118 ANIMAL LIFE OF CARLSBAD CAVERN 



scattered about. Most of these bones are in half- 

 hidden corners or little niches in the wall, as if the bats 

 had become unable to rise from the floor from weakness, 

 and had crawled into some corner to die. Many of the 

 skulls show the worn-out teeth of old age, or young bats 

 just able to fly, but others in the prime of life may have 

 become poor and weak from lack of proper food and 

 adverse weather conditions, and so were unable to make 

 the steep aerial climb out of the shafts of the cave. In 

 other caves the same conditions have been noted, large 

 numbers of dead bats being gathered in certain places 

 in the far corners of the cave bottom, where they have 

 been reduced to skeletons and may have been preserved 

 for a long time. A few mummies of bats with matted 

 fur still clinging to crumbling skin were also found with 

 the bare bones or scattered here and there over the 

 cave floors. 



If the natural life of a bat were ten years, from a 

 colony of a million there would be about a hundred 

 thousand die of old age each year, so it is not strange 

 that thousands of skeletons are to be found in places 

 where there is nothing to destroy the animals. 



The free-tailed, like most other species of bats, has 

 but one young a year, born in May or June. Mating 

 probably takes place in July or August, but the repro- 

 ductive process is retarded during the period of hiber- 

 nation. The first bats taken at the cave in March 

 were all males, but females first taken as they came out 

 on April 24 contained embryos seven millimeters in 

 diameter, or about the size of a number 6 buckshot. 

 On May 9, the egg-like embryonic sack was 11 mm. in 



