314 DISCOVERY REPORTS 



With the exception of the last catch all the animals were killed at one of two places 

 which had been industriously worked all winter ; I incline to believe that the October 

 catch included a proportion of not quite mature animals, since it is hardly reasonable 

 to suppose that the adult bulls begin to fall off in condition shortly before the breeding 

 season, and their physical appearance at that time does not justify the idea. 



The total number of seal in the table is 4563, which produced 56,182 gallons of oil, 

 equal to 1404-54 barrels of 40 gallons each or 234-09 tons. During a working period 

 of seven months the average production of oil was 12-31 gallons per animal, var^'ing 

 from about 8 to about 14 gallons according to the season. From 2-8 to 5 sea lions are 

 therefore the equivalent of a standard barrel of oil and from 17 to 30 the equivalent 

 of a ton. The mean of 2-8 and 5 is 3-6 which gives a value of ii-o gallons per animal, 

 21-6 (say 22) sea lions to the ton of oil, and 45 tons per 1000 animals. The present price 

 of seal oil is in the neighbourhood of j(;i5 per ton, and if 22 sea lions produce a ton of 

 oil, this gives a value of 135. 7^. to each animal, exclusive of the value of the hide, if any. 



The sea-Hon herd in the Falklands is very large: it is not outside the bounds of 

 possibility that it may exceed 100,000 head. It must therefore be regarded as an asset 

 to the colony, containing as it does potentialities for the supply of oil and hides for an 

 indefinite period, if properly managed. It cannot therefore be too strongly urged that 

 every effort should be made to encourage this animal and to maintain the breeding 

 herd in its highest state of efficiency. 



Having regard to the great excess of adult males the herd would benefit by selective 

 killing and might achieve a more rapid rate of increase. The continual fighting and 

 trampling about in the rookeries and the single cow harems represent definite waste, 

 for each bull can look after a number of cows. 



In using the sea lions as a source of supply for oil the killing must he restricted to 

 adult males, since they are the only class which can be reduced without risk of damage 

 to the herd. There is an excess of bulls much beyond the breeding requirements, and 

 the bulls are also the most remunerative to work. A reservation must be made for 

 breeding purposes, and the proportion of the bulls to be reserved depends on two 

 factors : (i) the sexual capacity of the bulls, and (ii) the rate of increase of the sexually 

 mature cows. 



The sexual capacity of the bulls has been discussed, and on p. 304 it is suggested that 

 a proportion of one bull to every nine cows is desirable, to start with at any rate. 

 As for (ii) it is clear that the annual increase cannot be very great owing to the sub- 

 stantial death-rate in the first, and although to a less degree, in the subsequent immature 

 years also. The northern fur seal cows increase by 8 per cent per annum and the 

 Falkland Islands fur seal as a whole had increased by 50 per cent in the seven years 

 preceding 1930; on calculation this represents an average increase of about 6-o per cent 

 per annum. The sea lion is tolerably closely related to the fur seal, and is a good deal 

 larger and therefore the less liable to the attacks of other animals. In the entire absence 

 of any other guide it seems not unreasonable to adopt 8 per cent per annum as a 

 provisional figure for the rate of increase of breeding sea-lion cows, and since there 



