Seychelles biodiversity

Although the Seychelles sheath-tailed bat was described as common on Mahé island in the 1800s it is now extremely rare. It seems to have declined throughout the 1900s as habitats changed in the Seychelles islands. The 20th century saw a dramatic loss of lowland forests, cleared for coconut plantations, increased development and habitat change caused by invasive plants. In the 1980s it disappeared from Praslin and La Digue islands and now survives only on Mahé and Silhouette islands. On the latter it occupies two caves have been located.  These caves are part of a single system of passages in a boulder field. Three small roosts on Mahé have been located.

The Silhouette roosts were monitored by the Nature Protection Trust of Seychelles from 1997 until 2010. NPTS also initiated conservation work on the species and during that time managed to increase the Silhouette population from 18 bats to a maximum of 40. These low figures are an indication of the precarious status of this bat.

The successes on Silhouette resulted from habitat restoration around the roosts and the feeding areas. These stopped the roosts being over-run by invasive plants, and abandoned roosts were restored. By 2010 these old roosts had not been reoccupied but were being visited by bats occasionally. The management of the feeding areas resulted in increases in beetle populations (favored by the bats during the breeding season) and consequently a highly successful breeding season in 2007-8. After 3 years of decline the population recovered to the maximum of 32 by April 2008. 2008 proved to be a good year for the bats, with a new record of 37 bats set in December. At this time at least one bat was occasionally returning to an abandoned roost, and it seemed that the Silhouette population was finally starting to recover. Further progress was recorded in 2009 when numbers increased to 40. In early 2010 12 of the bats dispersed to start a new colony. Conservation work on the Silhouette population was forced to come to a halt in 2010 for political reasons.

On Mahé island an estimated 30-50 bats survive in three isolated roosts, all threatened by development and habitat deterioration. In 2009 NPTS worked with the Seychelles Ministry of Environment to propose conservation of the Mahé populations of sheath-tailed bats.

Population changes on the four islands

Praslin	La Digue	Mahé	Silhouette

Publications conservation of the Seychelles sheath-tailed bat:

• Rocamora, G. & F. Joubert 2004. Coleura seychellensis: monitoring. Phelsuma 12
• Gerlach, J. 2004. The bats of Silhouette island, Seychelles. Phelsuma 12
• Gerlach J & Taylor, M. 2006 Habitat as a critical factor in the decline of the Seychelles Sheath-Tailed Bat Coleura seychellensis. Acta Chiopt.. 8; 129-139.
• Gerlach, J. 2008. Status and conservation of the Seychelles sheath-tailed bat Coleura seychellensis on Silhouette island, Seychelles. Endangered Species Research.
• Gerlach, J. 2010. 2010 report on conservation of the Seychelles sheath-tailed bat.
• Gerlach, J. 2011. Conservation of the Seychelles sheath-tailed bat Coleura seychellensis. Phelsuma 19: 54-68