National Geographic : 1925 Sep
BATS OF THE CARLSBAD CAVERN By VERNON BAILEY BIOLOGIST, BIOLOGICAL SURVEY, U. S. DEPARTMENT OF AGRICULTURE BATS-celebrated in art, story, and drama as emblems of evil and darkness, associated with Satan and the infernal regions, supposed to be teeming with vermin and prone to en tangling alliances with ladies' hair-are one of our least-known and most-maligned groups of mammals; least known because they are highly nocturnal and rarely seen except in semidarkness, and because in daytime they hide away in dark places, which are rarely accessible except to pry ing naturalists. Many intelligent people ask whether they are reptiles or birds, and my boy scouts always want to know whether I mean leatherwing bats or bull bats.* So strong are superstition and imagina tion that constant reiteration of some of the well-known facts regarding the habits of bats seems necessary to an appreciation of their great value to man. Bats are mammals of a very old and highly specialized group. They were hang ing upside down in caves long before the first cave man came to join them; and. while they may not have acquired great mental powers, they have developed spe cial senses of which man has little knowl edge or appreciation. They have pro gressed along so many different lines that they now form one of the very large or ders or groups of the mammals of the world, represented in America by numer ous families, genera, and species. Many of the families and genera are world-wide in distribution, and in G. S. Miller's latest list of the Mammals of North America 252 species of bats are given. Still, to most people a bat is a bat, without regard to a wide range of habits and structural differences. BATS ARE CLAD IN FUR AND HAVE SHARP TEETH TO CIEW TIIEIR FOOD Although clothed in fur instead of feathers, their powers of flight are com parable to those of birds, or even superior * It seems almost unnecessary to say that "bull bats" are nighthawks, birds related to the whip poorwill. for their purposes. On their wide, elastic wings they can fly slowly or rapidly, and make the necessary short turns in air to capture their insect prey. With minute eyes and apparently short range of vision, and even with eyes cov ered, they detect and capture their prey in the air, avoid all solid objects, or even the finest wires or strings stretched in their paths, and find their way through long and intricate passages with no trace of light to guide them. Strangest of all, they wander far and wide over the country at night in search of food, and with unerring sense return at daybreak to the same place to sleep, and guided in some way unknown and in comprehensible to us, some make migra tory journeys north and south over conti nental areas and wide stretches of ocean. BATS FEED RAPIDLY AND CONSUME GREAT NUMBERS OF HARMFUL INSECTS All of the bats of America north of the Tropics are entirely insectivorous, feeding upon and controlling the abun dance of the night-flying insects, just as the birds do the daylight species. They feed rapidly and consume great numbers of insects; their stomachs are large, and after a half hour of feeding sometimes weigh a quarter as much as the whole animal. On the basis of only two full meals in a night, which may be far too low an estimate, bats would consume half their weight in insects every 24 hours. The insects eaten are not easily identi fied, as bats have good teeth and chew their food to the finest bits. The wing scales of moths and the hard particles- jaws, legs, shells, and wings-of beetles and flies form a large part of the recog nizable stomach contents, but other night flying insects are also extensively eaten. Mosquitoes, gnats, and such delicate in sects are rarely recognizable in their food, but undoubtedly form some part of it. So far as we know, the insects eaten are mainly our enemies and might, in un checked abundance, injure or destroy our forests and crops.