Oryx Vol 40 No 3 July 2006 Another Seychelles endemic close to extinction: the emballonurid bat Coleura seychellensis Laura Bambini, Andrew Blyth, Tim Bradford, Rachel Bristol, Sarah Burthe, Louise Craig, Nick Downs, Sinclair Laing, Lorraine Marshall-Ball, Denise McGowan, Terence Vel and Paul Racey Abstract The only microchiropteran endemic to the and their echolocation calls were also characteristic of granitic Seychelles, the sheath-tailed bat Coleura bats feeding in open habitat. This study provides no seychellensis, is categorized as Critically Endangered on evidence that C. seychellensis is dependent on forest the IUCN Red List. Using bat detectors, the islands of or wetland for foraging. Dietary analysis indicated that Mahe´, Praslin and La Digue were surveyed to establish C. seychellensis feeds on Coleoptera, Lepidoptera and the current distribution of this species. Although two Diptera. A public education programme to highlight the new roosts were discovered on Mahe´, no bats were conservation status of the bat and the consequences of observed on Praslin and La Digue, and the range of roost disturbance is recommended, together with the C. seychellensis appears to have further contracted in the urgent need for legal protection of the bats and their last 2 decades. A total of 19 C. seychellensis were counted roosts. emerging from or entering three roosts in boulder caves on Mahe´ during 18 evenings of observations. The bats Keywords Coleura seychellensis, dietary analysis, foraged in open coastal habitat, some of it anthropogenic, distribution, echolocation, roosts, Seychelles. Introduction foraging habitats or other aspects of its ecology (Gerlach, 1997, 2004; Hutson et al., 2001). It is sexually dimorphic, The endemic sheath-tailed bat Coleura seychellensis is the with females (10–12 g) larger than males (c. 10 g), and is only microchiropteran found in the granitic Seychelles. a long-winged fast-flying species with high aspect ratio Historically recorded as abundant (Wright, 1868), the and wing loading (Nicoll & Suttie, 1982). current population has been estimated at 50–100 Surveys in 1972, 1974 and 1976 found bats in low num- individuals (Gerlach, 1997; Rocamora, 1997). The species bers in a boulder cave in Jardin Blanc, La Digue (Racey & is categorized as Critically Endangered on the IUCN Red Nicoll, 1984), and a maximum of 12 bats was counted in List (IUCN, 2006) based on criteria C2a(i, ii), which a cave on Praslin in June 1980 (Nicoll & Suttie, 1982). Bats indicates that the small population size and rate of were sighted on Mahe´ in 1993 and 1994 (Matyot, 1995) decline are of great concern and likely to result in and a Glasgow University Expedition found bats on the extinction unless action is taken. Apart from studies on a west coast of the island in 1996, together with a single colony of C. seychellensis on Silhouette, there is little individual on Praslin but none on La Digue (Mellanby information on the species’ distribution, roosting and et al., 1996). Joubert (2004) reported sightings of foraging bats on Mahe´ and an occupied roost on Silhouette. The Laura Bambini, Andrew Blyth, Tim Bradford, Louise Craig, Sinclair Laing, Silhouette population is reported to have increased since Denise McGowan and Paul Racey (Corresponding author) School of 2001, and currently numbers 32 (Gerlach, 2004). The Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK. older residents of Mahe´ recall seeing the bats in greater E-mail [email protected] numbers, and in areas now abandoned by bats, until the Sarah Burthe Population Ecology Research Group, University of Liverpool, 1960s (pers. comms), and residents from Silhouette have Leahurst, Chester High Road, CH64 7TE, UK. reported that bats were abundant until the late 1970s Lorraine Marshall-Ball School of Biology, University of St Andrews, Fife, (Joubert, 2004). KY16 9TS, UK. In accordance with the specific research needs identi- Nick Downs Cresswell Associates (Environmental Consultants) Ltd, The Mill, fied for C. seychellensis in the Microchiropteran Action Brimscombe Port, Stroud, Gloucestershire, GL5 2QG, UK. Plan (Hutson et al., 2001), the aim of the present study Rachel Bristol and Terence Vel Nature Seychelles, The Environment and was to survey the granitic islands of Mahe´, Praslin and Education Centre, Roche Caiman, PO Box 1310, Victoria, Mahe´, Seychelles. La Digue for C. seychellensis in an attempt to locate roosts, Received 9 May 2005. Revision requested 19 September 2005. to establish the bats’ foraging habitat and diet, and to Accepted 29 March 2006. assess its conservation status. 310 ß 2006 FFI, Oryx, 40(3), 310–318 doi:10.1017/S0030605306000809 Printed in the United Kingdom Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.139, on 25 Sep 2021 at 10:11:08, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605306000809 The emballonurid bat Coleura seychellensis 311 Materials and Methods between 18.30 (dusk) and 19.30. Additionally, car sur- veys were carried out twice, driving around the coastal Field work was carried out during the dry season (June– road at slow speed and holding a bat detector out of the September) of 2004, when members of the Bats on the windows on each side. Batbox III detectors (Batbox Ltd, Brink 2004 Expedition were resident on Mahe´; 6 days West Sussex, UK) were used for all surveys, set to a were spent on Praslin and 4 days on La Digue. Internal frequency of 40 kHz (Nicoll & Suttie, 1982). restrictions meant that it was not possible to visit Silhouette. Roost searches Distribution Because roosts had previously been reported in boulder Bat detector surveys were carried out on foot during June caves (Nicoll & Suttie, 1982), roost searches were carried and July. On Mahe´ 26 2-km transects were surveyed so out in boulder fields near the areas where bats were fre- that all types of habitat (coastal, low altitude forest and quently heard on bat detectors. The team was informed of upland forest) were included (Fig. 1). Transect h in Port the location of one roost, in Anse Major. Searches for Launay (Fig. 1) included a 200 m stretch along the edge of additional roosts were conducted at dusk and dawn, a small mangrove swamp, and an upland marsh in the during a 2-day period in Port Launay and a 6-day period Morne Seychellois National Park was surveyed on one in Baie Lazare on Mahe´. During these searches obser- occasion. In particular, areas where sheath-tailed bats vers with bat detectors were positioned 50–100 m apart were previously reported by Mellanby et al. (1996) were around an area with a suspected roost. Times of bat surveyed. Because of the extent of human development passes were recorded, and by comparing the times when on the islands, and because much of the terrain was different observers encountered the bats the suspected difficult, transects were restricted to roads and footpaths. roost location was reassessed and the observers moved Each transect was walked twice, on different nights, closer to the putative roost location for the next search. Fig. 1 The 26 transects on Mahe´ (a–z), surveyed on foot with bat detectors between June and September 2004. C. seychellensis was found on six transects (d, e, f, k, t & v). Three roosts are known, from the Anse Major, Baie Lazare and Port Launay districts. The filled boxes mark the five known bat feeding sites. The shaded area refers to the approximate extent of Morne Seychellois National Park. ß 2006 FFI, Oryx, 40(3), 310–318 Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.139, on 25 Sep 2021 at 10:11:08, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605306000809 312 L. Bambini et al. Boulder fields were also searched during daylight for from the north to the south of the island. Three of these potential bat roosts. Because of the species’ threatened transects were coastal and at low altitude, following status, roosting bats were not disturbed. roads or trails. One transect, in the south of the island, was on a hill at 150–250 m altitude. No bats were encoun- Bat activity tered on the more developed east coast. Three of the transects on which bats were found (d, e, f; Fig. 1) were at A total of 7 all-night observations were made at the three the edges of the Morne Seychellois National Park, but known roosts on Mahe´ to determine times of activity and the other areas where bats were found are susceptible feeding rates and to assess the importance of roost to further human development. Individual bats were surroundingsasforaginghabitat.Foragingdatawere occasionally encountered inside the National Park, on collected using Batbox III bat detectors and stopwatches. the footpath to Anse Major (transect e). The duration of the bat passes (from when a bat orienta- Bats were mostly seen flying over roads, either tion call was first heard to when it was last heard) commuting or foraging, at a height of 2–10 m. Foraging was noted, and the numbers of feeding buzzes (a series of bats were encountered in five localities (Fig. 1), most rapidly repeated calls emitted in a sequence with frequently at Port Launay. Usually only one bat was seen decreasing pulse intervals, preceding prey capture) were at a time, although in Port Launay and Anse Major bats counted. were occasionally seen in pairs. Bats were also observed Three nights were spent at both the Anse Major and flying up to the canopy and flying along the coast at the Port Launay roosts, and 1 night at the Baie Lazare water’s edge. Bats were present in developed areas near roost.