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bat bat (bāt) noun
Any of various nocturnal flying mammals of the order Chiroptera, having membranous wings that extend from the forelimbs to the hind limbs or tail and anatomical adaptations for echolocation, by which they navigate and hunt prey.
have bats in (one's) belfry
To behave in an eccentric, bizarre manner.
[Alteration of Middle English bakke, of Scandinavian origin.]
|Honduran white bats|
bat, the only MAMMAL (order Chiroptera) capable of true flight. Numbering between 1,000 and 2,000 species, bats range in size from less than 1 in. (2.5 cm) to 15 in. (45 cm), with a wingspan of from less than 2 in. (5 cm) to 5 ft (150 cm). The body is furry and mouselike, with the forelimbs and extensions of the skin of the back and belly modified to form wings. Bats are most abundant in the tropics, and temperate species often hibernate or migrate to warmer areas in the winter. Most species frequent crevices, caves, or buildings, and are active at night or twilight; they roost during the day, often in large numbers and usually hanging by their feet. Most bats see well but depend on echolocation to navigate in the dark. Bats are fruit-eaters (fruit, nectar, pollen) or insect-eaters (fruit, insects, small animals, and fish); one species, the South American vampire bat, feeds exclusively on the blood of living animals, chiefly mammals.
Although it may seem that hanging upside down requires great strength, it's actually a sign of weakness. Bats are the only mammals capable of sustained flight, but unfortunately for the bats, this special talent required some developmental tradeoffs.
To fly effectively, they had to lose weight, largely in their hind legs. As a result, bats' leg bones are so thin that they can't walk on them. When not in flight, bats drag their bodies along the ground in a way that keeps pressure off of their delicate limbs.
Once the bat is ready to roost for the day, it locks its claws to a toehold and hangs upside down. This shifts thebody weight off of the legs and onto stretched muscles and tendons in the body.
The morphology of the megabats (the "flying foxes") displays primate overtones. The very idea that bats of any kind could be closely related to humans and apes was quickly dismissed by most zoologists. Flying mammals--- the bats---evolved only once according to mainstream theory; later the Order Chiroptera ("hand-wings") split into the small, mainly insect-eating microbats and the large, fruit-eating megabats. It was all pretty obvious; how could such complex, specialized animals have evolved twice?
But in Science Frontiers, there is ever the "however":
"Arnd Schreiber, Doris
Erker and Klausdieter Bauer of the University of Heidelberg
have looked at the proteins in the blood serum of megabats and primates and found
enough in common to suggest a close taxonomic relationship between the two
groups. (Biological Journal of the Linnean Society, 51:359)"
An explanation might be that the similarities between the microbats and megabats represent adaptations to similar environmental niches rather than a common ancestry. (Timson, John; "Did Bats Evolve Twice in History?" _New Scientist_, p. 16, June 4, 1994.)
Does the black box labelled EVOLUTION contain a special subprogram for converting hands into membaneous wings whenever it seems profitable to do so? Or are we somehow missing a different sort of evolutionary process, perhaps something akin to the "directed evolution" suggested by some experiments with bacteria?
LACTATING MALE BATS
The scene is a Malaysian forest, where scientists are sampling canopy wildlife with nets:
"When the researchers captured a group of bats in a wide-ranging effort to survey animals that inhabit the Malaysian canopy, they were dumbfounded to see that the eight adult male Dyaks [a species of fruit bat] in the net all had visibly swollen breasts that produced milk upon being gently squeezed."
No other wild male mammals are known to give milk, although inbred domestic male goats and sheep will---rarely--- lactate. It is not known if the male bats actually nurse the young.
(Angier, Natalie; New York
Times, February 24, 1994. Cr. J. Covey. Also: Francis, Charles M.,
et al; "Lactation in Male Fruit Bats," Nature, 367:691, 1994. Fackelmann, K.A.; Science News,
In their book _Anomalies
and Curiosities_ of Medicine, G.M. Gould and W.L. Pyle record several
cases of human males lactating and even suckling infants.
puts human technology to shame
October 12, 1998
Web posted at: 10:36 p.m. EDT
WASHINGTON (AP) -- Bat sonar is so muchbetter than anything devised by human technology that the little creatures seem to enjoy rubbing it in.
"The bats were essentially turning to us and thumbing their noses," researcher James Simmons of Brown University said of tests aimed at challenging bats' sonar ability.
Simmons' experiments, reported in Monday's issue of Proceedings of the National Academy of Science, are aimed at improving the Navy's sonar to help detect mines under water.
Sonar systems send out a sound and then listen for the echo to bounce back. The time it takes to return tells how far away something is and in which direction. A major factor is the ability to differentiate between two echoes that arrive at almost the same time.
At the wavelengths under study, electronic sonar can differentiate between echoes about 12 millionths of a second apart.
With a lot of work, that can be cut
to 6 millionths to 8 millionths of a second, Simmons
"Bats do 2 to 3 (millionths of a second) relatively easily," Simmons said. "That's the part that's little distressing."
Being able to separate such sounds means the bats could tell the difference between objects just 3/10ths of a millimeter apart -- about the width of a pen line on paper.
In the experiment, the bats were
sitting on a platform in a familiar situation, he noted.
They probably don't do as well at night, chasing insects through the trees. "They seem to be fat and happy all thetime, which means they are intercepting their targets," Simmons observed. "The things they do are shocking."
To succeed in such chases, bats need
to be able to differentiate sounds 10 millionths of a second apart,
Simmons explained in a telephone
interview. "We'd have to do a lot of work to match what they're doing so
While they're still trying to determine why bats are so much better than human technology, they have begun experiments to record bats' brain cell activity as they process sounds.
And Simmons is working on tweaking naval sonars, both in listening for return sounds and in processing that information, to make them a bit more like bats. Dolphins also use sonar, and some have been trained by the Navy to help find mines. But Simmons said it isn't practical to do experiments on dolphins. Working with bats, on the other hand, he hopes to learn ways to improve both underwater sonar and airborne radar.
In Simmons' experiments, the bats are trained to differentiate sounds with large gaps between them, getting a reward of mealworms for each correct decision. Then the timing of the sounds is shortened to test the bats' response. "They cooperate in these experiments. ... They perform very fast," Simmons said. In an experiment, the bat makes its decision about the sound and then runs forward to get the mealworm. "They don't fly off; they just sit there and go right to it," he said.
Working with Simmons on the project were Michael Ferragamo, now at Gustavus Adolphus College, and CynthiaMoss, now at the University of Maryland.