The Seychelles islands support three native taxa of freshwater turtle, two are endemic subspecies of African species (Pelusios subniger parietalis and P. castanoides intergularis) and the third a full endemic species (P. seychellensis). Both P. s. parietalis and P. c. intergularis are well-known and well-defined taxa, but P. seychellensis is very poorly known (being recognised from only three museum specimens collected in 1894). P. seychellensis appears to intergrade with P. c. intergularis, and continued taxonomic research may now suggest that the two form a hybrid complex, with P. seychellensis being extinct in a pure form.
Of the two definitely extant subspecies, P. s. parietalis inhabits marshes, either shallow muddy woodland pools or open reed beds. P. c. intergularis is typically riverine, although it occurs in some of the deeper reed beds in very low numbers. Both marshes and rivers in the Seychelles have been extensively disturbed by development, pollution, and alien water plant invasion (water hyacinth and water lettuce). It has long been believed that the terrapin populations are in decline (Bour, 1984).
The first population estimates were made in 1996 when all of the main terrapin sites were surveyed (Gerlach & Canning, 1996). Monitoring over the next three years further refined these estimates. By early 1999 the populations were estimated to be 400-450 adult P. s. parietalis and 200 P. c. intergularis. The endemic species P. seychellensis was suspected to be either extinct or an invalid species. In 1997 The Nature Protection Trust of Seychelles started its Seychelles Terrapin Conservation Project. The goals of this group were to raise awareness of the terrapins’ threatened status and the need for wetland conservation, and to reintroduce terrapins to secure sites (such as Aride, North, and Silhouette islands). Towards this latter goal, the NPTS established a captive breeding programme using rescued “pets” and terrapins removed from development sites. These terrapins were obtained with the support of the Seychelles Government’s Division of Environment.
By early 1999 the main populations of P. s. parietalis had been restricted to the reed beds at Anse Forbans on Mahé and Anse Kerlan on Praslin. P. castanoides was mainly restricted to the Rivière Mare Anglaise on Mahé with a small population on Praslin (also at Anse Kerlan). Significant populations may remain on La Digue, but are in continuing decline due to ecological problems in the marsh.
In 1999 the Anse Kerlan marsh was drained to allow expansion of the airport on Praslin and the development of a golf course. This drainage has eliminated the main P. s. parietalis population, reducing the estimated remaining population to 180–190 P. s. parietalis and 150 P. c. intergularis, which represents declines of 57 and 21% respectively. These major declines are due entirely to habitat destruction. Unfortunately, the importance of marshes is not widely appreciated in Seychelles. This is exemplified by the favourable Environmental Impact Assessment given for the Anse Kerlan drainage project prepared by the director of BirdLife Seychelles. There is an urgent need to raise the profile of marsh conservation in Seychelles before the last remaining fragments are lost.
Because there was no prior publicity about the drainage at Anse Kerlan, the Seychelles Government’s Conservation Section and NGOs were unaware of the project, and we lost a chance to rescue the terrapins from the site. Had we access to this information, we could have begun restoration of populations in reserve sites. Consequently, the captive-breeding project of the Nature Protection Trust of Seychelles has now become crucial for the survival of both endemic subspecies.
The captive-breeding project obtained its first eggs from P. s. parietalis in January–March 1999; unfortunately, all were laid in the water and did not hatch. Later that year, with financial support from the U.S. Ambassador’s Self-Help Fund, the enclosures were improved to enhance breeding conditions. More eggs were laid in January 2000, again in the water. Of these, two were rescued before they became waterlogged. One of the eggs hatched on 3 March. This is the first successful captive breeding of a Seychelles terrapin. It is hoped that the cause of the eggs being deposited in the water can be identified before the next laying season and that P. c. intergularisv can also be persuaded to breed.
Bour, R. 1984. Taxonomy, history and geography of Seychelles land tortoises and fresh-water turtles. In Stoddard, D.R. (Ed.) The Biogeography and Ecology of the Seychelles Islands. W. Junk, The Hague. Pp 281-307.
Gerlach, J. & Canning, K.L. 1996. Seychelles Terrapin Conservation Project. NPTS, unpublished.