Will this Bat return?

Did you know that what is possibly the world’s rarest bat lives only in Seychelles? The Sheath-tailed bat or Sousouri Banan is one of only two mammals occurring naturally in the granitic islands (the other is the Fruit bat or Sousouri). It is endemic – it cannot be found anywhere else in the world. There are only about 40-100 individuals left. It is believed that to have any chance of saving the species, a population of 500 bats is the viable number. The challenge for us all is how do we increase the bat population by as much as this?

Sheath-tailed bat © Sinclair Laing

The species was once common in Seychelles, but it has undergone a great decline during the mid to late 20th century. At present it is listed as Critically Endangered in the IUCN Red Data list of the Globally Threatened Species of the world. If urgent measures are not taken, this species could well vanish forever.

Very little was known about the bat’s ecological needs – its habitat, where it roosts, and what has caused the population decline. Several possible reasons for its decline have been put forward, including attacks by barn owls, disturbance of roost sites, habitat loss, and declines in its insect food resulting from pesticide use.    

The bat feeds on insects at night, using echolocation, which involves sonar: ‘bouncing’ sounds off objects at wavelengths inaudible to the human ear. By this means, bats avoid collisions with solid objects such as trees, and find insects to eat. Within a roost cave, the bats use lower frequency sounds, and these can be heard by the human ear.

Bats are often extremely good indicators of the quality of our environment. Their presence, or otherwise, says much about the health of habitats. Bat declines could reflect wider problems. Further research is urgently needed to understand more about this species, and develop an action plan to save it. Public awareness and education also have a part to play.

Recent work under a project initiated by Nature Seychelles and implemented with a group of universities in the UK and the Ministry of Environment and Natural Resources confirms that previous bat populations on Praslin and La Digue now appear to be absent. However, the team has also discovered two previously unknown roosts on Mahe. This study has been able to present evidence that the species requires mature tree stands for foraging.

The study reveals that habitat loss is not the only factor in the decline of the species, and in fact probably is not the main cause of the extinction of populations on the two islands. This leads to the question of pesticide use and its link with the bats’ prey - insects. The study also highlighted the importance of roosts and roost protection, as they represent not only shelter, but centres for social interactions, and an important foraging area. It is not simply the roost itself that needs to be protected, but also the habitat surrounding each roost.

Seychelles is synonymous with conservation success stories. The night flying Sheath-tailed Bat may not be a visible problem to many people, but losing this unique species would be catastrophic – an environmental tragedy. The partners in this project are doing all they can to prevent this from happening. Any hope of saving the bat will require widespread support and further work. We are doing our best to secure more international support and funding to continue this project.

Nature Seychelles, 3rd February 2006

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