Owls Aren't Wise and Bats Aren't Blind by Warner Shedd Page B

Most bats are, after all, very small, fragile creatures with delicate bones, which doesn’t make them the best of subjects for fossil preservation. Also, most of the very early bats were in tropical regions, where decay takes place with astonishing rapidity and there’s not much of the sedimentation needed to preserve fossils.
    There is evidence of evolutionary processes at work in these earliest bat fossils, however.
Icaronycteris
and
Archeonycteris
appear to be somewhat more primitive in ear and throat structures than
Hassianycteris
and
Paleochiropteryx.
    Whatever the evolutionary path, bats developed a unique wing structure. Whereas birds and pterosaurs (or pterodactyls, if you wish) evolved with wings supported by the bones of the arm and a single finger, a bat’s wing is supported by the arm and
four
greatly elongated fingers. Thus the order to which bats—and only bats—belong is Chiroptera, Greek for “hand-wing.”
    The bat’s fifth finger, or “thumb,” incidentally, far from being elongated in the manner of its other digits, is a small hook used for climbing or walking. Yes, even though flight is their normal mode of locomotion, bats actually do climb such things as cave walls and trees, and even walk along the ground on occasion when seeking food. Neither are bats helpless in the water, for competent observers have even observed them swimming.
    Flexible, yet strong for their extremely light weight, the elongated finger bones form a perfect support system for the bat’s wings. The actual wings consist of a wonderful double membrane of skin, similar to very thin, pliable leather. These wings not only cover the elongated finger bones, but also continue rearward until they actually attach to the tiny hind legs. Another section of this membrane connects one hind foot to the other; in most species, this rear section of membrane extends back to the tip of the tail. In so-called freetail bats, however, the slender tail itself projects well beyond the tail membrane.
    This design of a bat’s wing can be compared to that of an airplane. Just as an airplane wing has a thin skin of aluminum on the top and bottom, covering a network of ribs and struts to lend rigidity, bats have a skin covering over the top and bottom of their wing bones, with blood vessels and nerves in the space between.
    The result of all this is that bats have a very large airfoil in comparison to their weight. In terms of human technology, this makes them somewhat analogous to the old-fashioned biplanes. A biplane’s very large ratio of wing surface to weight made it slow but highly maneuverable. In the same manner, bats are fairly slow fliers compared with many birds, but they have incredible maneuverability.
    Have you ever watched
—really
watched—bats in flight? Few people have; most who view bats from time to time either fear and loathe them or at best give them only cursory attention. This is unfortunate, because bats are truly amazing fliers! My wife and I often sit on our patio at dusk to watch the “bat show.” The land slopes away steeply below our patio, so that bats at eye level and above are silhouetted against the evening sky. Thus we’re able to enjoy the well-nigh incredible maneuvers which these little fliers make in pursuit of their prey.
    This leads us to the method that most of our native bats use while hunting. Although the expression “blind as a bat” is a common one, it’s at least as inaccurate as it is common. Different species of bat vary somewhat in the quality of their vision, but no bats are blind, and most actually see quite well.
    However, when flying in the dark while searching for tiny insects, even excellent night vision has serious limitations. Instead, bats rely on a most remarkable system, similar to radar or sonar, known as
echolocation.
To describe this system in its most basic terms, a bat in flight emits highfrequency sound pulses, above the range of human hearing. When these pulses strike nearby