BATS IN RELATION TO GUANO AND INSECTS 7 



and other important ingredients and has a commerical value in 

 some cases, as shown by chemical analysis, of $30 to $40 a ton. 3 



The rate of accumulation of guano varies greatly in different 

 places, being slight in the caves where the bats merely spend the 

 winters, but much more rapid where they live in great numbers all 

 the year, or through the period of summer activity. In the Cibolo 

 Creek Cave, north of San Antonio. Tex., on March 5. 1924. about 

 an inch of fresh deposit was found on the floor where the guano 

 had been removed during the winter. The bats had been active only 

 a short time, and insect life had but recently become common. 

 From this not very extensive cave there are taken out each year 

 about 60 or 70 tons of guano, said to bring $30 a ton. 



The Cibolo Creek Cave consists of a great tunnel sloping gently 

 downward for 200 or 300 yards through the limestone formation 

 toward the creek valley below, and widening out at the lower part 

 in a great room some 75 feet high and 150 feet wide. Here the 

 bats gather in vast numbers, possibly by millions, hanging to the 

 high arched roof, and rain down their little pellets over the entire 

 floor of the cave throughout their season of activity. 



The bat roo.^t in this cave has not only been a source of income to 

 the owner since 1896. but also perhaps has been of importance to the 

 community in the destruction of enough insects within the nightly 

 range of the bats to maintain this enormous host. Nevertheless 

 mosquitoes are said to be troublesome at times in the vicinity of 

 the cave, and no scarcity of any kind of insect has been noticed by the 

 residents. 



In another cave on the Frio EiVer. not far from Uvalde. Tex., 

 about the same quantity of guano had been taken out for many 

 years, until a fire in the guano drove out the bats and for the time 

 ended the deposition. Other caves in the region west of San 

 Antonio yield a somewhat smaller output of guano, and many in 

 western Texas and southern Xew Mexico and Arizona have yielded 

 it in commercial quantities. 



In the great Carlsbad Cavern of southeastern Xew Mexico the 

 quantity of guano removed during the 20 years from 1901 to 1921 is 

 estimated roughly at 100,000 tons. This was the accumulation of 

 hundreds or perhaps thousands of years, but as vast numbers of bats 

 congregate here in fall to use the cave largely as a wintering place 

 and as many leave again in spring for lower country and a better 

 food supply, the guano accumulation is relatively slow, apparently 

 not more than 1 inch a year. Many years must elapse before the 

 deposit can again become of commercial value. 



ARTIFICIAL ROOSTS FOR BATS 



Interesting experiments in building roost.- for the purpose of 

 colonizing L r uano-producing bats {Tadanda mexicana) have been 

 carried on for many years by C. A. R. Campbell, of San Antonio. 

 Tex. An excellent description of one of these buildings (tig. 3) 

 at Lake Mitchell is given by Doctor Howard, 4 from careful notes 



z Gile and Carroro, op. fit. 



4 Howard, L. O., op. cit., pp. 1792-1703. 



