19 



their birthplace, furnish the only "snre guide to the whole number of seals on the 

 rookeries." 



Assuming the supposed liiw that the roolvcries arc always e([ually crowded every- 

 where in tlie height of the season, and estimating 2 square feet on the average 

 for each seal, old and young, he tinds on the two islands 6,3S(J,810 feet of rookery 

 sjjace, representing a. total of 3,193,420 breeding seals and pups, or about a million 

 breeding females. 



This estimate, while containing many elomtints of error, and, in our judgment, 

 nearly 70 per cent too high, is still not so far out of the way as it appears at first 

 sight. It is certainly true that a cow occupies ordinarily more than 3 square feet 

 and a pup more than 1. On the otlier hand, Mr. Elliott is right in saying that in a 

 few days or a weelv aftar the birth of the pup "' the cow takes to the water to 

 wash and feed, and is not back on this allotted space one-half the time again dur- 

 ing the season." Some other cow returning occupies the 3 feet allotted to her. 

 Even in the height of the season the poi)ulation of the rookeries is constantly 

 changing, the earlier cows being away before the new ones come, and the real size 

 of a harem being nearly double the largest number of cows counted, liesides this, 

 'the return of the virgin females and belated females in late .Inly greatly extends 

 the rookery space itself beyond the outlines taken in these measurements. In 1S90 

 Mr. Elliott found 1,S18,7N6 square feet of breeding space on the two islands. This 

 was supposed to represent a total of 959,393 breeding seals and pups. It would 

 appear that the rookeries were less exactly measured than in 1(S74, as an allowance 

 by estimate was made on each one on account of the thinning out of the seals. In 

 any event, in spite of the fact that there were at least lialf juoro seals in 1890 than 

 in 1895, the estimates of acreage m;ide by Messrs. Townseud and True give for 1895 

 2,616,063 s(|uaTe feet. This would give about 77} square feet each for 160,000 seals 

 with their pu]is and 30,000 \ irgin two-year-tdds. 



We can not belies e that even in the most favorable times the fur seals were evenly 

 crowded over the rookeries, and it is evident that as tliey grow fewer their arrange- 

 ment tends to become more sjiarse, especially on rocky slopes and bowlder-strewn 

 beaches. 



Acreage estimates (an only serve us in default of better, but it is fair to early 

 observers to remember that 110 other method of enumeration was i)0ssiblc on a 

 large scale until very lately. 



DIFFICULTIES IN MEASURING ACREAGE. 



It is by no means an easy task to tiud the acreage of any rookery. The length of 

 its sea front is easily ascertained, but its average width is at the liest a matter of con- 

 jecture. It' will sj»read out over le^'el groiind, shrink away ircjui soft sand, climb up 

 the hill in gullies, extend high over cliifs, break at a cove to permit liachelors to 

 land, thin out among large rocks, then widen in great amphitheaters. Its lower 

 boundary fluctuates with the tides. Its extent behind grows day by day with the 

 arrival of late coming seals, and its whole outline is changed in a few days, as the 

 bands of virgin 2- year-olds come into the ranks late in .July. A comparison of the dif- 

 ferent estimates of the number of s(inare feet 0:1 the individual rookeries which luive 

 been already published will show how lai'ge these elements of uncertainty are. A 

 few feet added to the width of any rookery means the addition of thousands of seals 

 to the estimate. 



ESTIMATES OF TRUE AND TOWNSEND. 



The most recent computation of the acreage of seals is that made by ^lessrs. True 

 and Townsend in 1895. Here the number ol square feet is measured from the cur- 

 rent maps, on which the outline of the rookeries has been sketched by the aid of the 

 eye. But the details of the maps were not exactly surveyed and the outlines of 

 the rookeries could not be. 



VAiiiATiONS IN i;ookei;y outlines. 



An element of uncertainty which enters into all estimates based upon observa- 

 tion and conqiarison without exact enumeration is the fact that there is no line of 

 demarcation to show the outer limit of any rookery. The ground for a considerable 

 distance back of the line of harems presents exactly the same appearance as the 

 space occupied l>y the seals. If theie occurs a change of a few feet or yards in the 

 extent of the rookery, it is impos-;ib]e for the eye to detect it. Nor can the vacant 

 space back of the rookeries be relied u]ion to indicate a decrease of territory occupied 

 by the seals. As a matter of fact, after the period of confusion consecjuent upon the 

 arrival of the virgin cows, the depaiture of the old harem masters, and the ingress 

 of the half bulls, the rookeries gradually assume another fixed phase. The cows 



