Oxford Univerity Silhouette expedition

Justin Gerlach

The aim of this expedition was to characterise the Pisonia sechellarum forest on Silhouette Island, Seychelles. The island has important populations of rare animals, especially the Sechelles sheath-tailed bat (Coleura seychellensis silhouettae), endemic Amphibia and Lepidoptera. Silhouette is of great ecological importance and there are several plant species restricted to the island. There are also a large number of endemic invertebrates recorded for the island, several of which are extremely rare and many of these species were rediscovered by the expedition. It is stated that the number of known invertebrate species will undoubtedly increase with further research. Of the vertebrates, amphibians are particularly common and several species are restricted to Silhouette and Mahe. Silhouette has a large breeding population of white-tailed tropicbird and may be an important breeding ground for this species in the Seychelles. The Pisonia forest is an example of one of several localised, unique habitats on Silhouette. Due to its physical structure and restricted area it has very definite conservation requirements. The forest is located within the confines of the proposed mountain forest reserve. Legal protection is an important component in the preservation of all habitats and this is especially true of fragile areas such as the Pisonia forest. The forest is very sensitive and fragile in places, and the expedition minismised impact by using a single path avoiding the most sensitive areas. It is recommended that the forest is not visited by anyone except for scientific purposes, which should be widely separated temporally if possible, ensuring that the fragility of the area is respected. The forest suffers from Clidemia, which should be eradicated using extreme care, though some damage will be unavoidable. Other exotics do not pose a threat at present. If the area above the Pisonia forest erodes, there will be damage through excessive soil deposition and rock fall. Such erosion resulting from Clidemia control must also be prevented, this is possible if carried out with care.