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The small slit-faced bat, which can be found throughout East Africa, is one of two species of slit-faced bats found on Zanzibar. They are pale brown in color and are 30-40 mm in length with pointed tragi (protuberances in the inner ear). Both species of echolocation call are short, constant frequency calls of 36-45 kHz. The Zanzibar slit-faced bat echolocates at a frequency of 37 kHz, unlike Neoromicia nanus which has a frequency of 35 kHz. It roosts in caves, old beach wells and the spaces under roofs during the day. This species has been studied by various researchers in relation to its diet and calls, but little has been done in the way of conservation. It is found throughout the main islands in a variety of habitats and is not threatened. This species is believed to be a close relative of the free-tailed bat Tadarida aloysiae due to similarities in skull and dental morphology.
The Zanzibar slit-faced bat (Nycteris spp.) is a medium-sized insectivorous bat with a wingspan of up to 80cm. The name is derived from the unusual slit which runs down the length of the face. The nose is peculiarly long and the ears are pointed and erect, the color can range from brown to nearly white. They have a keeled calcar and the tail extends free from the uropatagium. This is a genus of medium-sized bats with long narrow wings and long pointed tragi. Nycteris occur widely across Africa and are one of the most diverse bat families. Nycteris has a wide range of species that have yet to be fully classified and an unidentified number of subspecies. Nycteris are found in a variety of habitats and are known to be able to exploit human settlements as a result some Nycteris are threatened by habitat destruction.
Another unusual adaptation is that in times of food shortage, the bat is able to reduce its body size (and food requirement) by going into a torpor. An unusual behavior for a tropical mammal which is not faced with the problems of hibernating temperate species. This is achieved by the bat reducing the energy consumption of all its internal organs and dropping its body temperature to just above that of its surroundings. It will remain in this state for several days, emerging to normal activity if it manages to restore adequate fat reserves. This has interesting connotations for the conservation of the species that live in tropical islands under siege from invasive species, as it allows the bat to survive in times of reduced food availability.
Their diet also reflects their habitat as they are one of only 3 species of African bat that are blood feeders. The bats, of which there are 4 species, also consume large quantities of fruit and will on occasion eat insects. Blood-feeding is a highly successful dietary specialization as blood is an abundant and relatively predictable food source compared with the availability of fruit or insects. The bats find their food by foraging and have been noted to fly 2.5km to a feeding area, with studies being done to determine which specific method of tracking down the food source.
The adaptations of the Zanzibar Slit-faced Bat are many and various and are an excellent example of how a mammal has evolved to fit into a specific niche in the ecosystem. The roosting habits of the bat are unusual as it is one of only a few species of bat that roosts in caves during the dry season. It will then seek out a more humid microclimate to hibernate during the rains. In captive situations or in the field where microclimates can be manipulated, the bats will without fail seek out the area of the cave with the highest humidity.
There are only two caves in which to look for the Zanzibar Slit-faced Bat. The first and generally the easiest to visit is located near the village of Kizimkazi on the southwest coast of the island. Visits can be arranged in Kizimkazi (usually through a local villager who holds the key to the cave) and the bats can be found at any time of day roosting on the roof of the cave or on the overhanging ledge. The cave is quite large and the bats are generally easy to approach for close observation. They are quite accustomed to humans and will often allow close approach as they are confident in the protection offered by the cave. This site offers excellent photographic opportunities. The second cave is located in the Kiwengwa/Pongwe area of the northeast coast. This cave is more difficult to find (local information will be needed to locate it) and it is a bit of a scramble to reach but it is worth the effort. The bats are generally roosting deeper inside this cave but can be seen from the entrance way. The Zanzibar Slit-faced Bat is also widely reported to roost in the large and now largely abandoned coral rag buildings that were once used as lodgings in the late 19th/early 20th century. These buildings are found in various locations around the island. Due to the nature of the construction of these buildings (with large open roof spaces) and their now secluded and quiet location they offer excellent habitat for the bats. With time and patience one can still locate these bats roosting in such structures. An example are the old lodgings at Fukuchani (near Nungwi) which can be visited as a curiosity in their own right.