The Mysterious and Misconstrued World of Bats

This mysterious, frightening (to some) mammal has obtained a reputation through human history to the point that they have been a normal appearance in horror films and the subject for science fiction screenplays. But modern scientific investigation reveals the true side of this ancient flying mammal.

The bat is in categorized in the scientific order Chiroptera, which derives from the Greek words cheir (“hand”) and pteron (:wing”) because the structure of its open wing is similar to the outspread human hand with a membrane called a patagium between the fingers that stretches between hand and body. This amazing mammal, the only mammal that actually can fly in true flight has received bad publicity in ancient and modern human history.

This article was inspired by a recent scientific news story dated February 29^th, 2008 via BBC News – Bat takes flight cue from insects …

Bats use the same aerodynamic mechanism as insects to hover in one place, scientists have found. …the motion created a tiny cyclone of air known as a “leading edge vortex”. This provided enough lift force to keep the bat airborne while hovering or flying in slow motion. A joint Swedish and US team set up honey-water feeding stations in a wind tunnel then used fog, lasers and high speed cameras to study how the bats flew. … The animal uses thumbs and fingers embedded in the skin membrane of its wings like flaps on an aeroplane to alter the curve of the wing and create the lift force required to hover. Insects have thicker wings than bats and cannot control the movement to the same extent … But they are able to produce LEVs because they beat their wings very quickly. The findings could be used to improve the design of tiny aeroplanes used in surveillance. …

Wikipedia entry:

A measure of the success of bats is their estimated total of about 1,100 species of bats worldwide, accounting for about 20 percent of all mammal species. About 70 percent of bats are insectivores. Most of the rest are fructivores, with a few species being carnivorous. Bats are present throughout most of the world, including Alaska. Bats perform a vital ecological role by pollinating some flowers, and also have an important role in seed dispersal’ indeed, many tropical plants are totally dependent on bats. This role explains environmental concerns when a bat is introduced in a new setting. Tenerife provides a recent example with the introduction of the Egyptian fruit bat.
Since bats are terrestrial and light-boned, there are few fossilized remains. An early Eocene bat, Onychonycteris finneyi, was found in the 52-million-year-old Green River Formation in Wyoming (US) in 2003. The new genus was placed in a new family when it was published in Nature, February 2008. It was clearly a flier, but the well-articulated skeleton showed underdeveloped cochlea of the inner ear, which provide echolocation capabilities in all modern true bats, demonstrating at last that flight in bats was developed before echolocation. Another early Eocene fossil Icaronycteris index was unearthed in 1960.
…sometimes called “flying rodents”, “flying mice”, or even mistaken for insects and birds, bats are not, in fact, any of these things. There are two suborders of bats: Megachiroptera (megabats); Microchiroptera (microbats/echolocating bats).
Despite the name, not all megabats are larger than microbats. The major distinction between the two suborders is based on other factors:
- Microbats use echolocation, whereas megabats do not (except for Rousettus and relatives).
- Microbats lack the claw at the second toe of the forelimb.
- The ears of microbats do not form a closed ring, but the edges are separated from each other at the base of the ear.
- Microbats lack underfur; they have only guard hairs or are naked.
Megabats eat fruit, nectar or pollen while microbats eat insects, blood (small quantities of the blood of animals), small mammals, and fish. While megabats have a well-developed visual cortex and show good visual acuity, microbats rely on echolocation for navigation and finding prey. …
Genetic evidence indicates that megabats should be placed within the four major lines of microbats (Yinochiroptera), who originated during the early Eocene. The same research also seems to support the view that the microbats are the original bats while megabats evolved from them independently through parallel evolution, where most of them lost the ability to use echolocation.
There is some morphological evidence that Megachiroptera evolved flight separately from Microchiroptera. For example, the brains of megabats show a number of advanced characteristics linking these animals to primates, which have been deemed unlikely to have arisen by parallel evolution. … (see Flying primates theory). However, new evidence strongly supports the point of view that bats form a monophyletic group.[I]
Little hard evidence exists about the evolution of bats, since their small, delicate skeletons do not fossilize well. However a Late Cretaceous tooth from South America resembles that of an early Microchiropteran bat. The oldest known definite bat fossils … are from the early Eocene (52.5 million years ago), but they were already very similar to modern microbats. …
Bats are traditionally grouped with the tree shrews (Scandentia), colugos (Dermoptera), and the primates in superorder Archonta because of the similarities between Megachiroptera and these mammals. However, molecular studies have placed them as sister group to Ferungulata – a large grouping including carnivorans, pangolins, odd-toed ungulates, even-toed ungulates, and whales. …
Megabats are primarily fruit- or nectar-eating. They have probably evolved for some time in New Guinea without microbat concurrention. …
By emitting high-pitched sounds and listening to the echoes, also known as sonar, microbats locate prey and other nearby objects. This is the process of echolocation, an ability they share with dolphins and whales. …
Although the eyes of most microbat species are small and poorly developed, leading to poor visual acuity, it is incorrect to assume that they are nearly blind. Vision is used as an aid to navigation especially at long distances, beyond the range of echolocation. It has been discovered that some species are able to detect ultraviolet light. Their sense of smell and hearing are excellent.
The teeth of microbats resemble those of the insectivorans. They are very sharp in order to bite through the hardened armor of insects or the skin of fruits. While other mammals have one-way valves only in their veins to prevent the blood from flowing backwards, bats also have the same mechanism in their arteries. The finger bones of bats are much more flexible than those of other mammals. One reason is that the cartilage in their fingers lack calcium and other minerals nearer the tips, increasing their ability to bend without splintering. … The skin on their wing membranes is a lot more elastic and can stretch much more than is usually seen among mammals. Because their wings are much thinner than those of birds, bats can maneuver more quickly and more precisely than birds. The surface of their wings is also equipped with touch-sensitive receptors on small bumps called Merkel cells, found in most mammals, including humans. But these sensitive areas are different in bats as each bump has a tiny hair in the center,[II] making it even more sensitive, and allowing the bat to detect and collect information about the air flowing over its wings. An additional kind of receptor cell is found in the wing membranes of species that use their wings to catch prey. The receptor cell is sensitive to the stretching of the membrane. The cells are concentrated in areas of the membrane where insects hit the wings when the bats capture them.
One species of bat has the longest tongue of any mammal relative to its body size. This is extremely beneficial to them in terms of pollination and feeding – their long narrow tongues can reach deep down into the long cup shape of some flowers. When their tongue retracts, it coils up inside their rib cage.
Mother bats usually have only one offspring per year and they are viviparous. A baby bat is referred to as a pup.[III] Pups are usually left in the roost when they are not nursing. However, a newborn bat can cling to the fur of the mother and be transported, although they soon grow too large for this. … Bats often form nursery roosts, with many females giving birth in the same area, be it a cave, a tree hole, or a cavity in a building. Mother bats are able to find their young in huge colonies of millions of other pups. Pups have even been seen to feed on other mothers’ milk if their mother is dry. Only the mother cares for the young, and there is no continuous partnership with male bats. The ability to fly is congenital, but at birth the wings are too small to fly. Young microbats become independent at the age of 6 to 8 weeks, megabats not until they are four months old. At the age of two years, bats are sexually mature. A single bat can live over 20 years, but the bat population growth is limited by the slow birth rate.

Some interesting bits of information about bats:

- Most microbats are active at night or twilight.
- Many bats migrate, while others pass into torpor in cold weather but rouse themselves and feed when warms spells permit insect activity. Yet others retreat to caves for winter and hibernate for six months. Bats rarely fly in rain because rain interferes with their echolocation ability.

- Socially their behavior is varied among the species. Some bats have a solitary life, while others live in large colonies in caves with a population of one million or more in large caves. Bats, when they live in a colony can be found to roost in groups with certain individuals leaving one roost and going to another roosting group.

- Studies show that bats communicate with each other with various sounds. Scientists have listened to bats in the field and have been able to identify some sounds with some behavior of bats.

– About 70% of bat species are insectivorous and locate their prey by sonar. The rest mostly feed on fruit. Only three species feed on blood of mammals or feed on vertebrates, these are: leaf-nosed bat of Central America and South America, and the two bulldog bat species, which feed on fish. At least two species of bat are known to feed on other bats – the Spectral bat (American False Vampire Bat) and the Ghost Bat of Australia (endangered specie). One species, the Greater Noctule Bat, is believed to catch and eat small birds in the air.

- Stories of bats passing on infectious diseases like rabies, severe acute respiratory syndrome, Henipavirus, and some scientists suspect they also have passed on the Ebola virus. According to Wikipedia entry:

- Only 0.5% of bats carry rabies. However, of the very few cases of rabies reported in the United States every year, most are caused by bat bites. … Although one should not have an unreasonable fear of bats, one should avoid handling them or having them in one’s living space, as with any wild animal. … Bats have very small teeth and can bite a sleeping person without necessarily being felt. There is evidence that it is possible for the bat rabies virus to infect victims purely through airborne transmission, without direct physical contact of the victim with the bat itself.[IV]
If a bat is found in a house and the possibility of exposure cannot be ruled out, the bat should be sequestered and an animal control officer called immediately, so that the bat can be analyzed. This also applies if the bat is found dead. If it is certain that nobody has been exposed to the bat, it should be removed from the house. The best way to do this is to close all doors and windows to the room except one to the outside. The bat should soon leave.
Due to the risk of rabies and also due to health problems related to their fecal droppings (guano), bats should be excluded from inhabitated parts of houses. …see the Center for Disease Control’s website on bats and rabies. In certain countries, such as the United Kingdom, it is illegal to handle bats without a license. Where rabies is not endemic, as throughout most of Western Europe, small bats can be considered harmless. Larger bats can give a nasty bite. They should be treated with respect due to any wild animal.

History and cultural aspects of the bat:

The bat is sacred in Tonga and West Africa and is often considered the physical manifestation of a separable soul.
- Bats are closely associated with vampires, who are said to be able to shapeshift into bats, fog, or wolves.
- Bats are also a symbol of ghosts, death, and disease.
- Among some Native Americans, such as the Creek, Cherokee and Apache, the bat is a trickster spirit.
- Chinese lore claims the bat is a symbol of longevity and happiness, and is similarly lucky in Poland and geographical Macedonia and among Kwakiutl and Arabs.
- The bat is also a heraldic animal of the Spanish autonomous community of Valencia.
- Pre-Columbian cultures associated animals with gods and often displayed them in art. The Moche people depicted bats in their ceramics.
- In Western Culture, the bat is often a symbol of the night and its foreboding nature. The bat is a primary animal associated with fictional characters of the night, both villains like Dracula and heroes like Batman. The association of the fear of the night with the animal was treated as a literary challenge by Kenneth Oppel, who created a best selling series of novels, beginning with Silverwing, which features bats as the central heroic figures much as anthropomorphized rabbits were the central figures to the classic novel Watership Down.
- An old wives’ tale has it that bats will entangle themselves in people’s hair. One likely source of this belief is that insect-eating bats seeking prey may dive erratically toward people, who attract mosquitoes and gnats, leading the squeamish to believe that the bats are trying to get in their hair.
- In the United Kingdom all bats are protected under the Wildlife and Countryside Acts, and even disturbing a bat or its roost can be punished with a heavy fine.
- In Sarawak, Malaysia bats are protected species under the Wildlife Protection Ordinance 1998 (see Malaysian Wildlife Law). The large Naked bat (see Mammals of Borneo) and Greater Nectar bat are consumed by the local communities.
- Bats can be a tourist attraction. The Congress Avenue Bridge in Austin, Texas is the summer home to North America’s largest urban bat colony, an estimated 1,500,000 Mexican free-tailed bats, which eat an estimated 10,000 to 30,000 pounds of insects each night. An estimated 100,000 tourists per year visit the bridge at twilight to watch the bats leave the roost.
- Many people put up bat houses to attract bats just like many people put up birdhouses to attract birds. Bat houses can be made from scratch, made from kits, or bought ready made. Plans for bat houses exist on many web sites, as well as guidelines for designing a bat house. Some conservation societies are giving away free bat houses to bat enthusiasts worldwide.
- A bat house constructed in 1991 at the University of Florida campus next to Lake Alice in Gainesville has a population of over 100,000 free-tailed bats.
- In Britain, pillboxes dating from World War II have been converted to make roosts for bats. Pillboxes that are well dug-in and thick walled are naturally damp and provide a stable thermal environment that is required by bats that would otherwise hibernate in caves. With a few minor modifications, suitable pillboxes can be converted to artificial caves for bats.
- And during World War II, Bat Bombs were developed in an effort to attack the mainland of Japan, conceived by a dental surgeon Lytle S. Adams, who submitted his idea to the White House in January of 1942, researched approved by President Roosevelt. Dr. Adams was recruited to research and obtain a supply of bats for the operation. 

The plan was to release bomb-laden bats at night over Japanese industrial targets. The flying bats would disperse widely, then at dawn they would hide in buildings and shortly thereafter built-in timers would ignite the bombs, causing widespread fires and chaos. … The project was considered serious enough that Louis Fieser, the inventor of military napalm, designed 0.6 ounce (17 g.) and one ounce (28 g) incendiary devices to be carried by the bats …renamed Project X-Ray … More tests were scheduled for the summer of 1944 but the program was canceled by Fleet Admiral Ernest J. King when he heard that it would likely not be combat ready until mid-1945. By that time it was estimated that $2 million had been spent on the project. … Dr. Adams maintained that the bat bombs would have been effective without the devastating effects of the Atomic bomb. He is quoted as having said:
“Think of thousands of fires breaking out simultaneously over a circle of forty miles in diameter for every bomb dropped. Japan could have been devastated, yet with small loss of life.”[V]

Also see: Project Pigeon, another military use of animals; The Bat Bombers, Journal of the Airforce Association, October 1990, Vol. 73, No. 10.

And, as a trivia bit of information: A musical band was formed in America called the Fruit Bats in 1999 consisting of a guitarist, pianist and singer Eric Johnson, who was the band’s main songwriter. Originally formed in Chicago, they are now based in Seattle. Eric Johnson has now joined The Shins, though according to their web site, he plans to continue working with the Fruit Bats. Their first recorded/released album in 2001 was entitled Echolocation. Of course.

Sources and Further Reading:

Meet Our Animals – Egyptian Fruit Bat
Bat World – Rescue, Rehab, Release, and Sanctuary
Bats4Kids – Site designed for children, created for awareness and protection of Bats as an “endangered species” 
Bat Species – Wikipedia
Bat Roosts in Britain – Wikipedia
Bat Categories – Wikipedia
List of Australian Bats – Wikipedia
List of Fictional Bats – Wikipedia
European Bat Night – Wikipedia (popular annual event in Europe)
Bats! Why Should You Care? – Contra Costa County Office of Education, California
Defenders of Wildlife – Bats
Bats (1999 film) starring Lou Diamond Phillips
Desert USA – Bats in the Desert Southwest
Why are Bats Endangered? – k12-California

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[I] Nancy B. Simmons, Kevin L. Seymour, Jo rg Habersetzer, & Gregg F. Gunnell. “Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation”. Nature. Doi:10.1038/nature06549.

[II] Melissa Calhoun (15 December 2005). Bats Use Touch Receptors on Wings to Fly, Catch Prey, Study Finds.

[III] Baby bats under threat from wet weather, Bat Conservation Trust, 3 July 2007, retrieved 2 August 2007.

[IV] Constantine, Denny G. (April 1962). Rabies transmission by nonbite route. Public Health Reports 77 (4).

[V] Note: The book Sunwing written by Kenneth Oppel was inspired by this plan.