More Information

Additional Information

Amyda cartilagineaBlack-rayed Soft-shelled Turtle, Asiatic Softshell Turtle

By Jacob Vaught

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. (Asian Turtle Trade Working Group 2000, 2000; Ditmars, 1933; Fritz, et al., 2014)

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. (Ditmars, 1933; Gibbons and Greene, 2009; Jensen and Das, 2008a; Platt, et al., 2008)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range depth
    1 to 12 m
    3.28 to 39.37 ft

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. (Asian Turtle Trade Working Group 2000, 2000; Ernst, et al., 1992; Jackson, 2011; Nijman, et al., 2012)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    15 to 30 kg
    33.04 to 66.08 lb
  • Average mass
    20 kg
    44.05 lb
  • Range length
    70 to 83 cm
    27.56 to 32.68 in
  • Average length
    75 cm
    29.53 in

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. (Asian Turtle Trade Working Group 2000, 2000; Ernst, et al., 1992; Harless and Morlock, 1979; Jensen and Das, 2008a; Kuchling, 2009)

  • 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. (Alderton, 1988; Brinkman, et al., 2009; Carr, 1952; Ernst, et al., 1992; Harless and Morlock, 1979; Kuchling, 1999)

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. (Alderton, 1988; Ernst, et al., 1992; Harless and Morlock, 1979; Kuchling, 2009)

  • Breeding interval
    Asiatic soft-shelled turtles breed 3-4 times a year, the peak of breeding is in the middle of the summer.
  • Breeding season
    Females typically mate late April to early October.
  • Range number of offspring
    1 to 30
  • Range gestation period
    18 to 20 weeks
  • Average age at sexual or reproductive maturity (female)
    8-10 years
  • Average age at sexual or reproductive maturity (male)
    4-5 years

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. (Brinkman, et al., 2009; Harless and Morlock, 1979)

Lifespan/Longevity

We have no information on the lifespan of this species. Other species of soft-shelled turtles live for several decades. (Ernst, et al., 1992)

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. (Alderton, 1988; Carr, 1952; Ernst, et al., 1992; Jensen and Das, 2008a; Jensen and Das, 2008b; Lindeman, 2013)

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. (Harless and Morlock, 1979)

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. (Gibbons and Greene, 2009; Jensen and Das, 2008a; Kuchling, 1999)

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. (Asian Turtle Trade Working Group 2000, 2000; Ernst, et al., 1992; Jensen and Das, 2008b)

  • 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. (Jensen and Das, 2008c; Nijman, et al., 2012; Platt, et al., 2008; Shepherd R., 2000)

  • Anti-predator Adaptations
  • 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. (Ernst, et al., 1992; Jensen and Das, 2008c)

  • 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. (Asian Turtle Trade Working Group 2000, 2000; Jensen and Das, 2008a; Kuchling, 2009)

  • Positive Impacts
  • pet trade
  • 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. (Jensen and Das, 2008c)

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. (Asian Turtle Trade Working Group 2000, 2000; Jensen and Das, 2008c; Nijman, et al., 2012)

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. (Fritz, et al., 2014)

Contributors

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

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Alderton, D. 1988. Turtles & Tortoises of the World. New York, N.Y.: Facts on File.

Asian Turtle Trade Working Group 2000, 2000. "Amyda cartilaginea" (On-line). The IUCN Red List of Threatened Species. Accessed September 11, 2014 at http://www.iucnredlist.org/details/1181/0.

Bellairs, A. 1968. Reptiles. London, England: Hutchinson's University Library.

Brinkman, D., P. Holroyd, J. Gardner. 2009. Morphology and Evolution of Turtles. New York, & London: Springer Dordrecht Heidelberg.

Carr, A. 1952. Handbook of Turtles. Cornell University Press, Ithaca, New York: Comstock Publishing Associates.

Conant, R. 1998. A Field Guide to Reptiles & Amphibians: Eastern and Central North America. Boston: Houghton Mifflin.

Ditmars, R. 1933. Reptiles of the World; The Crocodilians, Lizards, Snakes, Turtles and Tortoises of the Eastern and Western Hemispheres. New York: The Macmillan company.

Ernst, C., R. Altenburg, R. Barbour. 1992. Turtles of The World. Washington, DC: Smithsonian Institution Scholarly Press.

Fritz, U., R. Gemel, C. Kehlmaier, M. Vamberger, P. Praschag. 2014. Phylogeography of the Asian softshell turtle Amyda cartilaginea (BODDAERT, 1770): evidence for a species complex. Vertebrate Zoology, 64/2: 229-243. Accessed December 06, 2015 at http://www.senckenberg.de/files/content/forschung/publikationen/vertebratezoology/vz64-2/09_vertebrate_zoology_64-2_fritz_229-243.pdf.

Gibbons, W., J. Greene. 2009. Turtles : The Animal Answer Guide. Baltimore: Johns Hopkins University Press: Johns Hopkins University.

Harless, M., H. Morlock. 1979. Turtles: Perspectives and Research. New York: Krieger Pub Co.

Jackson, D. 2011. Life in a Shell: Physiologist's View of a Turtle. Cambridge, Massachusetts: Harvard University Press.

Jensen, K., I. Das. 2008. Cultural exploitation of freshwater turtles in Sarawak, Malaysia. Chelonian Conservation and Biology, 7/2: 281-285.

Jensen, K., I. Das. 2008. Dietary observations on the asian softshell turtle from Sarawak, Malaysia. Chelonian Conservation and Biology, 7/1: 136-141.

Jensen, K., I. Das. 2008. Observations on the influence of seasonality, lunar cycles, and weather condition on freshwater turtle activity in Sarawak, East Malaysia. Asiatic Herpetological Research, 11: 37-42.

Kuchling, G. 1999. The Reproductive Biology of the Chelonia. New York, N.Y.: Springer-Verlag.

Kuchling, G. 2009. Endoscopic sexing of juvenile soft-shell turtles, Amyda cartilaginea. The Natural History Journal of Chulalongkorn University, 9/1: 91-93.

Lindeman, P. 2013. The Map Turtle and Sawback Atlas: Ecology, Evolution, Distribution, and Conservation. Norman, Oklahoma: University of Oklahoma Press.

Nijman, V., C. Shepard, M. Sanders, K. Sanders. 2012. Over-exploitation and illegal trade of reptiles in Indonesia. Herpatological Journal, 22: 83-89.

Platt, S., H. Sovannara, L. Kheng, R. Holloway, B. Stuart, T. Rainwater. 2008. Biodiversity, exploitation, and conservation of turtles in the Tonle Sap Biosphere Reserve, Cambodia, with notes on reproductive ecology of Malayemys subtrijuga. Chelonian Conservation & Biology, 7/2: 195-204.

Shepherd R., C. 2000. Export of live freshwater turtles and tortoises from North Sumatra and Riau, Indonesia: A Case Study. Chelonian Research Monographs, 2: 112-119.

Search

Navigation Links

Information
Classification

Classification