252 



NORTH AMERICAN FAUNA 74 



• Of the 20,100 animals in female herds, the females alone were 26% 

 immature (under 6 years) and 74% adults (Krylov 1968). But there must have 

 been at least one-third as many immature males (under 6 years), as immature 

 females. Hence, the overall proportions were about 8% (1,605) males under 

 6 years old, 24% (4,825) females under 6 years old, and 68% (13,670) adult 

 females. 



To these approximations must be added the walruses that were in Alaskan 

 waters in late summer. Herd numbers and composition were not as well docu- 

 mented there, but it is clear that at least 3,000 males were using Bristol Bay 

 (V. N. Crosby, personal communication), and it is probable that mixed herds of 

 as many animals were in the eastern Chukchi Sea. From photographs of about 

 half of the males on Round Island in 1958, I estimated their age composition as 

 8 % (240) under 6 years old, 11 % (330) 6 to 9 years old, 31 % (930) 10 to 14 years 

 old, and 50% (1,500) 15 years and older. These proportions are different from 

 those given by Gol'tsev (1968) for the Rudder Spit herd. They have been 

 confirmed, however, by Miller (1976: Table 5), who classified more than 3,000 

 males at Round Island in 1972-73 as 20% "small," 39% "medium," and 41 % of 

 "large" size. Although precise ages cannot be assigned to these size classes. 

 Miller's "small" animals probably were less than 10 years old; the 

 "medium"-sized individuals probably were between 10 and 15 years old; and the 

 "large" individuals would have been mature adults more than 15 years old (cf . 

 Miller 1975fl: Figs. 2, 7, 8-11, 14). 



I assume that the herds in the eastern Chukchi Sea were all of the mixed type 

 and that their composition was comparable to that of mixed herds in Soviet 

 waters, about 13% (390) males under 6 years old, 7% (210) males 6 to 9 years 

 old, 14% (420) males 10 to 14 years old, 7% (210) males over 14 years old, 11 % 

 (330) females under 6 years old, and 48% (1,440) females 6 years and older. 



On summing these estimates (Table 43), I infer that the population in 1960 

 was made up of about equal numbers of males and females. Immature males (up 

 to 9 years) made up 21%, and immature females (up to 5 years) were 12%. 

 Males of breeding age (10 years and older) made up about 29%; mature males 

 15 years and older were about 14% , and females of breeding age (6 years and 

 older) made up about 38% of the population. 



This reconstruction obviously is not accurate, for the number of males in the 

 10- to 14-year class should be smaller than that in the 0- to 5-year class. Also, one 

 would expect the males and females in the 0- to 5-year class to be about equal. 

 The somewhat smaller number of females than of males, overall, is consistent 

 with Burns' (1965) estimation that the harvests before 1960 removed more 

 females than males from the population. 



Population in 1972 



Proportional counts of walruses in their wintering areas in the Bering Sea were 

 obtained in the early 1970's in conjunction with several aerial and shipboard 

 surveys (F. H. Fay, unpublished data). By applying these proportions to 

 Kenyon's (1972) median estimate of 123,640 animals in the population, the 

 composition of the population in 1972 can be inferred. 



Kenyon (1972) recognized from the results of his 1972 survey that the animals 

 were unevenly distributed in the pack ice, being concentrated in the vicinity of 



