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Show 326 THE NATIONAL GEOGRAPHIC MAGAZINE Photograph by Vernon Bailey A MOTHER RED BAT AND HER FAMILY OF FOUR YOUNG This mother bat was brought into the National Museum just as she was found hanging to a twig in a maple tree. Each of her four young was clinging to a nipple with its mouth and to the mother's fur with its twelve hooked claws. The four young weighed 12.7 grams, while the mother weighed only 11 grams, so they were a little more than a quarter grown. They showed no inclination to let go, and it must be inferred that the mother carries them while flying in pursuit of insect prey until they are old enough to hang up in the tree and wait for her return, or to fly and catch their own food (see text, page 330). quent inactivity of the bats, and the resulting slight deposits of guano. I could not catch sufficient insects to satisfy the appetites of my captive bats, and thus test the rate of deposit. The bats evidently could not catch enough insects during the cool nights to fill their stomachs, which on the return to the cave in the early morning were not more than half full. Stomachs of bats coming out in the evening usually were empty. Under the densest part of the bat colony, on April 29, a paper 20 by 30 inches was spread to catch the droppings. In 44 hours it caught 1,145 pellets, which weighed at first 5 grams and w h e n air-dried 3.7 grams. These did not more than half cover the surface of the paper, so that a single l a y e r of droppings about 2 millimeters thick would have required over 2,000 pellets and about 4 days of time. The fact that in the three years since any guano has been removed from the cave there have accumulated no deposits more than three inches in depth would indicate a very slow rate of deposit, even where the bats are very numerous. One inch a year of fresh pellets would certainly s h r i n k to half an inch when disintegrated to dust and packed and settled into the solid mass of the old, deep guano, rich in nitrogen, phosphoric acid, potash, and other valuable elements of plant growth. Even under a large colony of bats, it would seem that 50 feet of guano might well represent the food refuse of more than 1,000 years. But for most of the bat colony this cave is a winter resort rather than a summer home. In other caves farther south, where the bats live both summer and winter, the rate of deposit is much more rapid. In a smaller cave near San Antonio, Texas, about 60 tons of bat guano have been taken out annually for 29 con- |