Flat-shelled spider tortoise  (Pyxis planicauda)

The various common names for this small tortoise generally refer to the noticeably flattened nature of either its oblong upper shell (carapace) or its tail (2) (4). The carapace is distinctively patterned, with each scute having a light brown to yellow centre surrounded by a wide, dark brown to black border. In older tortoises, an additional yellow border may surround this dark border (4). Yellow rays extend outward from the centre of the scutes, across the dark border. The scutes around the perimeter of the shell (marginals) are dark with a yellow band (2) (4). The lower shell (plastron) is yellow with scattered dark spots or rays along the sides (2) (4). The limbs range from yellow to brown in colour, and large yellow scales cover the hind legs (2). By contrast, the head ranges from dark brown to black, with some variable yellow markings (2) (4).

Endemic to the west coast of Madagascar (5), between the Monrondava and Tsiribihina Rivers (4).

Confined to lowland fragments of dry, deciduous forest, found only on the west coast of Madagascar (5).

The flat-shelled spider tortoise is active only during the hot/rainy season, from November until April/May, and is most active during and after rains (4) (5). During the cool/dry season, this species buries itself and lies dormant in the leaf litter of the forest floor (a period known as aestivation) (4). Breeding occurs during the hot/rainy season, and is followed a month later by egg-laying (5). Females may produce up to three clutches a year (5), each containing only one, relatively large egg (4). Hatching is timed with the return of the rainy season the following November (5).

The diet consists of fallen fruits from trees, and the shoots and leaves of bushes (4).

Like Madagascar's other tortoises, the flat-shelled spider tortoise has been severely threatened by harvesting for the international pet trade and rampant degradation of its habitat (2). Deforestation has been widespread due to conversion to agriculture, firewood collection and road construction for oil exploration (2) (5). The species' already precarious position has been compounded by excessive harvesting to sell to private collectors and zoos, which has resulted in its total elimination from some forest fragments. This species has also been sold in Chinese marketplaces for food. Even since their listing on CITES Appendix I, with export of wild specimens therefore banned, there have still been reports of tortoises being smuggled out illegally. In addition, there are serious concerns that specimens advertised as ‘captive-bred' are really captured from the wild. Given that the species has a low reproductive rate, and it is mostly breeding females that are collected, the flat-shelled spider tortoise has little capacity to recover from depleted numbers. Although predation is not thought to be a significant threat, the growing number of introduced predators, such as cats and dogs, on the island could increase mortality during egg-laying and hatching, and even in adults. Floods caused by cyclones are one of the natural threats which this species has to endure (2).

The flat-shelled spider tortoise has proven difficult to breed in captivity (2), although some zoos have been successful, most notably in the U.S. (5). Thus, creating an effective and sustainable captive-breeding programme to supply demand or to fuel reintroduction efforts would seem to be difficult. There are a few protected areas of forest within this species' range, such as the special Andranomena Forest Reserve and private Analabe Reserve, but regulations are apparently rarely enforced. Furthermore, most of the latter has been degraded and includes plantations and roads built for oil exploration (2). Thankfully, the flat-shelled spider tortoise was raised from Appendix II to Appendix I of CITES in 2003, banning all international trade in wild-caught specimens (3). Although illegal trade is still suspected to continue (2), which must be addressed, this legislation is likely to have quelled harvesting to some degree.

For further information on the flat-shelled spider tortoise see:

• CITES: Consideration of Proposals for Amendment of Appendices I and II, Prop. 12.55.:
  http://www.cites.org/eng/cop/12/prop/
• Turtles of the World (CD-ROM), by Ernst, C.H., Altenburg, R.G.M. and Barbour, R.W.:
  http://ip30.eti.uva.nl/BIS/turtles.php?menuentry=soorten&id=356

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