Two Fur Seal Problems and Their Solution' 



By U E O R G E A R CI H I B A L D CLARK 



Academic Secretary of Stanford University 



A PROPERLY informed breeder of cat- 

 tle would know the ultimate or aver- 

 age age which his breeding stock 

 might be expected to attain, and the annual 

 increment of young breeders. Such knowl- 

 edge would be considered fundamental to 

 successful breeding of any of our domestic 

 animals. 



The United States Government is engaged 

 in the breeding of fur seals on the Pribilof 

 Islands in Bering Sea, and has been for fifty 

 years, but has not yet definitely ascertained 

 these two important facts with regard to its 

 seal herd; and until five years ago no real 

 progress was made toward ascertaining them. 

 When we consider the amount of investiga- 

 tion to which the seal herd has been sub- 

 jected in the last twenty -five years, this seems 

 an incredible statement, but the explanation 

 is simple — no investigator has ever been al- 

 lowed opportunity to study the herd for more 

 than two seasons in succession, and to solve 

 the first of these problems would require at 

 least fifteen years of close, systematic study. 

 The solution of the second problem is de- 

 pendent upon the first and has, in addition, 

 elements of its own which have required five 

 seasons to solve. 



These problems are not so simple in the 

 case of seals as in that of domestic animals. 

 A cattle man can send out his cowboys and 

 round up his herd at any time ; he actually 

 can count the various classes of animals. The 

 fur seals, however, get all their food in the 

 open sea and spend the winter in a long mi- 

 gration far from the reach of man. They 

 can never all be brought together at any one 

 time. The animals do not carry upon them- 

 selves any distinctive age markings. The 

 seal which has begun to decline ever so lit- 

 tle in strength and efficiency succumbs to the 

 harsh conditions of the northern winter ; only 

 those in prime condition and physically fit 

 return in the spring. 



The three-year-old females, which consti- 

 tute the breeding increment, come upon the 

 breeding grounds gradually and mingle with 

 the adult females, being indistinguishable 

 from them. The two-year-old females, hav- 

 ' Read before tlie Western 



ing no young, are even less recognizable as 

 a class, while the yearlings of both sexes 

 keep to the sea for the most part in the 

 breeding season. The two, three, and four- 

 year-old males, the animals from which the 

 product of the herd is taken, are irregular 

 in their movements. They frequent hauling 

 grounds separate from the areas occupied by 

 the breeding seals. The method of taking 

 the quota is to have these hauling grounds 

 driven each week during a season of from 

 six to eight weeks. Animals of approxi- 

 mately three years of age only are taken; 

 the others are returned to the sea. New 

 three-year-old animals are found each time, 

 and the killing season closes early in Au- 

 gust, not because of exhaustion of the sup- 

 ply of killable animals, but because of an 

 undesirable condition of the skins due to 

 shedding. It is not possible, therefore, to 

 determine the number of three-year-olds 

 even by the process of elimination. Natu- 

 rally no enumeration of the two-year-olds, 

 driven and redriven as they are, can be made. 

 Of the breeding seals, it is possible to make 

 an exact count of the harem masters because 

 of their large size and the fact that they do 

 not change their positions during the breed- 

 ing season. The breeding females, however, 

 come and go in the sea, and never more than 

 one half of them is present on land at any 

 one time. In short, aside from the breeding 

 males — the smallest element in the herd — 

 there is no direct way of enumerating any 

 class of the grown animals. Fortunately the 

 pups of the season do not take to the water 

 during the first month or six weeks of their 

 lives, and at the close of the breeding season 

 can be driven up and counted. As each 

 breeding female has but one pup the count 

 of pups is equivalent to a count of females, 

 and from this known element of the pups a 

 fair approximation of the other nonbreeding 

 animals can be arrived at. 



These problems are not merely difficult in 

 the case of the fur seal; they are unusually 

 important. It is vital to the life of the seal 

 herd that the killing of the males should not 

 be so close as to leave an insufficient reserve 

 Society of Naturalists, 1917. 



497 



