Re-introduction and supplementation of terrapins on Silhouette Island, Seychelles

Summary

Two Critically Endangered Seychelles endemic terrapin subspecies, the black mud turtle and the yellow-bellied mud turtle, were the focus of a captive breeding and reintroduction program run by the Nature Protection Trust of Seychelles on Silhouette Island beginning in 1998, targeting the island's well-preserved wetlands at Grande Barbe and La Passe. Captive breeding succeeded well for the black mud turtle but only three yellow-bellied mud turtles hatched successfully from wild-caught founders. In March 2002, five radio-tagged adult black mud turtles were released at Grande Barbe, followed by 18 juveniles in 2003; six-month radio-tracking found highly variable movement behavior, and all five original adults were still present when tracking ended, though later trapping surveys located only two, with sporadic sightings continuing through 2008. In 2009 the project shifted focus to the yellow-bellied mud turtle, releasing six adults into La Passe marsh, which already held a relict population of just three adults and offered better observational monitoring, with at least five individuals subsequently seen. The project was unexpectedly forced to close in December 2010 when NPTS was evicted from Silhouette Island by the Islands Development Company, requiring an unplanned release of the ten remaining captive terrapins. Major difficulties included the black mud turtle's cryptic, crepuscular, marsh-dwelling habits that make it extremely hard to trap or observe, and short-lived radio tags limited by funding. The project rates itself Partially Successful, citing reasonable adult survival above 40% after eight years but acknowledging inadequate agency support prevented full success.