Coleura seychellensis, Peters, 1868

Bonaccorso, Frank, 2019, Emballonuridae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 350-373 : 362-363

30 . Seychelles Sheath-tailed Bat

Coleura seychellensis

French: Emballonure des Seychelles I German: Seychellen-reischwanzfledermaus I Spanish: Embalonuro de las Seychelles

Taxonomy. Coleura seychellensis Peters, 1868 ,

Mahé , Seychelles .

Two subspecies are recognized.

Subspecies and Distribution.

. s. seychellensis Peters, 1868 - NW Mahé I.

Extinct on Praslin I.

C. s. silhouettae Thomas, 1915 — Silhouette I. Extinct on La Digue I.

Descriptive notes. Head—body 55-65 mm, ear 14-15’9 mm, hindfoot 8-5-10’3 mm, forearm 51-9—56’4 mm; weight 10-2— 11.1 g. No data available for tail length. The Seychelles Sheath-tailed Bat is sexually dimorphic in size, with females larger than males. Dorsal and chest fur are reddish brown, and fur on venter is slightly paler. Eyes are large and conspicuous. Flight membranes are reddish brown.

Habitat. Coastal boulder fields, native palm woodlands dominated by Nephrosperma van-houtteanum (Arecaceae) , and marsh habitats.

Food and Feeding. The Seychelles Sheath-tailed Bat feeds on insects. On Silhouette Island, the population at Grande Barbe roosts near marshes and feeds heavily on marsh associated Diptera (Ceratopogonidae) , with lesser proportions of Lepidoptera , Hymenoptera , and Coleoptera . A second population roosting in boulder caves near palm woodlands at La Passe feeds primarily in forest gaps. Lepidopterans dominate diet at La Passe, with significant proportions of Hymenoptera and Coleoptera eaten in June-September. In December-March, true weevils in the family Curculionidae (Coleoptera) are the largest part of the diet, with reduced proportions of Lepidoptera and Hymenoptera . Rock overhangs are used as night roosts during pauses in foraging activity.

Breeding. Female Seychelles Sheath-tailed Bats give birth and care for one young in the rainy season (November-December).

Activity patterns. Seychelles Sheath-tailed Bats hang down from ceilings of day roost caves but with all appendages clinging to rock substrates. They appear to roost exclusively in boulder caves, with horizontal ceilings having stable cool temperatures of 25-9 - 28-7°C. Overgrowth of vines of invasive kudzu ( Pueraria phaseoloides , Fabaceae ) that block ingress/ egress from formerly preferred caves appears to cause roost abandonment. Abandoned roosts have been recorded from all four islands in the historical distribution. Foraging activity has been observed throughout the hours of darkness and at dawn concluding at c.06:00 h. Echolocation search calls consist of pulse sequences, with first harmonic peaking at frequencies of 39-2-41 • 1 kHz. These calls have narrow bandwidth and short durations (1-4-3 milliseconds). Search calls allow targeting of aerial prey from relatively long distances.

Movements, Home range and Social organization. Colony size of Seychelles Sheathtailed Bats in modem times appears to vary between two and 40 individuals. A single breeding male will form a harem that includes adult females and dependent young. On Silhouette Island, foraging movements, verified by two independent studies for the population occupying native palm woodland, never exceeded 320 m from the day roost. Insects in woodlands with intact understories were abundant so that this small population did not have to range farther from their roost cave.

Status and Conservation. Classified as Critically Endangered on The IUCN Red List. The Seychelles Sheath-tailed Bat has a very small known population of fewer than 100 individuals, which is declining, and all subpopulations are small. Major threats include introduced predators; loss of habitat, especially from drainage of marshes; and invasive plants that overgrow cave entrances. Historically, it was described as “very common in the neighborhood of the town of Port Victoria” in 1868 and appeared to be abundant up until the 1970s. Subsequently, in large part due to collection of guano deposits in roost caves, population decline might have been as high as 90%. The only known remaining roosts that are occupied are caves at La Passe and Grande Barbe on Silhouette Island and two cave sites on Mahé Island: Cap Temay containing 20-30 individuals and Anse Major with only 1—2 individuals. More recently, the roost cave at La Passe declined from 32 individuals in 2003 to 27 individuals by 2008. It was probably extirpated on Praslin and La Digue islands in the 1980s. The Nature Protection Trust of the Seychelles has monitored the known population ofSeychelles Sheath-tailed Bats since 1997, and this protection has resulted in a population growing from 18 individuals to 40 individuals in 2012. Catastrophic decline probably took place primarily in the late 1800s and early 1900s as lowland forests were cleared and converted to intensively managed coconut plantations, lacking a shrub layer that formerly supported insects. Invasive plants including the kudzu vine overgrowing cave roosts and abandoned coconut plantations farther deteriorated suitable foraging and sheltering sites. Seychelles Sheath-tailed Bats are sensitive to disturbance of roost caves. Predation from introduced common bam-owls ( Tyto alba ) in 1949 and feral cats also have contributed to declines. Conservation actions should include annual census of known roosts; seasonal and annual echolocation surveys at permanent monitoring stations; additional exploration of suitable habitat to attempt to locate additional roost colonies; frequent re-evaluation of status and distribution; legal protection of all known roosting sites and immediate surroundings; control of introduced bam-owls and feral cats; habitat protection of known feeding areas; public awareness campaigns; additional research into distribution, ecology, and threats; removal of invasive vegetation from existing and abandoned roost sites; and restoration of lowland forests via replanting native vegetation where plantations have been abandoned.

Bibliography. Ball (2004), Bambini eta/. (2006), Burgess & Lee (2004), Gerlach (2004, 2009), Gerlach & Taylor (2006), Goodman, Puechmaille eta/. (2012), Hill (1956,1971a), Joubert (2004), Monadjem, Gerlach eta/. (2017), Nicoll & Suttie (1982), NPTS (2003), Rocamora & Joubert (2004), Wright (1868).

Figures

On following pages: 22. New Guinea Sheath-tailed Bat (Emballonura furati); 23. Beccari's Sheath-tailed Bat (Emballonura beccarti); 24. Large-eared Sheath-tailed Bat (Emballonura dianae); 25. Seri'sSheath-tailed Bat (Emballonura sertii); 26. Pacific Sheath-tailed Bat (Emballonura semicaudata); 27. Western Sheath-tailed Bat (Paremballonura tiavato); 28. Peters's Sheath-tailed Bat (Paremballonura atrata); 29. African Sheath-tailed Bat (Coleura afra); 30. Seychelles Sheath-tailed Bat (Coleura seychellensis); 31. Madagascar Sheath-tailed Bat (Coleura kibomalandy); 32. Dark Sheath-tailed Bat (Mosia nigrescens); 33. Chestnut Sac-winged Bat (Cormura brevirostris); 34. Gray Sac-winged Bat (Balantiopteryx plicata); 35. Thomas's Sac-winged Bat (Balantiopteryx io); 36. Ecuadorian Sac-winged Bat (Balantiopteryx infusca).

Subspecies and Distribution. . s. seychellensis Peters, 1868 - NW Mahé I. Extinct on Praslin I. C. s. silhouettae Thomas, 1915 — Silhouette I. Extinct on La Digue I.