Comoro rousette (Rousettus obliviosus)

Also known as: Comoros rousette
GenusRoussettus (1)
SizeWingspan: 40 cm (2)
Weight44 g (3)

The Comoro rousette is classified as Vulnerable (VU) on the IUCN Red List (1).

One of the smallest species of fruit bat in existence, the Comoro rousette (Rousettus obliviosus) is a little known species. Thick, dull, grey-brownish fur covers the body, while its facial features are fox-like. The Comoro rousette has a very bright, rose-coloured eyeshine when reflected by light (3).

Species in the genus Rousettus are unique among fruit bats due to their ability to use echolocation. The Comoro rousette has been observed to emit faint but audible clicking sounds during flight, within caves and when foraging. This species also uses loud vocalisations within the roost sites (3).

The Comoro rousette is endemic to the Comoros Islands in the Indian Ocean, where it inhabits only three of the four islands: Grande Comore, Anjouan and Mohéli. This species is restricted to roosting at low elevations (1).

The Comoro rousette is a lowland forest-dwelling species that roosts in caves. It is believed that the entire Comoro rousette population resides in only six remote caves across the three islands, which are surrounded by dense vegetation (1).

Comparatively little is known about the elusive Comoro rousette; however, some studies into its social, roosting and feeding behaviours have been undertaken (3).

Similar to many species of bat, the Comoro rousette roosts in large colonies. Aggregations of this species have been recorded to number between as little as 100 and as many as 13,000 individuals. Within these roosts, the Comoro rousette forms tight clusters containing 50 to several hundred bats. The bats are highly active within the roost, grooming, fighting, spending time scratching, and searching for better positions within the colony (3).

A nocturnal species, the majority of the individuals within the roost do not leave the protection of the cave until just before sunset. The Comoro rousette will spend much of the night foraging and feeding, although some individuals may return to caves early, followed by the remaining colony at sunrise (3).

The Comoro rousette is largely frugivorous; however, flowers and leaves are also included in its diet (3). This species is extremely manoeuvrable, and while foraging for food, the Comoro rousette exhibits unusual flight behaviour, hovering in front of the fruit from which it then feeds. This is fairly rare behaviour for fruit bats as hovering requires large amounts of energy (3).

Not much is known about the breeding biology of the Comoro rousette, although it is likely to be similar to other Roussetus species. The gestation period is likely to be between four and five months, with lactation lasting for a period of about three months. It is possible that the Comoro rousette may give birth more than once a year (4).

The Comoro rousette has a relatively small range, and is known from only six roost sites. With so few roost sites, the loss of just one could have a significant impact on the entire population (3). Currently, the main threat facing the Comoro rousette is human interference. Cave-roosting fruit bats are particularly susceptible to human disturbance, and human activity has also been noted to impact the behaviour of the Comoro rousette (3).

The impact of human activity on the behaviour of the Comoro rousette has been observed by locals. With the human population on the islands increasing, this could potentially pose a problem to this species in the future (3).

Deforestation is a major threat to this species, with high levels seen throughout the Comoros Islands. Increasing deforestation may reduce the food availability for this species, but also native forests can provide protection for fruit bats from changes in the environment, including droughts and cyclones (3).

At present there are no known specific conservation programmes for the Comoro rousette (1). The human impact on the population is currently minimal, as the caves are surrounded by dense vegetation and are not easily accessible. However, ensuring that human activity remains limited around roost sites, and protecting trees and other vegetation around cave entrances should be the focus of future conservation efforts (3).

A number of locals have already been trained to carry out a monitoring program for Livingstone’s flying fox (Pteropus livingstonii), and this could be extended to help carry out surveys of the Comoro rousette to identify new roost sites and monitor population numbers (3).

More information on the conservation of fruit bats:

Find out about conservation on the Comoros Islands:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:

  1. IUCN Red List (December, 2010)
  2. Western Indian Ocean Regional Group - Comoro rousette (December, 2010)
  3. Sewall, B.J., Granek, E.F. and Trewhella, W.J. (2003) The endemic Comoros Islands fruit bat Rousettus obliviosus: ecology, conservation and Red List status. Oryx, 37(3): 344-352.
  4. Reason, P.F., Trewhella, W.J., Davies, J.G. and Wray, S. (1994) Some observations on the Comoro rousette Rousettus obliviosus on Anjouan (Comoro Islands: Western Indian Ocean). Mammalia, 58(3): 397-404.