88 ALASKA FISHERIES AND FUR INDUSTRIES IN 1915. 
per cent deducted from the 93,250 breeding cows in 1914 leaves 83,925 for 1915. This 
deducted from the number of breeding cows present in 1915 leaves 19,602 as the number 
of 38-year-old cowsin 1915. That is, this isthe number left of the 40,992 females born in 
1912, assuming, of course, an equal birth rate. Very close to 50 per cent of those born 
have therefore survived. The best figures obtainable previous to this were gotten in 
the days of pelagic sealing and amounted to 61 per cent loss the first three years. 
The natural mortality for each year of the first three can not be determined accu- 
rately. But in order to estimate the number of seals in each category, arbitrary per- 
centages of loss must be assumed. After carefully considering the conditions involved 
these have been tentatively placed at 35 per cent loss the first year, 20 per cent of the 
remainder the second, and 4 per cent of the remainder the third, which aggregate 50 
per cent loss during the first three years. 
Harem bulls and idle bulls —Harem bulls and younger bulls, some of the latter be- 
coming idle bulls later in the season, are the first seals of the herd to: appear at the 
islands in the spring. Forty came to Sea Lion Rock on April 14, 1915. For several 
days after their arrival the bulls slept at the water’s edge, and not until May 2 did 
one get into position on Reef Rookery. 
Not much fighting occurs until after a considerable number of cows have come into 
heat, and then it is more among the idle-bull class than among the harem masters. 
When an idle bull starts down through a rookery a great deal of commotion is caused 
and the bulls near by all start for him. Some bulls will leave their own harem and go 
through five or six others after a young bull on such occasions, yet this harem master is 
unmolested by the masters of the harems through which he passes. Battles to a finish 
are of common occurrence, as the evidence shows, but they are seldom witnessed. 
The injuries thus received sometimes cause death. <A large number of young bulls 
were seen on the hauling grounds through the latter part of the breeding season so 
badly crippled they could scarcely travel. 
In many ways the count of harems is the most important census work which can be 
done on the islands. But to be of greatest value, each rookery should be counted on 
exactly the same date from year to year. The dates established by the 1914 investiga- 
tion well represent the height of the breeding season. In 1915 this count was made 
between July 17 and 21, each rookery being counted on the same date asin 1914 with the 
exception of Sea Lion Rock, which was one day later owing to inclement weather 
conditions. The charts of the rookeries published by the Coast and Geodetic Survey 
were taken in the field and the positions of the breeding masses and all outlying harems 
were plotted as nearly exact as was possible without instrumental aid. By locating 
the white numbered rocks and natural Jandmarks which are on these charts, the lines 
of breeding masses can be located with a margin of error of only afew feet. The ground 
which had been hauled over by bachelors was likewise plotted on the same charts 
during the harem counts. 
On St. George Island the breeding and hauling areas were not plotted until the pup 
count, August 5 to 7. A. H. Proctor had recorded the number of harems between 
the white numbered rocks and other landmarks on July 19 and 20, and the breeding 
area does not change appreciably between the harem and pup counts. The margin 
of error of the areas as plotted for St. George is slightly greater than for St. Paul, but is 
believed to be sufficiently exact to be of considerable value in 1916 in showing rookery 
expansions. 
The number of pups in each breeding mass was also recorded separately during the 
pup count and from these counts it is possible to determine the average harem for 
each mass. This shows the variation on each rookery perhaps better than any other 
method. 
The numbered rocks are of very great value in making the harem count. In large 
breeding masses especially, it is impossible for the eye to grasp the entire mass with- 
out a mark or rest of some kind. It is necessary that some of these numbers which 
