26.
Seychelles Sheath-tailed Bat
(Coleura seychellensis)
CR
Overview
This bat belongs to an ancient family of sheath-tailed bats, so-called because of the nature of the membrane which stretches between the hind legs. By adjusting the hind legs in flight, this membrane can be lengthened or shortened as it slips over the tail, increasing manoeuvrability in flight. Previously common on the Seychelles Islands, this bat 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. Conservation programmes require support in order to ensure that this species has a future.
Urgent Conservation Actions
Protection of known and potential roost sites, habitat management, assessment of the impact of introduced predators, monitoring of known populations and public awareness programmes.
Distribution
Seychelles.
Media from ARKive
ARKive image - Seychelles sheath-tailed bat hanging from cave ceiling
ARKive image - Seychelles sheath-tailed bat
ARKive image - Seychelles sheath-tailed bat in flight
ARKive image - Seychelles sheath-tailed bats flying between caves
ARKive image - Seychelles sheath-tailed bats roosting
Evolutionary Distinctiveness
Order: Chiroptera
Family: Emballonuridae
The Emballonuridae (sheath-tailed bats) contains 13 modern genera and 51 species. They are also known from the Eocene/Oligocene (around 38 million years ago) and Pliocene (7 million years ago) of Europe, and the Miocene (26-7 million years ago) of Africa. The genus Coleura contains two species, C. afra (African sheath-tailed bats; mainland Africa and Madagascar) and C. seychellensis (Seychelles sheath-tailed bat).
Description
Size: 
Head and body length: 55-65 mm
Tail length: 12-20 mm
Forearm length: 45-56 mm
Weight: Male: 10.2 g
Female 11.1 g
This small bat is reddish brown or dark brown in colour with paler underparts. The name “sheath-tailed” refers to the membrane that stretches between the hind legs. By adjusting the hind legs in flight, this membrane can be lengthened or shortened as it slips over the tail, increasing manoeuvrability in flight.
Ecology
The species is nocturnal and feeds exclusively on insects. During the day the bats roost inside caves. When disturbed they often hang from the ceiling by all four limbs, with their stomachs pressed against the surface, although hanging by their feet is usual when they are relaxed. Females give birth to a single offspring during the rainy season (November-December) and sometimes in March-April.
Habitat
Found in coastal areas, where it roosts in boulder caves. Research on foraging and activity patterns indicate that individuals not only rely on coastal woodland for roost sites but also remain close to the coast for foraging and feeding habitats. Extensive searches for foraging habitat have failed to locate bats in upland areas and nearly all records of feeding activity are from coastal environments. They require a diverse, natural forest which supports abundant insects, especially moths and beetles.
Distribution
Endemic to the Seychelles Islands, this species is now known only from the island of Silhouette and the west coast of Mahé. Recent studies by the Government of Seychelles and Nature Seychelles failed to detect any bats at previously known roosting sites on the islands of La Digue and Praslin and the species is now thought to be extinct on both islands.
Population Estimate
Fewer than 100 bats are believed to survive, in just two locations. A 2003 study by the Nature Protection Trust of the Seychelles (NPTS) recorded 32 bats in a single cave system on the island of Silhouette. Studies conducted by Nature Seychelles in 2004 and 2006 have recorded a maximum of 55 bats in three roosts on the coast of Mahé. Throughout the course of monitoring the roosts on Mahé the number of bats recorded fluctuated, leading to speculation that roost emergences may be influenced by breeding patterns or movement between roosts. Monitoring of the Mahe roosts is carried out occasionally by the Seychelles Ministry of Environment. The main Silhouette population is monitored daily using a CCTV system. This population currently (December 2008) stands at 34 bats. A second population exists on Silhouette but may be reduced to a single bat. The maximum current population is therefore 90 individuals.
Population Trend
The population has undergone a severe decline over the last 30 years. However, intensive habitat management and roost protection has enabled the Silhouette population to recover and to start increasing.
Status
Classified as Critically Endangered (CR C2a(i)) on the 2010 IUCN Red List of Threatened Species.
Threats
This species has declined mainly due to habitat deterioration. It has been speculated that introduced Barn Owl (Tyto alba) may predate on the bats and as such may have influenced population numbers, but this is difficult to substantiate. There is no doubt that the species has declined due to loss of habitat to human development as a number of caves previously providing roost sites for this species have been lost to development. The roost on Silhouette has faced pressure from tourism development, leading to a decline in the number of bats. The only viable roosts on Mahé are adjacent to areas where hotel developments are underway or have been approved. This is likely to lead to roost abandonment and a very real risk of extinction fo the species on Mahe. The reliance of this species on coastal habitats places it under continued pressure from housing and tourism developments and their related infrastructure both on Mahé and Silhouette. Even in the absence of development pressures invasive plant species are causing the deterioration of feeding habitat, leading to a reduction in their favoured beetle prey and reduced breeding success.
Conservation Underway
Monitoring of the Mahé population has been led by Nature Seychelles and the Department of Environment. On Silhouette, the Nature Protection Trust of Seychelles (NPTS) has been active in research and conservation of the population since 1997.

In 2004 Nature Seychelles and a group of British university students secured funding from the British Petroleum (BP) Conservation Programme to conduct the “Bats on the Brink” assessment of roost locations and populations on Mahé. The survey located the remaining three roosts on Mahé and established that previous roosts on La Digue and Praslin are no longer active, failing to detect any bats on these two islands.

The NPTS has monitored the Silhouette population since 1997 and has developed a management plan for the island, which includes conducting research on the island ecosystems, habitat restoration, and the establishment of an island tropical research station. Implementation of this has resulted in the expansions of the main Silhouette roost from 24 individuals in 1997 to 32 in 2003 and 34 in 2008. Habitats around abandoned roosts are being actively restored. The plight of this species has been extensively publicised and all known roosts were located based on local information. Redevelopment of a hotel near the roost led to increased disturbance from smoke, vehicles, and rats and cats associated with waste disposal problems. As a result the population declined in 2004-5. Cessation of disturbance and intensive habitat management resulted in a good breeding season in 2007, with the population recovering to 32 bats. Continued habitat management allowed further increases to a new population maximum of 34 flying bats and 4 dependant babies by the end of 2008. Bats started visiting one of the abandoned roosts for the first time that year and it is hoped that they will start to reoccupy their former range in the near future. The Silhouette roost will be included in the Silhouette National Park which is expected to be designated soon.
Projects
Conservation Proposed
As this species roosts in boulder caves that sometimes occur in remote or difficult to access locations, it is hoped that some roost sites will be protected from further development or encroachment. While surveys continue on Mahé to identify potential roost sites more work is urgently required to enable their protection. Current identified roost sites on both Mahé and Silhouette require further legal protection to ensure they are not affected by development and ongoing long term monitoring for all roost sites is required. The Silhouette roosts should soon be protected by the Silhouette National Park which is being designated. Two of the three Mahe roosts are adjacent to development sites and serious disturbance to the bats is inevitable. The one relatively secure roost only contains 1-2 bats and is probably not viable. Survival of the species on Mahé requires urgent and effective legal protection, preventing development in the surrounding areas and intensive habitat restoration.

Detailed research into the biology, ecology and habitat requirements of the species is being undertaken on the Silhouette population; this will allow threats to be further identified and effective conservation measures implemented.

Detailed genetic studies on individual roost sites as well as across the entire species, including both Mahé and Silhouette populations are being undertaken to provide further information on the population size, sex ratios and overall species genetic structure and enable further decisions on the conservation and management of this species.
Associated EDGE Community members

Laura is a researcher who specialises in bat ecology and conservation

Justin is the Scientific Co-ordinator of Nature Protection Trust of Seychelles

A conservation officer working for the Seychelles government.

Links
Nature Protection Trust of Seychelles
This non-profit NGO aims to conserve the biodiversity of these unique islands. Conservation projects are based on informed scientific research which aims to protect species by protecting their habitats. A sheath-tailed bat project has been proposed and is waiting for funding for implementation.
References
Ball, N. 2004. A possible high-altitude roost of Seychelles sheath-tailed bats Coleura seychellensis. Phelsuma 12: 136-140.

Bambini, L., Blyth, A., Bradford, T., Burthe, S., Craig, L., Downs, N., Laing, S., Marshall-Ball, L. & McGowan, D. 2005. Bats on the Brink. Final Report, Unpublished report , University of Aberdeen, Aberdeen, UK.

Bambini, L., Blyth, A., Bradford, T., Bristol, R., Burthe, S., Craig, L., Downs, N., Laing, S., Marshall-Ball, L., McGowan, D., Racey, P. & Vel, T. 2006, Another Seychelles endemic close to extinction: the emballonurid bat Coleura seychellensis. Oryx, volume 40: 310-318.

Burgess, H. and Lee, N. 2004. A behavioural study of the Silhouette sheath-tailed bat (Coleura seychellensis). Phelsuma 12:69-77.

Gerlach, J., Mickleburgh, S., Hutson, A.M. & Bergmans, W. 2008. Coleura seychellensis. In: 2010 IUCN Red List of Threatened Species. Version 2010.4. Downloaded on 12 November 2010.

Gerlach, J. 2009. Pers Comm.

Gerlach, J. 2004. The bats of Silhouette Island, Seychelles. Phelsuma 12: 78-90.

Gerlach, J. 2008. Conservation of the Seychelles sheath-tailed bat Coleura seychellensis on Silhouette Island, Seychelles. Endangered Species Research.

Hutson, A. M., Mickleburgh, S. P. and Racey, P. A. (Compilers). 2001. Microchiropteran Bats: Global Status Survey and Conservation Action Plan. IUCN/SSC Chiroptera Specialist Group. IUCN: Gland, Switzerland.

Joubert, F. 2004. A preliminary investigation into the general ecology, status and habitat of the Seychelles sheath-tailed bat Coleura seychellensis (Emballonuridae).Phelsuma 12:54-68.

Nature Protection Trust of Seychelles. (Sep 2005).

Nature Seychelles’ Sheath-tailed bat page . (Apr 2007).

Nowak, R.M. 1999. Walkers Mammals of the World. Sixth edition. The Johns Hopkins University Press, Baltimore and London.

Rocamora, G. and Joubiert, F. 2004. The Seychelles sheath-tailed bat Coleura seychellensis: monitoring methodologies and recommended priority actions. Phelsuma 12: 48-53.

Distribution map based on data provided by the IUCN Global Mammal Assessment.

if you can provide new information to update this species account or to correct any errors, please email us at info@edgeofexistence.org


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