I. LIFE PROCESSES 



ous tension, when prolonged, indirectly affects the reproduc- 

 tive organs which are particularly responsive to disturbances 

 of the nervous system. After a time most wild animals be- 

 come accustomed to life in- captivity and they then lose their 

 fear of man to a great extent. With the lessening of nervous 

 tension body organs function more normally. Breeding then 

 takes place at a normal rate, or it is increased in many cases, 

 presumably by the abundant and adequate food that the ani- 

 mals receive and also by the protection from enemies which 

 enables the individuals to live out the normal span of repro- 

 ductive life. 



TABLE 8 

 Showing sterility in different generations of captive gray rats 



GENERATION 



Or BREEDING 



FEMALES 



TOTAL MM HKK 

 FEMALES REARED 



I'KR I K.ST 

 RTKRII.1TY 



70.00 



30.09 



18.52 



10.71 



11.54 



11.11 



9.43 



5.88 



lvf.4 



19.49 



Data given in table 8 show the total number of females 

 reared, the number that did not breed, and the percental 

 sterility in each of the nine generations of captive Grays. 



As shown in table 8, the sterility in females of tin- first 

 generation born in captivity was 37.29 per cent, only about 

 half of that (70.00 per cent) in wild females. This percentage 

 is too high, if one takes into consideration the fact that tiv 

 of the females of the first generation escaped from the colony 

 and were not recaptured. These li\v tVniah-s ranged in age 

 from seven to thirteen months at the time of their escape. 



