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Seychelles sheath-tailed bat

By on March 16, 2007 in EDGE Updates, Uncategorized

Justin Gerlach

Dr Justin Gerlach is working with the Nature Protection Trust of Seychelles to conserve the Seychelles sheath-tailed bat (Coleura seychellensis), ranked 25th on the EDGE list. Previously common on the Seychelles Islands, this species has undergone a severe population decline over the past 30 years. Less than one hundred bats are believed to survive today, in just two locations.

I was born in Seychelles and growing up in a tropical environment stimulated my interested in nature and conservation.  From an early age I knew I wanted to be a biologist and studied Zoology at Oxford University, completing a doctorate there in 1994 on the ecology of carnivorous snails (I have always like the obscure).  My original interest in tropical snails has extended to cover all aspects of tropical island ecology, evolution and conservation.  I am particularly interested in how the evolution of the fauna and flora of islands influences their ecology and to what extent they are able to adapt to environmental change caused by human actions. 

In recent years my research interests have been focused on the investigation of the conservation needs of the Seychelles islands, providing the hard scientific data which I believe needs to underlie conservation planning.  A major part of this is the Indian Ocean Biodiversity Assessment which has assessed the taxonomy and conservation status of all the organisms of the 115 Seychelles islands.

My work on the Seychelles sheath-tailed bat has developed from the Silhouette Conservation Project of the Nature Protection Trust of Seychelles.  Silhouette is the third largest of the Seychelles group and although these islands are well known as a tourist destination several of the islands, such as Silhouette, remain in an almost untouched state.  With a land area of 1,995 hectares and a maximum altitude of 750m (Mont Dauban) the island has exceptionally high levels of biodiversity.  Due to its steep mountains the island has not been suitable for development and has therefore retained much of its natural flora and fauna.  The Silhouette Conservation Project aims to ensure the future for the unique species of the island (some 250 plant and 2000 animal species, 500 found only on Silhouette).  This includes the largest known population of Seychelles sheath-tailed bat.

Coleura seychellensis 

Since 1997 we have been monitoring the main roost of the species and slowly gathering information on its habits and conservation needs.  From a low of 16 bats at the start of the work we have seen the number of bats grow to a high of 32.  Although this is a tiny colony, it remains the largest known population of the species.  The world population is thought to be between 50-100 bats. 

In 2003 I started researching the species more intensively and with the assistance of volunteers and students have searched much of the island looking for roosts.  A number of abandoned roosts have been found and one further occupied roost was located.  Some work was carried out into behaviour in the main roost but this proved difficult as we could not afford to take any risks of disturbing such a threatened species.  In 1996 we installed a CCTV camera in the roost to enable monitoring and this has allowed us to make great strides forward in our understanding of the bats.

Although the Seychelles sheath-tailed bat is only one of the thousands of species restricted to the Seychelles islands and one of many threatened with extinction it is particularly significant for conservation in the islands.  It is one of only two bat species in the islands and for many decades has been a very enigmatic species, hard to find and harder to study.  Last year saw us make the first steps in understanding the species.  2007 marks 10-years since I saw my first Seychelles sheath-tailed bat and should see several exciting new developments in research on the species.  I hope that this year we can make similar advances in its conservation.

If you wish to find out more about Justin’s important work or support the conservation of this critically endangered species, please visit the Nature Protection Trust of Seychelles website or email Justin directly at