FUR SEALS AND OTHER LIFE, PRIBILOF ISLANDS, I914. 53 



COWS. In the absence of idle bulls, these cows must be served either by the old bulls or 

 by the 5-year-old half-bulls. It can not be said that any such cows ever have escaped 

 service, but it is plain that an absence of idle bulls would be the first condition favoring 

 its possibility. A number of idle bulls proportionate to the number of virgin cows, there- 

 fore, would be the safest guaranty that all such cows would be impregnated. 



The virgin cows do not appear on the rookeries until relatively late in the season and 

 remain on land but a short time. Apparently they come in greatest numbers at about 

 the time the regular harems are breaking up and the old bulls retiring from the breeding 

 areas. Although some of them are doubtless served by the old bulls, this is exceptional, 

 for the majority of the old bulls leave each season at approximately the same time 

 whether idle bulls are present or not. This leaves the young half-bulls free to take pos- 

 session of the young cows unless prevented by the idle bulls. In 1 914, the idle bulls were 

 sufficiently numerous to secure many of these cows, but a much greater number were 

 seen under the care of the half-bulls. So far as known, the half-bulls are sexually as 

 potent as the older animals, but since they would not do service under natural conditions, 

 some doubt attaches to the advisability of an artificial condition which permits them to 

 act as sires. It may therefore be concluded that idle bulls as a class have a definite func- 

 tion in the breeding economy and that unless in excessive numbers they are a benefit to 



the herd. 



IDLE BULLS AS A MENACE TO THE HERD. 



In recent years there has been no opportunity to observe the effect of numerous 

 idle bulls, but there can be no doubt that a large supply of idle males, including animals 

 of 7 years of age and over, would cause increased fighting and disturbance. The extent 

 to which this would entail increased loss of life is to a considerable degree a matter of 

 opinion. If left to itself, the herd would undoubtedly develop an excess of bulls beyond 

 all possible needs and one which might serve as a distinct disadvantage. It may readily 

 be believed that superabundant male life was a factor in maintaining an equilibrium 

 before the advent of man, but in spite of this a considerable proportion of idle bulls 

 may not be seriously detrimental. Under present conditions the massed sections of 

 the larger rookeries are at the height of the season as thickly packed with seals as seems 

 possible. The harems merge one with another to such an extent that those toward 

 the center of a given area are thoroughl}' shielded from any disturbances except those 

 originating within themselves. On the flat and adjoining beach under Hutchinson 

 Hill there were in 191 4 more than 100 contiguous harems and 6,000 to 8,000 closely 

 packed cows. Numerous idle bulls, if present in such a place, would have caused some 

 extra commotion around the outskirts of this breeding ground, but the great central 

 mass would have been practically unaffected. In a large herd a few bulls and a certain 

 number of cows undoubtedly come to death through fighting, and a considerable num- 

 ber of pups are trampled and smothered, but there is no conclusive evidence that the 

 number is appreciably more than proportionate to the size of the herd, regardless of 

 a considerable number of idle bulls. In 1896, when idle bulls were present in great 

 numbers, 131 dead cows and 28 dead bulls were noted, and a full count of pups was 

 made on at least one rookery, Kitovi. So far as these figures can be compared with 

 those of recent years, when both harem bulls and idle bulls have been at a minimum. 



