Broad-shelled long-necked turtle | |
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Brisbane City Botanic Gardens | |
Hunting fish at the Bronx Zoo | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Testudines |
Suborder: | Pleurodira |
Family: | Chelidae |
Genus: | Chelodina |
Subgenus: | Chelydera |
Species: | C. expansa |
Binomial name | |
Chelodina expansa (Gray, 1857) | |
Synonyms [1] | |
List
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Chelodina (Chelydera) expansa, commonly known as the broad-shelled river turtle, broad-shelled snake-necked turtle, [2] or giant snake-necked turtle [3] , is a pleurodiran freshwater turtle and is the largest of the long-necked turtles. [4] It is widely sympatric with the Murray River turtle and eastern snake-necked turtle. [5] C. expansa is listed as ‘vulnerable’ in South Australia and ‘threatened’ in Victoria. [4]
Broad-shelled river turtles are found throughout the Murray-Darling basin of southeastern Australia. A number of distinct populations are also found across areas of central and coastal Queensland. [2]
C. expansa is mostly found in turbid waters of depths greater than three metres. [4] It is mostly a river turtle, generally inhabiting permanent streams [2] but is also found in oxbows, ponds in floodplains, backwaters, and swamps [4] across its distributed region. The broad-shelled river turtle will tend to inhabit environments that are undisturbed and have moderate vegetation cover for nest construction. The turtle has shown a preference of aquatic habitats in structured environments, where submerged logs, root systems and dead trees occur. Factors such as shelter from predators and food availability may influence the habitat preference of C. expansa. Seasonal changes including water level and flow may also influence the selected the habitat. [4]
The broad-shelled river turtle has a broad, oval and flattened shell with a length of around 50 cm. [2] The carapace length is often greater in females than males. [4]
The turtle has a rich brown to blackish-brown carapace above, typically displaying fine dark flecks or reticulations, and a whitish or cream-colored belly. The plastron is narrow and the shell does not display any noticeable expansion anteriorly. The shell is usually twice as long as wide and is broadest at the level of the bridge. The head is broad and highly depressed and the eyes are directly dorsolateral. [2] When extended, the neck may be longer than the carapace. [4]
The broad-shelled river turtle is mostly active from Austral spring season (October) through to early autumn (April). The species tends to decrease in movement and feeding over the cooler winter months. [4] C. expansa is described to also show head bobbing and self-grooming actions. [6]
Chelodina expansa spends most of its time in water. [5] During periods when water levels are low, C. expansa will traverse over land to find other water sources. The turtle may also bury itself into mud and enter extended periods of aestivation until rain occurs and water levels increase. [5]
C. expansa usually nests during Austral autumn [2] or in early winter when soils decrease in temperature. [7] It will also sometimes nest during spring. Although the female broad-shelled river turtle will travel up to one kilometre away from the bank to lay her eggs, it is more common for them to nest within 100 m of the water's edge. Along the Murray River, nests are often constructed at the top of sandy ridges. [4] In Autumn nestings, temperatures in the nest will initially decrease and then remain low during the winter period before slowly increasing during spring to reach a maximum temperature during summer. [8]
The female turtle constructs a nest by excavating a nesting chamber with her hind legs to a depth of around 20 cm. She then deposits between 5 and 28 eggs before backfilling the nest with soil. The broad-shelled river turtle has shown a ‘body-slamming’ type behaviour when compacting nests. [9] This behaviour results in the formation of a hardened 'plug' which helps to seal the nest. These turtles will nest any time of the day or night with nesting being initiated by rain. Turtles tend to select nest sites that have higher sun coverage. The selection of nest sites is often a long way from the waters edge and this is seen as a behavioural strategy to minimise the risk of nest flooding.
Hatchlings are exposed to a number of challenges. [9] Incubation is exceptionally long due to inherently slow embryonic development, [7] averaging between 324 and 360 days. [4] Development is also delayed when the embryo enters two distinct periods of diapause. [4] [7] The primary diapause occurs inside the female before the eggs are laid. This form of diapause is known as pre-ovipositional embryonic arrest and is found in all turtles. [10] The secondary diapause is triggered by a drop in nest temperature and occurs after embryonic growth has resumed within the nest. [4] The young will generally hatch during spring. [2] Asynchronous hatching is most likely maladaptive in the natural environment. [7] Upon hatching, the young remain in the egg chamber awaiting heavy rain to trigger their release. The soil surrounding the nest, which becomes compacted and relatively hard during the long incubation, is softened by the rains and allows the hatchlings to dig their way out through the softened soil.
The broad-shelled river turtle is highly specialized and entirely carnivorous. [4] C. expansa primarily preys upon frogs, [11] crustaceans, aquatic insects, and small fish. [4]
The introduced red fox (Vulpes vulpes) and ravens (Corvus spp.) are the major threats to the nests of the broad-shelled river turtle. Predation of nests by foxes along the Murray River is in excess of 93% which means there is little recruitment of young turtles into an ageing population. As turtles are long-lived animals and adults are still commonly seen in the wild, this can lead people to falsely believe that the population is still healthy. Other nest predators include monitor lizards, ibis and feral pigs. Predation of nests is the main challenge for C. expansa, however it is thought that the turtle becomes aware of predators, mostly from olfactory and visual signs. Hatchlings face a variety of predators while they travel overland to water; these can include birds and lizards in addition to feral foxes and feral cats. Many young turtles also die from dehydration if they fail to reach the water in time, and some are killed whilst trying to cross roads. Once they reach the water, they may be eaten by fish and other aquatic predators. In the fragmented Queensland populations, the main predator of hatchlings is the spotted barramundi. [4]
The broad-shelled river turtle may be infected with adults of the parasitic flatworms D. pearsoni and D. megapharynx. These flukes appear to be host-specific and live in the intestines of C. expansa. [12]
For photographs and distribution maps of Chelodina expansa please see: https://commons.wikimedia.org/wiki/Category:Chelodina_expansa.
Chelidae is one of three living families of the turtle suborder Pleurodira, and are commonly called Austro-South American side-neck turtles. The family is distributed in Australia, New Guinea, parts of Indonesia, and throughout most of South America. It is a large family of turtles with a significant fossil history dating back to the Cretaceous. The family is entirely Gondwanan in origin, with no members found outside Gondwana, either in the present day or as a fossil.
The chicken turtle is a turtle native to the southeastern United States. It is the only extant member of the genus Deirochelys and is a member of the freshwater marsh turtle family Emydidae. The chicken turtle's scientific name refers to its extremely long neck and distinctive net-like pattern on its upper shell. There are three regionally distinct subspecies, which are thought to have evolved when populations became separated during periods of glaciation. These subspecies can be distinguished by their appearance; the western chicken turtle displays dark markings along the seams of its plastron, while the plastron of the Florida subspecies is a bright yellow or orange color. Fossil records show that the chicken turtle has been present in the region for up to five million years.
The loggerhead sea turtle is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 cm (35 in) in carapace length when fully grown. The adult loggerhead sea turtle weighs approximately 135 kg (298 lb), with the largest specimens weighing in at more than 450 kg (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish brown. No external differences in sex are seen until the turtle becomes an adult, the most obvious difference being the adult males have thicker tails and shorter plastrons than the females.
The Arrau turtle, 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) and the largest freshwater turtle in Latin America. 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 dams, the Arrau turtle is seriously threatened.
The Australian flatback sea turtle is a species of sea turtle in the family Cheloniidae. The species is endemic to the sandy beaches and shallow coastal waters of the Australian continental shelf. This turtle gets its common name from the fact that its shell has a flattened or lower dome than the other sea turtles. It can be olive green to grey with a cream underside. It averages from 76 to 96 cm in carapace length and can weigh from 70 to 90 kg. The hatchlings, when emerging from nests, are larger than other sea turtle hatchlings when they hatch.
The eastern long-necked turtle is an east Australian species of snake-necked turtle that inhabits a wide variety of water bodies and is an opportunistic feeder. It is a side-necked turtle (Pleurodira), meaning that it bends its head sideways into its shell rather than pulling it directly back.
Chelodina, collectively known as snake-necked turtles, is a large and diverse genus of long-necked chelid turtles with a complicated nomenclatural history. Although in the past, Macrochelodina and Macrodiremys have been considered separate genera and prior to that all the same, they are now considered subgenera of the Chelodina, further Macrochelodina and Macrodiremys are now known to apply to the same species, hence Chelydera is used for the northern snake-necked turtles.
The Florida softshell turtle is a species of turtle in the family Trionychidae. The species is native to the Southeastern United States.
The wood turtle is a species of turtle in the family Emydidae. The species is native to northeastern North America. The genus Glyptemys contains only one other species of turtle: the bog turtle. The wood turtle reaches a straight carapace length of 14 to 20 centimeters, its defining characteristic being the pyramidal shape of the scutes on its upper shell. Morphologically, it is similar to the bog turtle, spotted turtle, and Blanding's turtle. The wood turtle exists in a broad geographic range extending from Nova Scotia in the north to Minnesota in the west and Virginia in the south. In the past, it was forced south by encroaching glaciers: skeletal remains have been found as far south as Georgia.
The Roti Island snake-necked turtle, also commonly known as McCord's snakeneck turtle, is a critically endangered turtle species. It is named after Rote Island in Indonesia where it was first discovered. Some individuals were later discovered in East Timor, and are considered a distinct subspecies.
The Mary River turtle is an endangered species of short-necked turtle in the family Chelidae. The species is endemic to the Mary River in south-east Queensland, Australia. Although this turtle was known to inhabit the Mary River for nearly 30 years, it was not until 1994 that it was recognised as a new species. There has been a dramatic decrease in its population due to low reproduction rates and an increase of depredation on nests.
The Argentine snake-necked turtle, also known commonly as the South American snake-necked turtle is a species of turtle in the family Chelidae. The species is known for the long neck to which its common names refer. Despite appearances, the Argentine snake-necked turtle is probably more closely related to the mata mata than to the Australian snake-necked turtles in the genus Chelodina. H. tectifera is found in northern Argentina, Uruguay, Paraguay, and southern Brazil. Not much is known about it, as it has not been extensively researched. It is a popular pet in the exotic pet trade.
The New Guinea snake-necked turtle is a species of turtle in the family Chelidae. The species is found almost exclusively within Western Province, Papua New Guinea.
The northern snake-necked turtle or northern long-necked turtle is a species of turtle in the family Chelidae or Austro-South American Side-necked Turtles. It is native to northern Australia and southern New Guinea.
The Magdalena River turtle or Rio Magdalena river turtle is a species of turtle in the family Podocnemididae, which diverged from other turtles in the Cretaceous Period, 100 million years ago. It is endemic to northern Colombia, where its home range consists of the Sinú, San Jorge, Cauca, and Magdalena river basins.
The eastern river cooter is a subspecies of turtle native to the eastern United States, with a smaller population in the midwest. It is found in freshwater habitats such as rivers, lakes, and ponds.
The saw-shelled turtle is a species of turtle in the Chelidae family endemic to Australia, ranging along rivers and streams and connected swamps and lagoons from coastal Cape York Peninsula to northern New South Wales, with populations also noted as far south as Newcastle -. They are thought to have been introduced to Lake Eacham in the Atherton Tablelands. Other common English names are: serrated snapping turtle or common sawshell turtle.
Chelodina canni, also known commonly as Cann's snake-necked turtle, is a species of turtle in the family Chelidae. The species is endemic to Australia, where it is found in the northern and northeastern parts of the continent. It has a narrow zone of hybridization with its related species the eastern snake-necked turtle, C. longicollis. For many years C. canni was assumed to be the same species as C. novaeguineae from New Guinea. However, in 2002 it was shown that these two species differ both morphologically and genetically, and therefore C. canni was separated and described as a unique species.
Chelodina (Chelydera) burrungandjii, the sandstone snake-necked turtle or Arnhem Land long-necked turtle, is a medium-sized turtle reaching carapace lengths of 316 mm. The species is found in the sandstone plateaus and escarpments and the plunge pools of Arnhem Land of the Northern Territory. The species had been long recognised as valid. However, it had been difficult to research due to the remoteness of its habitat. Efforts to breed this species in captivity had been largely unsuccessful, until National Aquarium Herpetologist Matthew Benedict lead a successful breeding project in 2021. The species occurs in proximity to Chelodina rugosa, to which it is closely related. For the most part the two species are parapatric in distribution. However, they do come together in limited locations such as plunge pools at the base of the escarpments. In these areas there is hybridization between the species.
The southern river terrapin is a riverine turtle of the family Geoemydidae found in Malaysia, Indonesia and Cambodia.