COMPONENTS OF THE HERD 
The census of the seal herd might logically be arranged in 
two primary divisions, male and female, further subdivided into age 
classes from 0 to 30 years. However, on the Pribilofs the séals group 
themselves into several natural categories according to the social 
structure of the breeding ground (fig. 3). During many years of commercial 
sealing a terminology for these categories has developed. The terms~~bull, 
bachelor, pup, cow, and yearling--have been borrowed from a variety of 
zoological sources. Since they are well established in the records of the 
sealing industry, they are used in the present study. In a final census of 
the herd (page 37) an additional breakdown by age and sex classes is 
attempted. In the present discussion the herd components are treated 
from known to unknown, the bulls (easily counted) first and the yearlings 
(estimated) last. 

Figure 3. Social structure of the breeding ground. Tolstoli 
rookery and hauling ground. In foreground are breeding seals and pups; 
beyond the breeding area, the idle bulls are massed. Males nearest the 
rookery are generally the most virile and alert; they await an oppor- 
tunity to charge into the breeding area to forcefully displace an 
exhausted harem master. In the distance are two groups of bachelors, 
2 to 5 years old; from similar groups the commercial kill is taken. 
Photo taken 15 July during annual count of harem bulls at height of 
breeding season. (KWK 51 653) | 
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