The Seychelles Sheath-tailed bat: Another endemic on the brink of extinction?-Actions abound but nature has its way


08-October-2012

The Sheath-tailed bat


The report listed the 100 most endangered species occurring in the world. These species are prone to extinction if immediate actions are not taken to address factors that have led to decline in their populations.

Unfortunately two species from Seychelles have been listed. The first one being the Seychelles Sheath-tailed bat  (Coleura seychellensis) or ‘Sousouri Bannan’ in Creole, an endemic bat which was historically found on Mahe, Praslin, La Digue and Silhouette. Historical data indicate that the species was abundant in the early 1960s on Mahe and 1970s on Silhouette. Its distributions have been reduced to Mahe and Silhouette in the recent years while survey during 2009 failed to locate any individuals on both Praslin and La Digue. It is believed the species went extinct in mid 1970 and 1980 respectively on these islands.

The species was listed in IUCN Red list since 1988 with an endangered status. However, gradual decrease in the population has been attributed to various factors of which many have not been proven and this has led the species to be categorised as critically endangered in 1996. This listing was based on criteria C2a (i, ii) of IUCN, which indicated that the population size and rate of decline are of great concern and likely to result in extinction unless actions are taken.
 
The IUCN is the world’s oldest and largest global environmental organisation and its central mission is to conserve biodiversity. The organisation founded an IUCN Red List of Threatened Species in 1963. This list is the world’s most comprehensive inventory of the global conservation status of species. The IUCN Red List is set upon precise criteria to evaluate the extinction risk of thousands of species and subspecies.

Species are classified by the IUCN Red List into groups that are set through criteria such as rate of decline, population size, area of geographic distribution, and degree of population and distribution fragmentation. The classification system is based on the following categories:

Extinct (EX) – species not definite located in the past 50 years.; Critically Endangered (CR) – Extremely high risk of extinction in the wild.; Endangered (EN) – High risk of extinction in the wild and whose survival is unlikely if the causal factors continue ; Vulnerable (VU) – likely to move into the ‘Endangered’ category in the near future if causal factors continue operating; Rare (R – Species with small populations that are not at present ‘Endangered’ or ‘Vulnerable’ but are at risk ; Least Concern (LC) – Lowest risk and does not qualify for a more at risk category.
Widespread and abundant taxa are included in this category ; Data Deficient (DD) – Not enough data to make an assessment of its risk of extinction.

The Ministry of Environment and Energy (MEE) started implementing monitoring programmes in early 1996 to assess status of the population by conducting intensive field work to locate roosting and foraging areas. This has since then led to annual monitoring with data being used as indicator of the species status and has assisted in determining population trends over the years.

During 2004, the MEE decided on a collaborative approach whereby technical expertise was sought from leading bat experts and this resulted in a partnership between the MEE, Aberdeen University and Nature Seychelles. This has resulted in the first Strategic Plan targeting the long-term conservation of the species.

Results from this partnership approach revealed a population size of only 19 individuals on Mahe.
 
During 2007-2008, the MEE, the Nature Protection Trust of Seychelles were involved in a joint project to manage the population on Silhouette and to identify conservation needs on Mahe.

Results obtained from this partnership have helped to draft an Action Plan. Nature Seychelles obtained funding to continue with research during 2009 and 2010 targeting to improve on the bat status but eventually fund became an issue which saw the end of monitoring on the species.

Since then, the MEE has been more or less the only body conducting regular monitoring. This includes contracting out more intense monitoring as well as conducting our own so as to have a more global overview of the population trend. This has shown that even if the actual number of individual remains low, it is stable and there has even been sign of an increase in population size.
On Silhouette Island a population of 40 bats have been counted in 2009 compared to just 27 in 2008 or from a low point of only 18 individuals; Anse Major has seen a significant increase from only 2 individuals in 2005 to 14 individuals in 2012; Cap Ternay and Baie Lazare populations are stable with 27-32 and eight individuals respectively.

MEE has also established collaboration between different ministries to secure and give legal protection to roosting and feeding sites on Mahe while the Silhouette population is safe from potential development through the network of collaboration that exists between the MEE, the Islands Development Company (IDC) and the Island Conservation Society (ICS). Furthermore there are financial contributions from private land owners into a special fund for the protection of Sheath-tailed bats.

Moreover the MEE has established strict conditions for development in the vicinity of known roosting and foraging areas through conditions that are designed specifically to ensure minimal disturbances or to prevent any modification of existing habitats. MEE has also been liaising with tourism establishments to curb on use of pesticides as invertebrate is the primary prey for the species.

The MEE commitments towards the long-term conservation of this species remains as strong as ever and we do call upon other partners to continue with efforts so as to assist in ensuring that this species survive.

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