Amyda cartilaginea

Geographic Range

The Asiatic soft-shelled turtle, Amyda cartilaginea , is primarily found in southeastern Asia, in the lowlands of the peninsula and on the islands of Sumatra, Java, Lombok, and Borneo. It is present in all the nations of southeast Asia except the Philippines.

Fritz et al. (2014) propose that the species is actually a species complex, based on their genetic analysis. They also give a record for the species occurrence in Bangladesh.

• Biogeographic Regions
• oriental oriental
  • native native

Habitat

Similar to almost all soft-shelled turtles in the family Trionychidae , Asiatic soft-shelled turtles are freshwater species. Asiatic soft-shelled turtle is found in depths from 1 meter (near the shore) to 12 meters (e.g., approaching waterfalls). Hunters and fisherman within the Malaysian area have trapped these turtles in lakes, slow-moving rivers, and fast-flowing rivers that end in waterfalls.

• Habitat Regions
• tropical tropical

• Terrestrial Biomes
• forest forest
• rainforest rainforest

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• swamp swamp

• Other Habitat Features
• riparian riparian

Physical Description

The average adult carapace length is 70-80 cm, and Ernst et al. (1992) report maximum sizes up to 83 cm. This species also exhibits sexual dichromatism and dimorphism. The dichromatism is visible in the color of its plastron. Females have a gray plastron, while males typically are white. The tails differ by size and length, as well. Females have shorter tails, while males exhibit thick, long tails. Finally, males (20-25 kg) tend to be larger than females (15-20 kg).

As a juvenile and adolescent turtle, the carapace is complexly patterned, but the older turtle shells become quite drab. The juvenile’s once-greenish brown carapace with yellow and black spots becomes solely olive-colored. The rough adolescent carapace smooths out as the turtle ages. Asiatic soft-shelled turtles have many distinguishable traits from other soft-shells. These include an extremely long snout, and several permanent tubercles on its neck.

The snout of the turtle is elongated for breathing above the silt in which it buries itself. The evolutionary loss of the prenureal and dermal bones along the neck and spine of the turtle allow for greater flexibility in the neck and spine.

Soft-shelled turtles have special adaptations for "pharyngeal breathing." Structures lining the pharynx allow increased gas exchange from water pumped in and out of the pharynx, allowing for greatly increased submergence time.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful

Development

Asiatic soft-shelled turtles exhibit temperature-dependent sex determination. Temperature affects the beginning of sperm development and the female ovulatory cycle (only allowing these to occur when the climate is warm enough), and the sex of the offspring. Males are generally born when incubating in a nest around 25 degrees Celsius, while females are typically born around the 30 degree Celsius mark. The average egg diameter at hatching is 21-33 mm.

The development of traits from an adolescent soft-shell to an adult is mainly with its coloration. The base shape and structure of the head, carapace, and limbs are all the same for adults and younger turtles. Adolescent turtles between 3-5 years old have large tubercles on their carapace and very vibrant yellow spots on their head and neck. Large adult turtles around 8-10 years old lose the tubercles to a smooth carapace, and the yellow spots fade into lines on the adult’s green head. The growth of the turtles slows as it gets older and then is determinate to stop once the turtles reach full maturity.

• Development - Life Cycle
• temperature sex determination

Reproduction

The reproduction of Asiatic soft-shelled turtles takes place between late spring and early winter. The reproduction is heavily influenced by temperature, so the mating is primarily occurring in the peak of the spring around May. The actual mechanism to mating is assumed to be influenced through tactile behavior and male aggression. The tactile aspect involves typical soft-shell courtship with touching of the female head and carapace with the elongated claws of the male. There is also aggressive courtship by males if tactile courtship fails.

Whether the courtship is of tactile manner or aggression, males mount females to begin copulation. This copulation takes place underwater on the bottom. The support of the water helps the male maintain copulation. There seems to be no bond between mating partners. The turtles exhibit promiscuous behavior. The length of copulation, depth necessary in water, and whether or not this can occur terrestrially are not recorded.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Upon copulation, Asiatic soft-shelled turtles build nests to incubate their eggs. These nests are usually within 90 meters of the body of water where copulation occurred. Nests are dug into soft sand, similar to where they burrow. The building of a nest is said to be completely solitary, and without the aid of the male turtle.

These turtles typically reach sexual maturity as females between 8-10 years old, while males reach sexual maturity between 4-5 years old.

On average, they can lay 3-4 clutches in a year and consequently can build up to three or four nests in one season. These clutches have been recorded with a minimum of 1 offspring and a maximum clutch size of 30. Smaller, more adolescent females (4-5 years old) lay fewer eggs than larger, older females (8-10 years old). Incubation of the spherical eggs is between 126-140 days. This is very long in comparison to the incubation times of other soft-shelled turtles such as the smooth soft-shelled turtle, Apalone mutica , who has an incubation period of 56-84 days.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Asiatic soft-shelled turtles show some parental investment prior to the laying of their eggs. The females build a protective nest that incubates their young, and rotate the eggs within the nest. Once the turtle has built a safe hatching environment for her offspring, the mother leaves the hatchlings. Similar to feeding, the building of the nest takes place nocturnally.

• Parental Investment
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

We have no information on the lifespan of this species. Other species of soft-shelled turtles live for several decades.

Behavior

Asiatic soft-shelled turtles are facultatively aquatic turtles. They have adaptations for fast-swimming and for hiding in sediment. With the loss of the prenureal bone and dermal bones, which run along the vertebrae in the front of the carapace, it’s easy for the turtle to bury itself in the silty sediment. The turtle will dive head first into the substrate and use its limbs to kick up sediment. The sediment falls back down onto the turtle covering it almost completely, except for its snout.

While they spend the great majority of their time in the water they do occasionally emerge onto land at night. Tracking and capturing this species is quite difficult because they bury in mud and are underwater. As Jenson and Das (2008) observed, when searching for these turtles you would almost step on them before finding their nostrils protruding from mud.

These turtles are known to be aggressive in defending themselves.

Asiatic soft-shelled turtles exhibit clear seasonal patterns of activity. In the dry season, they are likely to burrow into patches of soft mud and aestivate, while activity and movement increased exponentially during the wet season.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• aestivation
• solitary solitary

Home Range

Not much seems to be known about the territorial behavior of the Asiatic soft-shelled turtle, but as confirmed by Harless and Morlock (1979), soft-shelled turtles rarely move outside their own areas of comfort.

Communication and Perception

Not much is known about the communication methods of the turtle. However, there are several morphological features that give clues to the way this animal communicates.

The Asiatic soft-shelled turtle has a highly evolved snout that it uses for hunting, sensing predators, and breathing while buried in mud.

With the development of elongated claws, which is typical of soft-shelled turtles, tactile communication is assumed to be the primary method of communication to initiate copulation with females. Kuchling (1999) observed, with males being larger, it is simplest for the turtles to use their elongated claws to make contact with the female’s heads.

• Communication Channels
• tactile tactile
• chemical chemical

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• vibrations vibrations

Food Habits

The Asiatic soft-shelled turtle is known for its carnivorous diet and nocturnal hunting patterns. It occasionally feeds on plant material, but animals are its primary food. Its diet consists of fish, amphibians, insects, and some crustaceans. The turtles are predators that ambush their prey. With its ability to breath in a gill-like fashion through pharyngeal breathing, it can stay submerged for hours in silt, snatching small fish or amphibians. The turtle’s long snout is used for sensing its prey.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • insectivore insectivore

• Animal Foods
• amphibians
• fish
• eggs
• insects
• aquatic or marine worms
• aquatic crustaceans

• Plant Foods
• leaves
• seeds, grains, and nuts
• fruit
• algae

Predation

The Asiatic soft-shelled turtle is very agile. Their thin carapaces and long necks allow for rapid swimming and diving away from predators and their ability to burrow also benefits them in hiding. We have little information on the predators of this species. Humans are probably the main predator of adults, but eggs and juveniles are probably taken by many predators. The coloration of the dorsal surface of this species provides camouflage while it rests on the bottom.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Asiatic soft-shelled turtles influence the environment through their roles as predators, prey, and sometimes scavengers. The turtle’s diet is typically carnivorous, but within the turtles fecal matter algae and berries have been found.

The soft-shelled turtles may limit the growth of populations of its prey, which includes fish, amphibians, insects, and some crustaceans.The turtles and its eggs also provide food for other predators.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Asiatic soft-shelled turtles are consumed as food and used as pets on a smaller scale.

Turtle oils from the carapace of most species have been used worldwide for treating minor ailments, and dermatological purposes related to preventing aging of the skin. Though these market benefits pale in comparison to the market for consumption, they still exist as a small positive market stimulation.

• Positive Impacts
• pet trade pet trade
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

These turtles can deliver a damaging bite when defending themselves, but otherwise there are no known adverse effects of Amyda cartilaginea on humans.

Conservation Status

The Asiatic soft-shelled turtle is currently listed as “Vulnerable” under the IUCN Red List. One of the main reasons for the declining population seems to be commercial harvest for sale as food.

In Malaysia, the Wildlife Protection Ordinance of 1998 protects most Malaysian turtles against exploitation. This has not prevented harvesting. The turtles are sought after for their size and taste by the people of Borneo and the greater Asian market.

The Asiatic soft-shelled turtle is listed under Appendix II of CITES, which requires that international exporters have a permit from their national government.

Other Comments

Fritz et alia (2014) report genetic analysis and propose that this species is actually a complex of several species, and these reflect ancient watershed patterns that existed prior to current sea levels.

Additional Links

Encyclopedia of Life

Contributors

Jacob Vaught (author), Radford University, Karen Powers (editor), Radford University.

References

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