The plants and animals of the Mentawai Islands have been evolving in isolation since the Mentawais split away from the big Indonesian island of Sumatra 500,000 years ago. The unique native mammals attract extensive scientific attention. But little of that research has been aimed at bats, and now the forests are disappearing so fast that the islands could lose entire bat species before we even learn they existed – much less try to save them.
Only nine species of bats have been formally reported on the Mentawai Islands, so I was incredulous when my own research quickly found 16 species – one of them previously undescribed.
I came to the islands to assist primatologist Lisa Patculli in her behavioral study of the endangered pig-tailed langur (Simis concolor), but I also had the opportunity to survey the region’s bat species. My goal was to increase public awareness of the values of bats and the impact they have on these islands.
Located off Sumatra’s west coast, the islands of Siberut, Sipora, North Pagai and South Pagai are known as the Mentawai Islands. My research site was on North Pagai, in an area called Betumonga. When I arrived, the site comprised 335 acres (135 hectares) of forest, some of it surrounded by villagers’ gardens. Fully half of that lush forest was illegally logged over the next few months.
I wondered if this devastated habitat had driven the bats away or concentrated them in the remaining patches of vegetation. The latter proved to be the case: My survey began even before I had erected my mist nets. I quickly discovered a sheath-tailed bat (Emballonura monticola) roosting under my desk, then located an entire roost of sheath-tailed bats with pups in a rocky shelter beside a small stream.
As I began setting mist nets at the study site, the research house and the edge of the forest, I captured and released a number of short-nosed fruit bats of the genus Cynopterus. I also caught a Hill long-tongued fruit bat (Macroglossus sobrinus) and a fruit bat known as Leschenault’s rousette (Rousettus leschenaulti), the first of its kind recorded on the islands. My nets also revealed several insect-eating bats, including a large leaf-nosed bat of the genus Hipposideros, which is probably an undescribed species, and three species of horseshoe bats (genus Rhinolophus) – the first recording of any horseshoe bat on Mentawai.
I was joined by an Indonesian graduate student, Mai, from Andalas University in the fall, when durian trees were in full bloom. We sampled the bats attracted to their pale white flowers and were amazed to find six species of fruit bats. We added the dawn bat (Eonycteris major) and Geoffroy’s rousette fruit bat (Rousettus amplexicaudatus) to the list of first recordings from North Pagai Island.
My brief research in North Pagai almost doubled the number of bat species confirmed on the island. Yet many more species likely await discovery and more work is urgently needed to conserve this rich diversity of bats.