Biology Reference
In-Depth Information
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 objects, their “echoes” re-
turn to the bat, which, with its incredible hearing, identifies and locates these objects with uncanny pre-
cision. This “radar” system is so amazingly sophisticated that scientists still lack anything approaching
a full understanding of it.
The eighteenth-century Italian biologist Lazzaro Spallanzani was the first to postulate that bats could
navigate in total darkness through a mysterious sense connected to their hearing. His views were gen-
erally ridiculed until the 1930s, however, when Donald R. Griffin, a Harvard University bat biologist
and researcher, confirmed Spallanzani's beliefs and identified the mysterious sense as echolocation.
However, even though scientists are still learning about echolocation, they do know that it depends
on two components, one physical and the other biological. In the physical component, a bat emits high-
pitched sound waves. When these waves strike an object, they “echo”—that is, bounce back to be re-
ceived by the bat's incredibly sensitive ears. Then the biological component of echolocation takes over,
as the bat translates this information with astonishing accuracy and rapidity into an aural picture of its
surroundings.
Not only is each nearby object placed precisely in spatial terms, but its size and form are also evident
to the bat. Thus a bat can instantly determine whether its system has locked on a human, a branch, a
tiny mosquito, or a larger, slow-moving moth. Moreover, it is constantly assimilating this stream of in-
formation not for one object, but for all of the many objects around it. So remarkably rapid and precise
is this echolocation system that a bat can fly through a maze of wires strung throughout a totally dark
room!
