1899] THE HABITS OF THE NORTHERN FUR SEAL 39 



the average number on shore at any one time being about 24 per 

 cent, and the consequent average number of absentees from the beach 

 about 76 per cent. 



An almost equally variable number of females, whose minimum 

 was about 17 and maximum about 68, with an average of over 37 per 

 cent, was always to be found on the reef or on the rocks close to the 

 rookery. As the pups also frequented these rocks in numbers, except 

 at high tide, and were there met and suckled by their mothers, I am 

 of opinion that these seals may be regarded as also having been on 

 the rookery beach, and that the two lots together must be regarded as 

 equivalent to the counts of seals made at any rookery (and there are 

 many such on the Pribilofs) where the beach is not protected by 

 outlying reefs or rocks. In other words, it seems that the percentage 

 to be added to the number of seals on shore, in order to account 

 for the total number belonging to the rookery, must be different accord- 

 ing as the rookeries are protected or not. In the former case it would 

 be much more than in the latter. 



Adding the number of seals found on the beach to those on the 

 reef and neighbouring rocks, it is seen that, although the items are so 

 variable themselves, the total is more constant, never falling below 

 about 26 per cent, or rising above about 85 per cent, and with a 

 pretty constant average of about 62 per cent. In other words, the 

 variability of the numbers of seals on shore or on the reef was due to 

 the movement of the seals from one locality to another, and not to 

 their departure from the rookery. 



Besides this average of about 62 per cent of seals which were 

 never absent from the vicinity of the rookery, and the numbers of 

 which were ascertained in all cases by actual count, there was a further 

 number who were never far away and always in sight. The numbers 

 of these could only -in a few cases be obtained by actual count, and 

 must be, therefore, regarded as estimated only. The figures are, how- 

 ever, as likely to be under as over the mark. The numbers of these 

 seals were also variable, falling once to nearly 2 per cent, and rising 

 to above 62 per cent, and having an average of about 21 per cent. 



Combining these figures, I find that there was no occasion on 

 which I could not account for over 65 per cent of the total number of 

 cows, that on one occasion I could account for over 90 per cent of 

 them, but that these figures must be regarded as extremes, the average 

 number of cows accountable for during a series of sixteen observations 

 being about 83 per cent, and the average percentage of absentees 

 being, consequently, about 17. 



There would appear at first sight to have been a slight increase in 

 the number of absentees while my observations were being conducted, 

 but a closer look at my figures 1 shows that there was no day on which 

 there were not at one time or another at least 83 per cent of the seals 



1 Which are too long to be printed here. 



