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THE BAT INTEREST GROUP
OF KWA ZULU NATAL
Copyright (C) 2011 Bat Interest Group of KwaZulu Natal All Rights Reserved
Copyright Paul Buchel
BATLINE 082 445 0585

THE TRUTH ABOUT BATS

 

Bats are small, nocturnal, and shy of humans; although there are many bats in our environment most people never come into contact with them and are unaware that the night skies are often filled with the sounds made by these fascinating creatures.

 

There are over 1200 kinds of bats in the world - the second most diverse group of mammals, only rodents have more – ranging from the large flying foxes of Australasia with wing spans of up to 1.6 m to the tiny pipistrelle bats which weigh less than a R2 coin. We are lucky enough to have 58 species of bats in South Africa: unfortunately, two thirds of the species assessed for the South African Red Data Book (a list showing how close to extinction a species is) are listed as “Near Threatened to Critically Endangered”. In KwaZulu-Natal three species are of especial concern: the Short-eared Trident bat is known from only one colony in the north of the province, Rendall’s serotine is also known from only one place, and the Large-eared free-tailed bat is found only in the greater Durban area and so far only in house roofs. 

 

Bats in South Africa can be separated into two groups: the bigger fruit bats and the smaller insect bats. Fruit bats have long noses typical of animals with a good sense of smell, big eyes (and thus excellent eyesight), and no tail. They are never found IN roofs, although they are often found around houses, typically in trees but sometimes hanging on the eaves. Insect bats are smaller - some can sit quite comfortably on the end of your thumb – and often have strange face structures which signify their incredible ability to navigate using sound, a process known as echolocation. All insect bats have tails.

 

Nearly all bats eat either fruit or insects – a handful of species eat other things such as scorpions, small fish, and frogs. Only the vampires of central America eat blood: vampire bats have suffered much bad press owing to the book Dracula and its many spin-offs, but vampire bats are actually very small (less than 50 g) bats with a strong social structure.

 

More than any other group of animals, people have developed many strange myths about bats. Bats are not blind, all have eyes and can see, and many can see extremely well. Bats do not get stuck in your hair, burrow under your skin, or chew your ears. In fact, bats are amongst the gentlest wild mammals in the world.

 

Being mammals, bats have fur, bear live young, and the mothers feed the babies milk as any mammal mother. Bats usually have only one baby a year, although in the warmer parts of this country in good years some mothers may have another in the second half of summer. Bat babies are called pups and are born pink, hairless, and with small stubby wings. They cannot fly for the first few weeks of life and at this time are unable to leave their roosts.  Fruit bat mothers generally carry their young with them at night; insect bats usually leave them in a safe roost and return at intervals to feed.

 

With only one baby a year, and because the difficulty of learning the skills needed to be a successful flyer means there is a very high death rate amongst the young, bats have some of the slowest reproductive rates of any small animal. To balance this, bats have also the longest life spans of any small mammal: there are several records of bats living longer than 40 years.

Most bats are highly social: they live in stable colonies and many retain life-long bonds with their mothers. Colony sizes vary from the many thousands of cave-dwelling long fingered bats to sheath-tailed bats, which roost singly or in mother-daughter pairs. Occasionally adult male bats live alone.

 

The insect-eating bats have a very specialized ability to save energy when food is short or the temperature is very cold: they can “reset” their metabolic rate in a process known as torpor. A bat undergoing torpor chooses a safe roost site and in effect falls into an extremely deep sleep. Its heart rate slows, its breathing rate reduces, and its body temperature drops. When the bat “sleeps” like this throughout winter it is known as hibernation. A torpid bat moves very slowly, as if it is moving through syrup, and before it can fly it has to warm itself. Many of our insect bats warm slowly throughout the afternoon to be ready to fly in the evening; a bat which is disturbed during the day has to warm itself rapidly by shivering. Disturbing a hibernating bat can cost it its life, as the emergency warming process is very expensive energetically: each warming costs the equivalent of 8 to 30 days of fat reserve. If the bat runs out of its fat reserves before winter is over and the insect numbers have returned, it may starve.

 

Bats are very clean animals: they groom themselves meticulously using their hind feet as combs. They carry very few parasites, all of which are specialized for their bat hosts: none have been known to transfer themselves to humans and they carry no known disease.

 

The importance of bats to our environment cannot be overemphasized. Because they are small and nocturnal the impact they have is largely undocumented, but the world as we know it would be very different without our bats. Insect-eating bats are the major predators of night-flying insects, which include most crop pests. In the USA it has been estimated that the free-tailed bats of south-central Texas eat 1 000 TONS of insects per night, mostly corn earworm and tobacco budworm moths, and fly to heights of up to 3,000 meters to do it. In this country no study has yet been undertaken of the impact of our bats, but it is probable that they are eating similar amounts. The droppings of insect-eating bats are known as guano and can be used as an extremely good organic fertilizer.

 

Fruit bats rarely eat fruit while hanging in the fruiting tree: they take a mouthful of fruit and fly to another site to eat it. After chewing the fruit and swallowing the juice they spit out the seeds and pulp. While this habit annoys many patio owners, it is essential for the regeneration of forests: it has been estimated that 95% of the new trees in tropical rainforest in Africa come from seeds dropped by fruit bats. Fruit bats are also the pollinators of many African trees, including the Baobab and the Iroko tree.

 

Bat numbers the world over are dropping due to human intolerance, pesticide misuse, and the removal of indigenous vegetation. Bats do not have to be a problem to humans: with the correct knowledge we can learn to appreciate the role they play and live our lives without impacting on theirs.

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