THE SOUTHERN SEA LION 315 



is no indication of a selective death-rate at present, it may be adopted as the figure for 

 the rate of increase of the bulls. The bulls become adult at the same age as that of the 

 females when they produce their first pup, and it will be remembered that it is on the 

 counts of the breeding cows or the pups that a census must be based. 



As an illustration of the way in which this assumed rate of increase may be used 

 the Cape Dolphin rookery may be considered. There are here, in round numbers, 

 4500 breeding cows ; these will require 500 bulls, and the increase of 8 per cent (360) 

 will require a further 40 bulls at the allowance of nine cows to one bull. An allowance 

 must be made for stray cows and for virgin seal coming up for service for the first 

 time; 10 per cent should be sufficient for this, and a further 10 per cent should be 

 allowed for unforeseen factors, bringing the total reservation to 648 bulls. Since there 

 are as many bulls as there are breeding cows there will be 4500 of them, and this, less, 

 let us say, 650, gives the figure of 3850 as the number of surplus bulls. If, for the sake 

 of convenience, the killable surplus is taken at 3500, seven bulls may be killed for 

 every nine breeding cows and on this basis 77 per cent of the catch analysed on p. 313 

 could have been taken from the herd based on Cape Dolphin. 



To sum up, with an increase of 8 per cent bulls in the untouched herd may be killed 

 until the catch represents 77 per cent of the counted breeding cows and thereafter a 

 number of bulls equal to the difference between the increase of the bulls (8 per cent 

 per annum) and the number of additional bulls required to serve the additional 8 per 

 cent of cows. Thus of the increase of 360 bulls mentioned above, 40 would be required 

 for the 360 additional cows, leaving 320 as surplus — almost exactly 7 per cent of 4500, 

 the total number of cows. As a precaution the lower figure of 6-5 per cent of the 

 counted cows should be used to calculate the number of bulls which might be killed 

 annually. 



There is good reason to suppose that the sea lions of the Falklands can be exploited 

 profitably, and that if due precautions are taken a sealing industry can be established 

 on a permanent basis. Hitherto only a few of the existing rookeries have been worked, 

 and even on these many more bulls can be taken before the accumulated surplus of 

 this sex has been removed. In a revival of the industry it is important that operations 

 should be spread over all the herds and not limited to a few of the more convenient 

 sites, and efficient supervision of all sealing will be indispensable. Even if all the 

 rookeries are exploited some years must elapse before the surplus bulls are removed, 

 and by this action, as already noted, definite improvement in the herds will be efl^ected. 

 Thereafter, when the surplus of adult males is exhausted, the extent of the industry 

 must be regulated on the lines set forth in this report, each herd yielding annually 

 6*5 per cent of its total number of bulls. Regulation can only be based on an adequate 

 census of the herds, and to take such a census is obviously a matter of considerable 

 difficulty. Few of the rookeries are easy of access, bad weather will hinder operations, 

 and as explained on p. 309, there are only two short and consecutive periods durin 

 the season when the work can be undertaken. 



