With gargoyle faces, night-time habits and a reputation rooted in fear and folklore, bats linger in our collective conscious as beastly creatures of darkness. But contrary to their "bad rep", bats are not only largely harmless, they are beneficial to humans and very important to the ecosystem.
Some tropical species, like flying foxes, can weigh as much as two pounds, but most bats are very small animals, often weighing less than half an ounce, leading to the characterization of them as "flying mice". But bats, of course, aren't mice at all. All bats belong to the mammalian order Chiroptera, meaning "hand-wing", just as all rodents belong to Order Rodentia. And different bat species are as varied from each other as a beaver is from a pine squirrel.
Bat fossils date back 60 million years, to the time of dinosaurs, and the bats of today don't look a great deal different from their ancient ancestors. Bats are a successful animal group, in fact one fourth of mammal species worldwide are bats. These flying mammals were once extremely abundant, perhaps filling the sky as passenger pigeons did in the last century. But loss of habitat, persecution by humans, pesticide poisoning and other impacts from human activity have affected bat numbers tremendously. Almost 40% of bat species in America are endangered, making bats North America's most endangered mammal group. Bats are extremely slow-reproducing—most females bear only one young per year—thus bats are very vulnerable to extinction. Perhaps the most graphic example of the downward spiral of bat populations lies with the world-famous Brazilian free-tailed bats of Carlsbad Caverns National Park in New Mexico. Once estimated at eight to nine million, a mere 250,000-350,000 bats now inhabit the caves, a decline of at least 96%.
Bats have not been studied as closely as many mammals and much of their biology remains a mystery, perpetuating a fear of bats rooted in a lack of under-standing. The traits and habits bats have evolved to "earn their living" in the natural world make them very different from many mammals. Their most notable skill is the ability to fly. Bats are the only mammals so gifted (flying squirrels actually glide), and they have many physical adaptations for flight. A bat's wing is formed from an elongated forearm and four elongated fingers with a translucent membrane of skin stretched between them. The pelvis is weak and the hind legs are rotated so that the knees point out and back. The structure of the bat's pelvis doesn't allow it to sit upright, thus all bats roost hanging upside down. If a bat should land on the ground, it lies flat or crawls around crab-like.
People have long watched bats maneuver in the night sky as if blessed with otherworldly powers. Not until the 1930s did scientists begin to realize bats' magic abilities weren't so much supernatural as supersensory. Using high-pitched squeaks beyond the limits of human hearing, bats navigate and locate prey in the dark by interpreting the echoes produced when their calls bounce off objects, a technique called echolocation. Humans hear sounds at frequencies up to 20,000 cycles per second; bats hear up to about 200,000 cps. Even if humans could hear in that range, the idea of locating a creature as tiny as a mosquito strictly by the sound which bounces off its body hints of science fiction. But bats can discern a faint echo at an interval of as little as 1/1000th of a second. Flying with their mouths open, bats emit a constant stream of cries. As the animal hones in on prey, the calls become more frequent -zot, zot, zot, zzzt. High frequency sounds work better than low frequency because they can be "beamed" 
like a searchlight, producing sharper echo-images. Even so, the echoes are extremely faint, perhaps only 1/2000th of the emitted call. Thus, bats are basically shouting as loud as they can. Their cries have been measured at 100 decibels; by comparison, a jackhammer operates at a loudness of about 90 decibels.
Some moths have evolved defenses against echolocating bats; the moths recognize the bats ultrasonic calls and begin evasive maneuvers. A study found damage from corn earworm moths was reduced by 50% just by playing fake echolocation calls over a test plot. Western spotted bats do the moths one better, using lower-frequency echolocation pulses to hunt moths tuned to higher-pitched sounds.
Bats use other hunting tools as well as echolocation. Big-eared bats listen for the footsteps and chewing sounds of feeding caterpillars and swoop down to pluck the insects off of vegetation. The vision of California leaf-nosed bats is equal to the best night vision scopes, allowing them to see insects feeding on vegetation. Stop-action photography reveals how bats corral elusive prey by cupping their wings and tail membranes to scoop insects towards their mouths.
Next: Bats Are The Good Guys, Part Two
(The information contained in this issue of Colorado's Wildlife Company was accurate at the time of original publication. Situations and circumstances described, staff positions, contact information, and dates of some events may have changed in the interim. Present knowledge and understanding of biological and behavioral facts and information may also be different, now, than presented here.)