Bats

Bats

Bats are among the most misunderstood of all animals, with irrational fears pervading human folklore in many countries, and an almost complete ignorance of the vital role that different species play in the control of insects and the life cycles of fruiting plants.

With over 950 known species, bats are among the most numerous and successful groups of mammals. Their unique (for a mammal) ability of powered flight (the so-called flying squirrels and flying lemurs can only glide) is probably the single most important factor for the success and diversification of bats. These winged creatures occur across the world from the fringes of the Arctic circle to the middle of the great deserts, and even on remote oceanic islands devoid of all other mammals. All bats belong to the Order known as Chiroptera.

Micro and Mega - Two Distinct Groups

The world's bats are divided into two distinct groups or sub-orders: the insectivorous bats or microbats (Microchiroptera) and the frugivorous bats or megabats (Megachiroptera). Fruit bats and insect bats possess a similar pattern of wing webbing between their elongated fingers, but despite this similarity there are numerous differences, which suggest that they have very different ancestors. It is thought that the Microchiroptera may be related to shrews, while the Megachiroptera might have affinities with primitive primates. Confirmation of these relationships awaits detailed investigation of DNA and other attributes.

Flying Foxes

The fruit bats are sometimes known as flying foxes, on account of their dog-like snouts, and the largest species may have a wingspan of close to one metre. In fact, they more closely resemble lemurs (those primitive primates confined to Madagascar) and they have large brown eyes and funnel-shaped ears. Powerful hook-like claws exist on the toes and they have blunt teeth and muscular tongues ideal for processing soft fruits. Males of most species have repetitive clinking calls, and others chatter like monkeys when feeding. Not surprisingly, fruit bats are dependent upon a year-round supply of fruit and the greatest variety therefore, occur in the tropics and sub-tropics, where the stable climate allows trees to bear fruits and flowers in all seasons.

Fruit bats are also very fond of nectar and serve as pollinators for trees such as the baobab and sausage tree. Because they usually spit out fibres, seeds and rind, these bats serve as important agents of seed dispersal and play an important role in reforestation. Some fruit bats are migratory and may visit more temperate regions for part of the year; the Egyptian fruit bat and straw-coloured fruit bat are present in Cape Town, South Africa, between October and March.

Insect-eaters Rely on Echo-location

The Microchiroptera (insectivorous bats) are characterised by small eyes, sharp pointed teeth, and strangely-shaped ears, while many also have bizarre nose structures. Seen up close, most appear somewhat frightening and this appearance has contributed to their unpopularity among many people (see below).

Able to find their way and hunt in complete darkness, insect bats employ ultrasound (inaudible to the human ear) to navigate by echo-location. A call or chirp is made and then "read" as it is reflected back to the animal's highly sensitive ear receptors. Scientists are able to identify and classify bats on the basis of their calls, by using ultrasound equipment, as each has a particular "signature". A distinction is made between "shouters" and "hummers". "Shouters" call through the mouth and "hummers" project sound through their nostrils via nose leaves of various shapes. The majority of Microchiroptera are rather small - some are minuscule - and feed on small or medium-sized winged insects. South America is home to larger varieties, which specialise on frogs, lizards and even fish!

Identification of African Bats

The knowledge of bats is growing constantly as more people specialise in their study and more information is obtained. Nevertheless, it is extremely difficult to identify most species, even if captured, since their physical differences are often minute. For many species, only the distinctive call can be relied upon, although there are several very distinctive bats such as the beautiful, white-bellied Mauritian tomb and the yellow-winged bat, which has pale blue-grey fur and bright yellow-orange wing membranes (this species is fairly common in northern Tanzania, where it is frequently encountered at CCAfrica's Grumeti Exeter River Lodge).

Although specific identification is rarely possible, insectivorous bats can at least be identified to family level providing a reasonable view is obtained. The Kingdon Field Guide to African Mammals has clear illustrations of the sheath-tailed, mouse-tailed, free-tailed, leaf-nosed, vesper, horseshoe, slit-faced and large-winged bat families.

Unfounded Fear and Loathing but Vampire Bats can Spread Rabies

Due to their nocturnal habits, seemingly unpredictable manner of flight, and often ferocious appearance, bats have long aroused irrational fear among people. Bats are frequently associated with human habitation as they roost in roofs and wall cracks, and many fables and myths associate them with demons, or with the Devil and Hell. The existence of the vampire bat in tropical America has added fuel to these superstitions. This species feeds on the blood of sleeping mammals (particularly cattle and pigs). It is also a known vector of the deadly rabies virus, so it is feared with good reason by stock farmers. Sadly, indiscriminate "control" by poison baits has led to the massacre of harmless species, many of which play a crucial role in pest control and flower pollination.

Apart from direct persecution, bats are also susceptible to changes in their habitat and food availability brought about by man's modification or destruction of the environment. Several species can be regarded as endangered or vulnerable. Because new species are constantly being described and named, it is possible that some may have become extinct in recent years and large parts of south-east Asia and South America have been cleared of tropical forest. Bats are also at risk to chemical sprays used to control malaria, which may contaminate or eliminate their food source.

Conservation

A knowledge of the important function that all African bats play in the various habitats they occupy is crucial to their survival at the hand of man. Although the existence of a sizeable bat colony in the roof of a house is unhygienic, the presence of small numbers poses no harm. Some bat-friendly people have even constructed "bat hotels" (a divided wooden box on a raised pole) to encourage colonies to roost away from living quarters. Mosquitoes are among the primary prey of many insectivorous bats and huge numbers of these potentially dangerous insects can be consumed by a thriving bat population.

Posted: Mammals by CC Africa, Date: 21 November 2006