Hipposideros commersoni
Commerson's roundleaf bat

Giant leaf-nosed bats, also known as Commerson's leaf-nosed bats, are distributed throughout equatorial Africa and on the island of Madagascar. Recent studies have divided the species into 5 subspecies based on distinct regions of occurrence. Hipposideros commersoni commersoni is found only on the island of Madagascar. Hipposideros commersoni thomensis is located on the islands of Principe and Sao Tome. Hipposideros commersoni gigas is primarily located in western regions of equatorial Africa. Hipposideros commersoni niangarae is located only in the Niangara Region of the Congo. Hipposideros commersoni marungensis has the largest range and is found from East Africa to South Africa and Namibia. (Kingdon, 1984; Nowak, 1999)

Commerson's leaf-nosed bats are known to prefer areas of edge habitat. Such areas provide perches along the corridors the bats use to travel. Large congregations occur in regions of dolomite because of the caves formed. In other regions smaller colonies are located in small caves and in hollow trees. (Vaughan, 1977)

Commerson's leaf-nosed bats are among the largest insectivorous members of the suborder Microchiroptera, ranging in weight from 40 to 180 g when mature. Lengths are reported at between 110 and 145 mm, and wingspans between 540 and 560 mm are recorded. Males are typically larger than females. Distinct skeletal characteristics of the species include a large sagital crest that is more prominent in males. Large canines and stout mandibles are other characters of the skull which are useful in identification. Pelage color ranges from a pale-grey to reddish-grey with tawny underparts. An elaborate nose leaf and falcate ears rounded near the tip distinguish H. commersoni. (Kingdon, 1984; Nowak, 1999)

No data for H. commersoni could be found, however, other members of the genus have been aged to at least twelve years old based on band recovery data. This species is probably similar in longevity to other members of the genus. (Nowak, 1999)

Commerson's leaf-nosed bats are colonial bats often found in caves. Members of both sexes are known to enter torpor when unfavorable environmental conditions exist. This is most common during periods of low prey availability. When roosting, the bats are spaced slightly apart at a wing-tip distance. This slight territorality is found in both sexes. When roosting and disturbed, a shrill audible alarm call is made. Females have two annual migrations within the region which are likely caused by interspecific competition for food during periods of high nutritional demand. (Cotterill and Fergusson, 1999; Kingdon, 1984)

In general, members of the genus Hipposiderus are known to roost in trees, buildings, and caves. These animals are nocturnal, and, like all bats, are able to fly. Hipposideros is known to fly lower than most bats, catching insects, such as beetles and cicadas, using the sounds made by the prey animals to locate them. Members of this genus do use echolocation in catching prey also, and seem to be somewhat specialized to short-range hunting with calls emitted from the nostrils. (Nowak, 1999)

Home Range

Home range size for this species has not been reported. (Nowak, 1999)

Communication in this species has not been fully described. Members of the genus Hipposideros are known to have some vocalizations. They echolocate to capture prey in addition to using the noises made by the prey themselves. It is likely that tactile communication occurs within the roost, between offspring and the mother, and between mates. Olfaction is typically important in mammals, and may play some role in identifying individuals or reproductive conditions in this species. Although these bats have eyes, most microchiropterans are not known for their well developed visual abilities. (Nowak, 1999)

Commerson's leaf-nosed bats use their powerful jaws and sharp canines to catch and consume large beetles. The bats have evolved two different strategies to capture prey: Sedentary observation and collection, and hunting actively during flight. The sedentary perching involves flying to a known roost and scan the area. When prey is observed, the bat flies from the perch to collect it, then returns to the roost to consume the prey item. The second strategy involves actively searching for the prey by flying at a level of about 2 meters actively echolocating for prey on the ground. (Vaughan, 1977)

Bat hawks are reported to be predatory on these bats. It is likey that other small mammals and snakes may prey on this species as well. Vulnerability to predation is often highest for bats as these animals emerge from roosting sites. (Nowak, 1999; Vaughan, 1977)

Because H. commersoni feeds primarily on beetles and has very few natural predators, we can speculate that this species is near top of of the food chain but does not occupy the keystone species niche in its woodland habitat. Commerson's leaf-nosed bats might have a slightly larger ecological role in the cave ecosystem, into which the bats bring large amounts of nitrogen. (Vaughan, 1977)

There are no known adverse affects of H. commersoni on humans

Roosting caves of H. commersoni in some regions of equatorial Africa have very high densities of bats, and have been inhabited by these animals for many, many years. The feces, or guano, from the bats is important commercially in these areas as a source of nitrogen for fertilizers. (Cotterill and Fergusson, 1999)

The conservation status of these animals remains unknown. Although over 34 members of the genus Hipposideros are listed as endangered, vulnerable, or threatened by various agencies, H. commersoni is not listed by CITES or IUCN. (Nowak, 1999)