4 BULLETIN 1395, U. S. DEPARTMENT OF AGRICULTURE 



Texas, and New Mexico. In Porto Rico 110 caves have been listed, 

 containing from 12 to 3.144 tons of guano, and many others exam- 

 ined containing little or no guano. 3 In no case is the .species or 

 genus of bat responsible for the guano deposits mentioned, but in 

 every case the records of deposits lie within the range of some 

 species of the genus Tadarida. This does not mean that these are 

 the only bats producing guano of high fertilizer value in commercial 

 quantities, but so far as known they are the only bats in America 

 sufficiently gregarious to do so. 



BAT CAVES 



The most strikingly characteristic habit of Mexican free-tailed 

 bats is that of gathering in large colonies in caves and buildings. 

 This habit renders them valuable through the production of large 

 quantities of guano, and possibly through the consumption of many 

 kinds of injurious insects. They are especially numerous in south- 

 ern Texas and New Mexico, where for centuries they must have 

 occupied great numbers of the natural caves which afford ideal 

 refuges for them. Many of the larger caves contain hundreds of 

 thousands during the whole or a part of each year. 



Some of the caves, such as the great Carlsbad Cavern, N. Mex., 

 are mainly wintering places, where the bats hang in fall, and sleep 

 until the 1 warm days of spring call them out again to seek the most 

 satisfactory feeding grounds, and to feast on their winged prey. 

 Where the caves are in proximity to an abundance of insect life the 

 bats remain throughout the summer, occupying the caves as roosting 

 places during the day, and swarming out over the country in search 

 of food at night. One such cave is about 19 miles north of San 

 Antonio, Tex., on Cibolo Creek; and, although not very extensive, 

 it annually yields a large quantity of guano. This and other caves 

 west of San Antonio are occupied by great numbers of these bats, 

 as are still others in western Texas and across southern Xew Mexico. 

 Apparently this whole cave region is stocked with bats to its carry- 

 ing capacity, besides providing wintering shelter for those of out- 

 lying areas, where no caves occur. 



GENERAL HABITS OF THE SPECIES 



Like most other bats, the Mexican free-tailed bats are almost 

 entirely nocturnal in habits and apparently continue active through- 

 out the night. Emerging from their roosting places after sunset, 

 they seek their feeding grounds for pursuit of the flying insects 

 which are their food. They are strong, rapid flyers and will even 

 breasl a still breeze, but in feeding they keep mainly in the vicinity 

 of trees, buildings, or cliffs, where the air is teeming with insect life. 

 Their progress while feeding is in quick and erratic zigzags as the 

 insects are rapidly snapped tip and devoured without a moment's 

 pause. 



During summer evenings at San Antonio, Tex., soon after sun- 

 down it is common to see great numbers of these bats flying over 



»Gile, P. I,., and .1. 0. Carrero, " Th<> Bat Guanos of Porto RLoo and Their Fertilizing 

 Value": Bui. No. 25, Portp Rico Agr. Exp. Sta., pp. G6, 1918. 



