Three native species of terrapins (freshwater turtles or mud turtles) have been recorded from Seychelles. The Seychelles terrapin Pelusios seychellensis was an endemic species but latest research suggests it is probably extinct. The black mud turtle P. subniger parietalis. and the yellow-bellied mud turtle P. castanoides intergularis are endemic subspecies, genetically indistinguishable from similar mud turtles of Madagascar and east Africa. It has been suggested that they are actually introduced species and this remains a point of debate. Historically terrapins were recorded on Mahé, St. Anne, Cerf, Silhouette, Praslin, Cousin, Aride, Curieuse, La Digue and Fregate. It is probable that they also inhabited North and Cousine. Following drainage of lowland marshes and consumption by humans in the 19th and early 20th centuries they have become extinct on St. Anne, Silhouette and Aride. Ranges on all islands are significantly reduced, this is almost certain to mean that current population sizes are also reduced. In 2005 population estimates were 584-728 P. subniger and 76-158 P. castanoides. Their restricted ranges, low populations, recent declines in range (and probably populations)and serious threats to survival categorize both subspecies as Critically Endangered.
Studies of Seychelles terrapins were restricted to taxonomic accounts until the first distribution data were collected in 1983. This was followed by status and ecological studies carried out by the NPTS in June-September 1996. This project, short-listed by the Whitley Award for Animal Conservation, established protocols for a monitoring programme which the NPTS continued in January and July 1997.
The status study identified three main threats to the survival of both taxa: collapse of marsh ecosystems through water lettuce invasion, drainage and predation. Water lettuce invasion and drainage were regarded as the most significant threats. Predation by cats and dogs appears to be significant due to the large populations of domestic animals around most marshes on Mahé, Praslin and La Digue. It is not a significant factor on other islands. Pollution is also suspected to be a threat, but no data exist on pollution in terrapin sites. The American red-eared slider terrapin (Trachemys scripta elegans) was recorded from marshes on Mahé in 1996 and is generally believed to be implicated in terrapin population declines elsewhere in the world. Its potential effects on Seychelles terrapins are unknown at present.
Drainage continues to be a major threat; in 1999 the Anse Kerlan marsh on Praslin was drained to allow expansion of the airport on Praslin and the development of a golf course. This drainage has eliminated the main P. subniger parietalis population and current population estimates are reduced to 56-80 P. subniger parietalis and 1 P. castanoides intergularis, representing declines of over 45 and 99% respectively. There is an urgent need to raise the profile of marsh conservation in Seychelles before the last remaining fragments are lost.
There was no prior publicity for the drainage at Anse Kerlan. This lack of information to the Seychelles Governments Conservation Section or to NGOs meant that we lost a chance to rescue the terrapins from the site. Had this been possible we would have been able to start restoring populations in reserve sites. Instead the captive breeding project of the NPTS was crucial for the survival of both endemic subspecies.
The NPTS captive breeding project obtained its first eggs from P. subniger parietalis in January-March 1999, unfortunately all were laid in the water and did not hatch. The enclosures were improved later that year with financial support from the U.S. Ambassador's Self-Help Fund, improving breeding conditions but causing temporary disturbance. More eggs were laid in January 2000, again in the water. Of these 2 were rescued before they became waterlogged and these stated to develop. One of the eggs hatched on 3rd March. This is the first successful captive breeding of a Seychelles terrapin. The 2000/1 laying season resulted in more eggs laid in the water but these were rescued in time and 9 hatchlings produced. The first eggs P. castanoides intergularis were found, but unfortunately these were also laid in the water and not found in time. By 2005 three P. castanoides intergularis had been bred.
An experimental reintroduction of P. subniger was carried out on Silhouette and a Seychelles Terrapin Action Plan published in 2002. NPTS was involved with the reintroduction of terrapins to North Island. The first release occurred on North island in July 2008 and a breeding popualtion is now established there.
More details on these species can be found in the "Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group":
The first Seychelles terrapin captive hatchling