Seychelles sheath-tailed bat (Coleura seychellensis)

KingdomAnimalia
PhylumChordata
ClassMammalia
OrderChiroptera
FamilyEmballonuridae
GenusColeura (1)
SizeHead-body length: 55 – 65 mm (2)
Male weight: 10.2 g (2)
Female weight: 11.1 g (2)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

The Seychelles sheath-tailed bat is one of the world’s rarest mammals. These small bats are a reddish-brown colour with paler underparts (2). The name ‘sheath-tailed’ refers to a membrane that extends between the hind legs and can be placed over the tail. This provides precise movement in flight between the rainforest trees of their habitat (3).

Endemic to the Seychelles islands of Mahe and Silhouette in the Indian Ocean, with historical records also from Praslin and La Digue islands (4). Total numbers are thought to range between 30 and 100 individuals (5).

Roost sites are located in coastal boulder field caves with stable cool temperatures and access to palm woodland or marsh habitat (4) (6).

Until recently very little was known about this rare Seychelles bat. Colonies roost in caves and are thought to be divided into harem groups that consist of adult females and their young and are led by a single male (2). Unlike the African sheath-tailed bat C. afra (2), the Seychelles species hangs upside down from the cave ceiling to roost. Females give birth to their offspring during the rainy season that runs from November to December (2). These bats feed exclusively on insects (3) (7) (8).

The Seychelles sheath-tailed bat has been lost from the majority of islands where it was originally found. The precise cause of this dramatic decline is unclear; it has been speculated that introduction of the predatory barn owl (Tyto alba) and declines in insect availability resulting from use of pesticides may be involved (3). However, the recent discovery of a second roost near marshes on Silhouette showed that the bats here feed on different insects than those eaten by roosts that forage in palm woodlands elsewhere (4). It has therefore been argued that this variability in the diet demonstrates that food is not a limiting factor for the species, and the decline in the species may rather be attributable to habitat alteration caused by invasive plants obstructing roost entrances (4).

The Nature Protection Trust of the Seychelles has monitored the known population of Seychelles sheath-tailed bats since 1997 (5) (6). As with other bats, the protection of roosts and foraging habitat are of great importance. Existing roosts must be preserved, not only from human disturbance, but also from introduced plant species that smother the cave entrances (4). To this end, one roost site had the invasive Kudzu vine Pueraria phaesolides cut back from its entrance in 2001 and 2004, and ongoing management aims to completely remove the species from the area (4). It is hoped that removal of invasive creepers from existing and abandoned roost sites will help to increase the desperately low numbers of this critically endangered bat to more sustainable levels.

For more information on this species see:

Authenticated (24/04/2006) by Justin Gerlach. Scientific Co-ordinator, The Nature Protection Trust of Seychelles.
http://islandbiodiversity.com

  1. IUCN Red List (April, 2006)
    http://www.iucnredlist.org
  2. Walker’s Mammals of the World (July, 2003)
    http://www.press.jhu.edu/books/walkers_mammals_of_the_world
  3. Animal Info (July, 2003)
    http://www.animalinfo.org/species/bat/coleseyc.htm
  4. Gerlach, J. and Taylor, M. (2006) Habitat use, roost characteristics and diet of the Seychelles sheath-tailed bat Coleura seychellensis. Acta Chiropterologica, 8(1): 129 - 139.
  5. Gerlach, J. (2004) The bats of Silhouette island, Seychelles. Phelsuma, 12: 78 - 90.
  6. Nature Protection Trust of Seychelles (July, 2003)
    http://islandbiodiversity.com
  7. Joubert, F. (2004) A preliminary investigation into the general ecology, status and habitat of the Seychelles sheath-tailed bat Coleura seychellensis (Emballonuridae). Phelsuma, 12: 54 - 68.
  8. Burgess, H. and Lee, N. (2004) A behavioural study of the Silhouette sheath-tailed bat (Coleura seychellensis). Phelsuma, 12: 69 - 77.