ALASKA FISHERY AND FUR-SEAL INDUSTRIES, 1920. 113 
This leads to interesting speculation upon the comparative mor- 
tality of the sexes. But it will be sufficient here to dismiss the subject 
with the observation that no record is known to me of any individual 
bull having returned to the rookeries for more than three successive 
years. It is believed, however, that in the majority of cases they do 
return for at least five years. 
Undoubtedly a mistake was made once in the branding in sorting 
the sexes, and a male pup got the mark across his back. He developed 
and occupied the same position on East Cliffs Rookery for three suc- 
cessive years, 1913, 1914, and 1915 In his last year he had to be at 
least 12 years old. 
BULLS. 
HAREM AND IDLE BULLS. 
At the height of the breeding season the bulls which had harems 
and those usually termed idle were counted with the greatest possible 
uccuracy. Steps have already been taken to adopt certain rookery 
improvements whereby this important count can be continued in the 
future, regardless of how large the herd becomes. Experiments with 
a stable skeleton tripod in 1920 demonstrated the superiority of such 
a structure over any form of elevating apparatus previously tried. 
The manner in which this was used is shown in figure 3. 
By placing such a tripod near the beach line and having a skeleton 
walkway leading to it over the seals, a cheap and very effective 
means of counting large flat areas will be provided. It is expected 
that this will be tried out thoroughly in 1921. A few permanent 
markers on the breeding areas to divide them into sections should 
enable the enumerator to have absolute confidence in his result. 
On account of the absence of some trustworthy manner to get up 
high enough to view the rookeries the harem counts since 1917, when 
bulls became very abundant, have not been as good on the large 
rookeries as desired. Many expedients have been used to help, such 
as counting from a boat, erecting markers of driftwood, climbing a 
long ladder, as well as natural elevations, which are sometimes 
reached with great danger; but all were more or less makeshifts, 
which it is planned shall be abandoned. 
Although there doubtless is an error in the number of harems given 
for the larger rookeries, it is really very small and is conservatively 
estimated to be not greater than one-half of 1 per cent. The desir- 
ability of having even this small variation corrected is due to the fact 
that this is the basis of the census. A small error here will multiply 
throughout the computations. 
The decrease in the number of bulls from 1919 was apparent not 
only in the records; on the rookeries it was very much safer to ap- 
proach counting points, and disturbance of even the rear harems 
rarely resulted. There appeared to be a general “loosening up” of 
the compact areas maintained when the bulls were stationed closer 
together, so that the increase of area over 1919 appeared to be more 
than the figures indicated had been the increase in cows. 
If it is possible to do so in the future, the counting dates on St. 
George Island should be set back to correspond with the beginning of 
the count on St. Paul Island. It has heretofore been customary to 
54777° —21—_8 
