Bats
Webpages concerning "Bats"
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Wikipedia-Article "Bats"
- For other uses, see Bat (disambiguation).
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Antrozoidae |
Bats are flying mammals in the Chiroptera order with forelimbs developed as wings. Other mammals, such as flying squirrels or gliding phalangers, can glide limited distances, but only bats are capable of true flight. The name Chiroptera can be translated from the Greek term for Hand Wing, as the structure of the open wing is very similar to an outspread human hand, with a membrane (patagium) between the fingers that also stretches between hand and body.
Though the vast majority of bats (appr. 70%) are insectivorous, a significant number from both suborders, Megachiroptera and Microchiroptera (see below), feed on fruits and their juices. Three bat species eat blood but some prey on vertebrates. These bats include the Leaf-nosed bats (Phyllostomidae) of Central and South America, and the allied family Noctilionidae (Bulldog bats) that feed on fish.The Ghost Bat of Australia is one example of a carnivorous bat that even feeds on other bats. Some of the smaller species are important pollinators of some tropical flowers. Indeed, many tropical plants are now found to be totally dependent on them, not just as pollinators, but eating the resulting fruits and so spreading their seeds. This role explains environmental concerns when an exotic bat is introduced in a new setting. Tenerife provides a recent and particularly interesting example here, given the island's unique flora and fauna (much of it vestiges of the ancient continent of Gondwana). In this case, the exotic bat threatening native species is the Egyptian Bat (Roussettus aegyptiacus) 1.
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Classification
Though sometimes called "flying rodents" or "flying mice," these terms are erroneous, as bats are neither mice nor rodents.
There are two suborders of bats:
- Megachiroptera (megabats or fruit bats)
- Microchiroptera (microbats, echolocating bats or insectivorous bats)
Megabats eat fruit, nectar or pollen while microbats eat insects, blood (small quantities of blood of animals), small mammals, and fish, relying on echolocation for navigation and finding prey.
There is controversial but well-supported evidence that Megachiroptera evolved flight separately from Microchiroptera; if so, the Microchiroptera would have uncertain affinities. When adaptations to flight are discounted in a cladistic analysis, the Megachiroptera are allied to the primates by anatomical features that are not shared with Microchiroptera. Some genetic evidence, however, has pointed to the common ancestry of Megachiroptera and at least some Microchiroptera. Other genetic evidence points to Chiroptera diphyly microbat polyphyly. Most studies of eutherian relationships have attempted to avoid this issue by assuming monophyly of Chiroptera.
Little is known 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, such as Icaronycteris, Archaeonycteris, Palaeochiropteryx and Hassianycteris, are from the early Eocene (about 50 million years ago), but they were already very similar to modern microbats. Archaeopteropus, formerly classified as the earliest known Megachiropteran, is now classified as a Microchiropteran.
Bats are usually grouped with the tree shrews (Scandentia), colugos (Dermoptera), and the primates in superorder Archonta because of the similarities between Megachiroptera and these mammals.
- ORDER CHIROPTERA
- Suborder Megachiroptera (megabats)
- Suborder Microchiroptera (microbats)
- Superfamily Emballonuroidea
- Superfamily Rhinopomatoidea
- Superfamily Rhinolophoidea
- Superfamily Vespertilionoidea
- Superfamily Molossoidea
- Superfamily Nataloidea
- Superfamily Noctilionoidea
- Noctilionidae (Bulldog bats or Fisherman bats)
- Mystacinidae (New Zealand short-tailed bats)
- Mormoopidae (Ghost-faced or Moustached bats)
- Phyllostomidae (Leaf-nosed bats) This family contains (among others) the Vampire bats
Most microbats are active at night or at twilight, so the eyes of most species of microbats are poorly developed. Their senses of smell and hearing, however, are excellent. By emitting high-pitched sounds and listening to the echoes, the microbats locate prey and other nearby objects. This is the process of echolocation, a skill they share with dolphins and whales.
The teeth of microbats resemble those of the insectivores. They are very sharp in order to bite through the chitin armour 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 a bat are much more flexible than those of other mammals. One reason is that the cartilage in their fingers lacks calcium and other minerals nearer the tips, increasing their ability to bend without splintering. The cross section of the finger bone is also flattened instead of circular as is the bone in a human finger, making it even more flexible. The skin on their wing membranes is much more elastic and can stretch much more than what is usually seen among mammals.
Because their wings are much thinner than those of of birds, bats can maneuver more quickly and more precisely than birds.
Reproduction
Mother bats usually have only one offspring per year. A baby bat is referred to as a pup. 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. It would be difficult for an adult bat to carry more than one young, but normally only one young is born. 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. Two mammary glands are situated between the chest and the shoulders. 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 after 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.
Habits and Behavior
Bats vary in social structure, with some bats leading a solitary life and others living in caves colonized by more than a million bats.
The fission-fusion social structure is seen among several species of bats. The fusion part is all the individuals in a roosting area. The fission part is the breaking apart and mixing of subgroups by switching roosts with bats, ending up with bats in different trees and often with different roostmates.
Studies also show that bats make all kinds of sounds to communicate with each other. Scientists in the field have listened to bats and have been able to identify some sounds with some behavior bats will make right after the sounds are made.
Enemies
Small bats are sometimes preyed upon by owls and falcons. Generally there are few animals able to hunt a bat. In Asia there is a bird, the bat hawk, which specializes in hunting bats. The domestic cat is a regular predator in urban areas; they may catch bats as they enter or leave a roost, or on the ground. Bats will land on the ground for feeding, in bad weather, or due to accidents while learning to fly.
The worst enemies are parasites. The membranes with all their blood vessels are ideal food sources for fleas, ticks and mites. Some groups of insects suck exclusively bat blood, e.g. the bat fly. In their caves the bats hang close together, so it is easy for the parasites to infect new hosts.
The most destructive enemy of bats is probably humans, who fear the harmless animal either because of superstition or fear of rabies. Destruction of bat habitat and elimination of their food source (primarily insects) negatively affects the species.
Vector for rabies
The following advice is only relevant to areas with endemic rabies.
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 most bats do not have rabies, those that do may be clumsy, disoriented, and unable to fly, which makes it more likely that they will come into contact with humans. 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. If a bat is found in living quarters near a child, mentally handicapped person, intoxicated person, sleeping person, or pet, the person or pet should receive immediate medical attention for rabies. Bats have very small teeth and can bite a sleeping person without necessarily being felt.
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 the 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 guano, bats should be excluded from inhabited parts of houses. For full detailed information on all aspects of bat management, including how to capture a bat, what to do in case of exposure, and how to bat-proof a house humanely, see the Centers for Disease Control's website on bats and rabies. In certain countries, such as the UK, 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 as harmless. Larger bats can give a nasty bite. Treat them with the respect due to any wild animal.
Cultural aspects
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 the Kwakiutl and Arabs.
In Western Culture, the bat is often a symbol of the night and its forboding nature. The bat is a primary animal associated with fictional characters of the night such as 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 Oppell, who created a best selling series of novels, beginning with Silverwing, which feature bats as the central heroic figures much in a similar manner as the classic novel Watership Down did for rabbits. An old wives' tale has it that bats will entangle themselves in people's hair. A likely root to this myth 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.
Austin, Texas is the summer home to North America's largest urban bat colony, an estimated 1,500,000 Mexican free-tailed bats, who eat an estimated 10,000 to 30,000 pounds of insects each night and attract 100,000 tourists each year.
References
- Greenhall, Arthur H. 1961. Bats in Agriculture. A Ministry of Agriculture Publication. Trinidad and Tobago.
- Nowak, Ronald M. 1994. " Walker's BATS of the World". The John Hopikins University Press, Baltimore and London.
- John D. Pettigrew's summary on Flying Primate Hypothesis
See also
External links
- United States Bat Rescue
- Bat Conservation International website
- Bat World Sanctuary
- Texas Parks and Wildlife Bat Page
- University of Michigan Museum of Zoology
- Tree of Life
- Flying Fur
- Seek My Bowl on bat as symbol.
- Bats make up 20% of mammals
- The Bat Conservation Trust
- Adopt-a-Bat
- Organization for Bat Conservation
- Illustrated Identification key to the (micro)bats of Europe (see "Recent publications")
| Mammals |
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Marsupialia: Didelphimorphia | Paucituberculata | Microbiotheria | Dasyuromorphia | Peramelemorphia | Notoryctemorphia | Diprotodontia |