Interesting Facts about Bats

 

Amazing Bat Trivia - Summary

• The world's smallest mammal is the bumblebee bat of Thailand, weighing only 2g.
• Giant flying foxes that live in Indonesia have wingspans of nearly 2m.
• The common little brown bat of North America is the world's longest lived mammal for its size, with life-spans sometimes exceeding 32 years.
• Mexican free-tailed bats sometimes fly up to 4 km high to feed or to catch tail-winds that carry them over long distances at speeds of more than 96 miles (150 km) per hour.
• The pallid bat of western North America is immune to the stings of scorpions and even the seven-inch centipedes upon which it feeds.
• Fishing bats have echolocation so sophisticated that they can detect a minnow's fin as fine as a human hair, protruding only two millimetres above a pond's surface.
• African heart-nosed bats can hear the footsteps of a beetle walking on sand from a distance of more than six feet.
• Red bats that live in tree foliage throughout most of North America can withstand body temperatures as low as 23 degrees F (-5°C) during winter hibernation.
• Tiny woolly bats in West Africa live in the large webs of colonial spiders.
• The Honduran white bat is snow white with a yellow nose and ears. It cuts large leaves to make "tents" that protect its small colonies from jungle rains.
• Disk-winged bats of Latin America have adhesive disks on both wings and feet that enable them to live in unfurling banana leaves (or even walk up a window pane!).
• Frog-eating bats identify edible from poisonous frogs by listening to the mating calls of male frogs. Frogs counter by hiding and using short, difficult to locate calls.
• Vampire bats adopt orphans and have been known to risk their lives to share food with less fortunate roost-mates.
• Male epauletted bats have pouches in their shoulders which contain large, showy patches of white fur that they flash during courtship to attract mates.
• Mother Mexican free-tailed bats find and nurse their own young, even in huge colonies where many millions of babies cluster at up to 500 per square foot (5000 per square meter).
• A colony of 150  bats can protect local farmers from up to 33 million or more rootworms each summer.
• The 20 million Mexican free-tails from Bracken Cave, Texas eat approximately 200 tons of insects nightly.
• Tropical bats are key elements in rain forest ecosystems which rely on them to pollinate flowers and disperse seeds for countless trees and shrubs.
• In the wild, important agricultural plants, from wild bananas, breadfruit and mangoes to cashews, dates, and figs rely on bats for pollination and seed dispersal.
• Tequila is produced from agave plants whose seed production drops to 1/3,000th of normal without bat pollinators.
• Desert ecosystems rely on nectar-feeding bats as primary pollinators of giant cacti, including the famous organ pipe and saguaro of Arizona.
• Bat droppings in caves support whole ecosystems of unique organisms, including bacteria useful in detoxifying wastes, improving detergents, and producing gasohol and antibiotics.
• An anticoagulant from vampire bat saliva may soon be used to treat human heart patients.
• Contrary to popular misconception, bats are not blind, do not become entangled in human hair, and seldom transmit disease to other animals or humans.
• All mammals can contract rabies; however, even the less than a half of one percent of bats that do, normally bite only in self-defence and pose little threat to people who do not handle them.

Scientific Bat Facts

ORIGINS

Bat fossils date back to around 50 million years ago and are, interestingly, almost identical to those found today.  Before humans began to affect their numbers, bats were once much more common and must have dominated the night skies in some places.
 
Bats are classified as mammals as they have hair, give birth to live young and feed these young on milk produced in mammary glands.  They are the only true flying mammals and are so unique that they have been placed in an order of their own: Chiroptera (meaning ‘hand-wing).  Zoologists recognize two groups of bats, Microchiroptera (insectivorous bats) and Megachiroptera (Old World fruit bats – also called flying foxes).  Insectivorous bats are smaller, with one wing claw and a tail, and are found worldwide.  Fruit bats are larger, with two claws on the wing, a poorly developed or absent tail, a dog-like face and are limited to warmer tropical and subtropical regions (including South Africa).
 
Bats have certain primate affinities, such as giving birth to poorly developed young which are nursed from a pair of pectoral breasts.  Linnaeus, the father of taxonomy, even placed bats in the same group as primates.  Today, scientists generally agree that primates (humans, apes and monkeys) and bats share a common shrew-like ancestor but belong to different groups.

DIVERSITY AND DISTRIBUTION

The 977 species of bats make up a quarter of all mammal species, and are found throughout the world except for the most extreme desert and polar regions.  The majority of species occupy tropical forests, with far fewer species found in colder temperate regions.  Seventy-five species occur in southern Africa, of which 56 occur in South Africa and at least 19 are known to occur in Gauteng and many more in the Northern Region area (considerably more than the 16 species found in the whole of Britain).
 
Bats come in an amazing variety of sizes and appearances.  The world’s smallest mammal, the hog-nosed Bat from Thailand, weighs only 2g.  Some of the flying foxes have wingspans of almost 2m, and weigh up to 1.2kg. The big-eyed, friendly appearance of flying foxes often surprises people who would never have thought bats could be attractive.  Some bats have long angora-like fur, ranging in colour from bright red or yellow to jet black or white.  One species is furless, and another even has pink wings and ears.  A brightly patterned species occurring in South Africa is known as the Butterfly Bat, Glauconycteris variegata.  Others have enormous ears, nose-leaves and intricate facial features that may seem bizarre at first, but become more fascinating than strange when their sophisticated role in navigation is explained.

NAVIGATION, HIBERNATION AND MIGRATION

Like dolphins, all insectivorous bats (and one group of cave dwelling fruit-bats) communicate and navigate using high-frequency sounds, enabling them, in total darkness, to detect obstacles as small as a human hair.  Sounds are emitted in the ultrasonic range from 20 to 210 kHz (frequencies of up to about 16kHz are audible to humans) from either the mouth (e.g. vesper bats: Family Vespertilionidae) or the nose (e.g. horseshoe bats: Family Rhinolophidae).  The echolocation system of bats is immensely sophisticated, and, on a watt-per-watt, gramme-per-gramme basis has been estimated to be literally billions of times more efficient than any system devised by man.  In addition, bats are not blind and many have excellent vision.
 
In temperate regions (and even sometimes in subtropical regions like parts of South Africa) cold winters force bats to migrate or hibernate.  Most travel less than 500km to find a suitable cave or abandoned mine, where they remain for six months or more, surviving solely on stored fat reserves.  However, several species are long-distance migrators, travelling from as far north as Canada to the Gulf States or Mexico for the winter.  The giant-sized Straw-coloured Fruit Bat, Eidolon helvum of Africa make long migrations between East and West Africa flying at altitudes of up to 200m and at speeds of up to 30km/h.
 
Hibernation enables bats to ‘switch-off’ their body’s energy-expensive heating mechanism, thus allowing them to survive cold winters when insects (i.e. fuel reserves) are not available.  Body temperatures may even approach freezing point during hibernation.  Prior to hibernation, bats build up their fat reserves, which may account for a third of their body weight, and may have to last up to six month.  Disturbing hibernating bats may have tragic consequence because bats budget their fat reserves very precisely and undue arousal of bats from hibernation costs large amounts of energy reserves and may result in the bat waking up before winter is finished and, consequently, starving.
 
Most temperate-dwelling female bats (including certain South African species of horseshoe bats and hairy bats) have the ability to store unfertilized sperm from the male in their uterus throughout the entire hibernation period (i.e. mating occurs before hibernation).  Other species are able to delay implantation of the fertilized egg throughout winter (e.g. the long-fingered bats of South Africa) or to retard the development of the attached embryo over winter (e.g. Sundevall’s Leaf-nosed Bat of South Africa).
 
Typically, bats are very loyal to their birthplaces and hibernating sites.  Exactly how bats navigate is still a mystery.  They may use mountain ranges and other visual landmarks, as well as information passed from one generation to the next.
 
Bats are the world’s only true flying mammal and, in the case of insectivorous bats, catch most of their food on the wing.  The wings of bats are specially adapted to enable them to fly at speeds which allow insectivorous bats to catch insects.  Wing shape is also an important key to identifying bats.  Like swallows, bats that live in open areas and need to fly quickly have long, narrow, tapered wings.  Bats that live in heavily vegetated areas are designed more like butterflies.  They have short, broad wings that allow them to fly at slow speeds and make tight turns.

COURTSHIP, REPRODUCTION AND LONGEVITY

Most temperate-dwelling (and some tropical) bats mate in autumn just before entering hibernation.  Courtship is limited and males mate with as many females as possible.  After mating, they go into hibernation, the male sperm being stored in the female’s uterus.  Ovulation, followed by fertilization of the sperm, occurs in spring as females emerge from hibernation.  Pregnant females then move from hibernating sites (hibernacula) to warmer roosts where they form maternity or nursery colonies.  Births occur approximately a month and a half later.
 
The young grow rapidly, often learning to fly (while still being suckled by their mothers) within three weeks.  While they are being reared, males and non-reproductive females often segregate into separate colonies called bachelor colonies.
 
Some tropical bats engage in elaborate courtship rituals.  Male epauletted bats sing and flash large fluffs of white shoulder fur to attract mates.  Vampire bats are known to adopt orphans, unusual for any wild animal.
 
Bats are, for their size, the slowest reproducing mammals on earth. On average, mother bats rear only one young bat a year, and some do not give birth until they are two or more years old.  Bats are exceptionally long-lived, often living over 15 to 20 years; a few may survive for more than 30 years.

FEEDING AND ROOSTING BEHAVIOUR

Although 70% of bats eat insects, many tropical species feed exclusively on fruit or nectar (this includes not only Megachiropteran species but many species of Central and South American Microchiroptera).  Nectar-feeding bats have long tongues and noses which fit glove-like into the flowers on whose nectar they feed, and which they also pollinate.  While some bats catch insects with their mouths, others first scoop up the insect in their tail or wing membrane.
 
A few bats are carnivorous, hunting smaller vertebrates such as fish, frogs, mice and birds.  Species of blood-feeding vampire bats are found only in Latin America (not throughout the world as most people assume).
 
Water is drunk on the wing by skimming over water and gulping a mouthful or using their tongue as a ‘straw’.  This is similar to the way many birds drink water.
 
Bats can be found in most kinds of shelter, although they are best known for living in caves.  Colonies of 20 million bats are known from Braken Caves in Texas, USA while colonies of up to 8000 bats have been recorded in caves in the Natal Midlands.  The De Hoop Cave near Bredasdorp contains 300,000 bats.
 
Buildings resemble caves in many ways and suitable buildings and roofs are readily exploited by bats.  In the Gauteng region, a number of different bat species are regularly found roosting in roofs of buildings; these species may include the Egyptian Free-tailed Bat, Tadarida aegyptiaca, the Cape Serotine Bat, Neoromicia capensis and the African yellow bat, Scotophilus dinganii.
 
Tropical bats occupy a wider range of roost sites than temperate bats.  For example, so-called Banana Bats, Neoromicia nanus prefer the curled young leaves of bananas and wild Strelizia plants.  ‘Tent-making’ bats from South America make tent-like roosts by biting through the midribs of large leaves.  Others live in animal burrows, flowers, termite and bird nests, tree hollows, rock crevices and even in large tropical spider webs.