THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 207 



Little geographical segregation of deserted juveniles had ap- 

 parently occurred at the time tagging was done. Therefore, this 

 class of animals contributes the best indication of sex ratio among 

 sea otters up to approximately 1 year of age. Among 117 juveniles 

 that were captured and marked, 58 males, 58 females, and 1 of 

 unknown sex were recorded (table 39, section on Home Range). 

 This evidence suggests that the sex ratio is approximately 1 : 1 dur- 

 ing the juvenile period. 



ADULT SEX RATIO 



The areas in which females predominated were the most accessi- 

 ble to hunters. Also, these areas are more extensive than the 

 locations frequented by males (see Segergation of Sexes). Prima- 

 rily for these reasons the sex ratio of animals taken during 

 cropping operations in 1962 and 1963 were biased in favor of 

 females. The take consisted of 67 percent females and 33 percent 

 males (table 42). In the section on mortality it was shown that 

 the sex ratio among juveniles found dead on beaches during the 

 late-winter to early-spring period of stress was 58 percent males : 

 42 percent females. These data suggest that among surviving 

 adults, females outnumber males. The percent by which females 

 predominate among adults, however, cannot be derived from the 

 available data. The difference between the number of males and 

 females taken during killing operations is a result of sexual segre- 

 gation and is too great to be explained by the apparent difference 

 in male and female mortality among juveniles. 



Until further studies are conducted, it may be concluded that 

 a nearly equal number of males and females are conceived and 

 that the sex ratio remains approximately 1:1 until juveniles are 

 deserted by their mothers. At this time, more males than females 

 die of natural causes. Thus, among adults, females probably pre- 

 dominate over males. Harvesting operations tend to confirm this 

 but more data are needed. 



Table 42. — Sex ratio of sea otters killed at Amchitka Island during experi- 

 mental harvests 



[Ratio, males to females, 1:2] 



Males Females 



Total 



Date Number Percent Number Percent number 



Jan.-Mar. 1962 43 28 111 72 154 



Oct. 1962 6 25 18 75 24 



Mar.-Apr. 1963 109 36 194 64 808 



Total... 158 33 323 67 481 



