Ganges soft-shelled turtle (Nilssonia gangetica)
|Also known as:||Indian softshell turtle|
|Synonyms:||Aspideretes gangeticus, Trionyx gangeticus, Trionyx gangeticus mahanaddicus|
|Size||Adult length: up to 94 cm (2)|
Hatchling length: 43 – 47 cm (2)
Hatchling weight: 9 – 12 g (2)
Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix I of CITES (3).
With its prominent, tube-like snout and incredibly flattened shell, the Ganges soft-shelled turtle is a very peculiar-looking freshwater reptile. It is these odd features that make this turtle so superbly adapted to its riverine habitat, with its long neck and snorkel-like snout allowing it to extend its nose out of the water to breathe, and its compressed shell creating a stream-lined silhouette that makes it a brilliant and fast swimmer (4). The Ganges soft-shelled turtle has a round to oval, smooth upper shell (carapace), which is olive or green in colour with a yellow border. The limbs are also green, while the shell on the underside of the turtle’s body is grey to cream. It has a broad head, with several black stripes running from the centre towards the sides (2). Juvenile Ganges soft-shelled turtles can be identified by the dark eye-shaped markings and rows of round bumps that adorn the shell (2).
The Ganges soft-shelled turtle is found in the Ganges, Indus and Mahanadi river systems of Pakistan, northern India, Bangladesh and southern Nepal (2).
This turtle inhabits deep rivers, streams, large canals, lakes and ponds, with a bed of mud or sand. It tends to prefer areas where the water is turbid (2).
Despite its relatively small size, reported observations of the Ganges soft-shelled turtle paint a picture of a voracious and skilled predator. This turtle sometimes feeds in large groups, one of which has even been seen attacking, killing and feasting on a Nilgai antelope (Boselaphus tragocamelus) in a canal in India (5). However, an attack on such a large animal is probably a rare occurrence, and the omnivorous Ganges soft-shelled turtle spends more time eating aquatic plants and a large variety of smaller animals, such as fish, molluscs, insects, amphibians, and waterfowl (2). Animal carcasses, which are frequently dumped in the rivers it inhabits, are also fed upon, resulting in this turtle being called a ‘waterlogged vulture’ (5).
Mating activity in the Ganges soft-shelled turtle occurs in shallow waters during the monsoon season (September to February). Courtship is thought to begin with the male producing low, hoarse, cackling sounds to attract the female, and once an interested female has been found, the male swims around the female in decreasingly small circles before mounting. This courtship ritual lasts approximately four to five minutes. Whilst mounted, both the male and female float with their heads protruding from the water in order to breathe, as copulation can continue for up to 50 minutes (2).
Nesting occurs any time between May and January, although there is a peak in activity between December and January. The female burrows into a sandy river banks, digging a flask-shaped nest cavity into which is laid a clutch of between 8 and 47 eggs. Incubation lasts for between 251 and 310 days and the hatchlings emerge around July (2).
The main threat to the Ganges soft-shelled turtle is its trade in East Asia, which amounts to 30 to 40 tonnes a week (1). The Asian food trade is the primary contributor, as turtles are captured for their meat, but the shells are also sold as masks to tourists and some are kept as pets (6). Professional fishing has also become a problem, as river-dwelling turtles become trapped in the fishermen’s nets (7).
Nearly all freshwater turtle species in Asia are suffering as a result of habitat loss due to the closure of canals, introduction of dams, tidal barrages, channelization and flood plain drainage (5), partly the result of an expansion of agriculture. Pollution is also a significant problem in the rivers inhabited by turtles (5).
The Ganges soft-shelled turtle is known to occur in the Pench Tiger Reserve (8), and may occur in other protected areas throughout its large range. The Ganges soft-shelled turtle is also being bred in captivity in Sayaji Baug Zoo and other Gujarat zoos, India (9), which acts as insurance should the worst befall this species in the wild, and also gives scientists an opportunity to study the turtle and, hopefully, better understand its conservation needs. In addition, the Ganges soft-shelled turtle may benefit from efforts to conserve Asian turtles in general, such as a project initiated in Nepal in 1997 by the Amphibian and Reptile Conservation of Nepal (ARCO-Nepal), which monitors protected parks and other areas suitable for turtles, and creates educational material and training programs aimed at a wide spectrum of the population (6).
To learn more about the conservation of freshwater turtles see:
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- Amphibians: cold-blooded vertebrates (animals with a backbone) which typically hatch as aquatic larvae with gills. The larvae then transform into adults with air-breathing lungs. Includes frogs, toads and salamanders.
- Incubation: the act of incubating eggs, that is, keeping them warm so that development is possible.
- Molluscs: a diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
- Omnivorous: feeding on both plants and animals.
- Turbid: cloudy or muddy; not clear.
IUCN Red List (May, 2010)
- Ernst, C.H., Altenburg, R.G.M. and Barbour, R.W. (1997) Turtles of the World. ETI Information Systems Ltd, Netherlands.
CITES (May, 2010)
- Vitt, L.J. and Caldwell, J.P. (2009) Herpetology: An Introductory Biology of Amphibians and Reptiles. Third Edition. Academic Press, Burlington, Massachusetts.
- Moll, D. and Moll, E. (2004) The Ecology, Exploitation and Conservation of River Turtles. Oxford University Press, Oxford.
- Scleich, H. (2003) Turtle conservation by ARCO Nepal. Trionyx, 1(1): 13.
- Azam, M. and Randhawa, A. (2008) Studies on Wildlife Diversity of Two Wetlands with Particular Reference to Freshwater Turtles. Zoological Survey Department, Islamabad.
- Chandra, K. and Gajbe, P. (2005) An inventory of herpetofauna of Mahya Pradesh and Chattisgarh. Zoo’s Print Journal, 20(3): 1812-1819.
- Vyas, R. (2000) A review of reptile studies in Gujarat State. Zoo’s Print Journal, 15(12): 386-390.