * french: Amérique Latine, link=no * ht, Amerik Latin, link=no * pt, América Latina, link=no, name=a, sometimes referred to as LatAm is a large cultural region in the Americas where Romance languages — languages derived f ...

. The species primarily feeds on plant material and typically nests in large groups on beaches. Due to hunting of adults, collecting of their eggs, pollution, habitat loss, and

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

s, the Arrau turtle is seriously threatened.

Range and habitat

Arrau turtles are found in the

Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technology c ...

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wor ...

and Essequibo basins in Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela and Guyana. On occasion, typically after floods, individuals turn up in

Trinidad Trinidad is the larger and more populous of the two major islands of Trinidad and Tobago. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is often referred to as the southernmos ...

. They are found in deep rivers, ponds, freshwater lagoons and

flooded forest Freshwater swamp forests, or flooded forests, are forests which are inundated with freshwater, either permanently or seasonally. They normally occur along the lower reaches of rivers and around freshwater lakes. Freshwater swamp forests are found ...

white- White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White on ...

, black- and clear-water.

Appearance

Arrau turtles can reach up to in weight and the

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

length is up to . Most individuals are considerably smaller with the average adult female having a carapace length of and the average adult male . In addition to an overall smaller size, males can be recognized by their longer tail and straighter carapace than the females. Arrau turtles are brown, gray or

olive The olive, botanical name ''Olea europaea'', meaning 'European olive' in Latin, is a species of small tree or shrub in the family Oleaceae, found traditionally in the Mediterranean Basin. When in shrub form, it is known as ''Olea europaea'' ...

-green, but the exact color varies depending on the algae growing on the carapace.

Behavior

Feeding

Adult Arrau turtles feed almost entirely on plant material such as fruits, seeds, leaves, legumes and algae, but may also take freshwater sponges, eggs and carcasses of dead animals (such as dead fish). Captives have been recorded feeding on meat. Juveniles feed on fish and plant material. The species is mainly active during the day.

Breeding and life cycle

When nearing the breeding season, Arrau turtles migrate to certain sites where the eggs are laid. In some locations nesting occurs in large groups on beaches, which reduces the risk posed by predators. Some beaches have as many as 500 nesting females. Mating occurs in the water. During and just before the nesting season the species frequently basks, typically in groups. It is suspected that the additional heat accelerates the

ovulation Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized ...

in the females. At other times the species is generally not found on land. When on land, it is usually very shy and retreats to the water at the slightest hint of danger. The female lays an average of 75–123 eggs (average varies depending on region), which are placed during the night in a deep nest that is dug on the beach. The eggs are laid during the low water season and hatch as the water starts to rise. If it rises too fast or too early, the nest is flooded and the young die within the eggs. As long as nests are not dug up by predators, the hatching success rate is usually high, averaging at 83%. The eggs hatch after about 50 days and the sex of the young depends on the nest temperature (females at higher temperatures, males at lower). When hatching, the young are around long and dart directly for the water, but they emerge to the attentions of many predators so that only about five percent ever reach the adult feeding grounds.The Simon and Schuster Encyclopedia of Animals When hatching, the females emit sounds which attract the young; they stay together for a period in the flooded forests. Vocalizations appear to play an important role in the social life of this turtle and in addition to the "connect to newly hatched young" sound, four primary sounds have been documented during the nesting season: one used during migration, one before basking, one when nesting at night and finally one when in the water after nesting. They can reach an age of 20 years or more in the wild, and captives have lived for at least 25 years. Based on certain scientific models it has been estimated that the largest individuals perhaps are as old as 80 years.

Conservation status

The Arrau turtle is widespread and was not considered threatened overall by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

in 1996 (the year of the last full review), but it has declined drastically, and a draft review by the

IUCN Species Survival Commission The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natura ...

—Tortoise and Freshwater Turtle Specialist Group in 2011 recommended that it should be considered critically endangered. The species is slow to mature; some have suggested that females reach maturity when 4–8 years old and others have suggested about 17 years old. Their social behavior, especially at certain nesting beaches, makes them and their eggs vulnerable to humans. In addition to being used for food, they are sometimes used in

traditional medicine Traditional medicine (also known as indigenous medicine or folk medicine) comprises medical aspects of traditional knowledge that developed over generations within the folk beliefs of various societies, including indigenous peoples, before the ...

. At the main known nesting beaches, it is estimated that the number of nests fell from 34,000 in 1963 to 4,700 in 1981. In the middle Orinoco River alone, it is estimated that as many as 330,000 nested in 1800, but less than half this number nested in 1945 and by the early 2000s (decade) it had fallen to 700–1300. In addition to hunting and collecting of their eggs, threats include pollution, habitat loss, and

s, which can cause flooding of nest sites. Several countries in their range have implemented laws protecting the species, but hunting and egg collection (even if illegal) continues. A number of conservation projects have been initiated. For example, 54 nesting beaches have been protected in Brazil, beaches used by more than 1,000 females are protected in Colombia, and since the mid-1990s many thousand eggs have been collected in Venezuela for safe incubation, the hatchlings "headstarted" (getting them through the most dangerous period) and then released. All species in the genus ''

Podocnemis ''Podocnemis'' is a genus of aquatic turtles, commonly known as South American river turtles, in the family Podocnemididae. The genus consists of six extant species occurring in tropical South America.

'' are listed on

CITES Appendix II CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...

. The slow growth limits its potential for major commercial

turtle farming Turtle farming is the practice of raising turtles and tortoises of various species commercially. Raised animals are sold for use as gourmet food, traditional medicine ingredients, or as pets. Some farms also sell young animals to other farms, e ...

. Nevertheless, about 880,000 turtles of various species were kept at 92 farms (both ones that are commercial and ones with conservation purpose) in 2004 in Brazil alone, and some of these keep Arrau turtles, also in semi-intensive farm systems.

References

External links

{{Taxonbar, from=Q2625714 Podocnemis Turtles of South America Fauna of the Amazon Reptiles of Bolivia Reptiles of Brazil Reptiles of Colombia Reptiles of Ecuador Reptiles of Guyana Reptiles of Peru Reptiles of Venezuela Reptiles described in 1812