Most Endangered Bat on Seychelles
Endemic Sheath-tailed Bat Population is Close to Extinction
Habitat loss and pesticides are among threats to one of ten most critically endangered species. Invasive, alien plant species also play a role in Seychelles bat decline.
The Seychelles, a group of islands 1000 miles off the east coast of Africa, are home to the Seychelles Sheath-tailed bat which holds the dubious distinction of being the most endangered and least understood of all the endemic species found on those islands. Non-native species may be partially to blame.
Seychelles Endemic Species
Islands often harbor endemic species. These distinct species evolve over time because of the isolation of island life. The Seychelle Islands are no exception, with over 75 endemic plants, 12 bird species, and 11 amphibians. Also, as is true for many islands, there are few mammals.
But there are two species of bat. The Seychelles flying fox (Pteropus seychellensis) is a fruit-eating bat that has recently been moved from the IUCN Vulnerable list to Least Concern status as its population has stabilized. The Seychelles Sheath-tailed bat (Coleura seychellensis) is not so lucky. This Critically Endangered species has a population of somewhere between 30 and 100 animals total, putting it among the ten most endangered mammals in the world.
Threats to Seychelles Sheath-tailed Bats
Unlike its fruit eating relative, the sheath-tailed bat is an insectivore, which makes pesticide use one of the suspects in its decline. But a recently discovered colony of Sheath-tailed bats feeds on very different insects which are not being controlled by pesticides. This has caused some biologists to dismiss them as a factor in the decline of the species. Another suspect is the barn owl (Tyto alba) which was brought to the islands in 1949 and preys on the bats.
Seychelle sheath-tailed bats roost in field caves near palm woodlands or marshes. Another introduced species, the highly invasive kudzu vine (Pueraria phaesolides), is growing so prolifically it is blocking the entrance to some of the traditional sheath-tailed bat roosting caves. Some of the vines around both active and abandoned roosts have been cut back and attempts are being made to remove the kudzu permanently.
Silhouette Conservation Project and Sheath-tailed Bats
The Nature Protection Trust of Seychelles (NPTS) with Dr Justin Gerlach, a native of the islands, heading up the work, is conducting studies of the bat to better understand habitat, social and foraging needs. They are focusing on the population of sheath-tailed bats found on Silhouette Island. This island has remained largely untouched thanks to its steep mountains, which make it difficult to develop.
As part of the Silhouette Conservation Project, Dr Gerlach and staff have been monitoring the largest colony of bats, which has grown from a low of 16 animals to the present 32, since 1997. As little is known for sure about the species, NPTS is concentrating its conservation work on protecting the existing habitat. One piece of information gleaned from the study is that the Seychelle sheath-tailed bats prefer mature tree stands for foraging. Protecting those stands will also aid other endemic species.
For each animal there is a tipping point beyond which the species cannot recover. It isn’t clear yet, and won’t be for some time, whether the Seychelles sheath-tailed bat can be brought back from the brink of extinction. It can only be hoped that for this rare bat the effort won’t be in vain.
