THE SOUTHERN SEA LION* 161 



Under estimate B the herd accordingly numbers (1937): 

 Pups, count, adjusted 



Cows, by inference 

 Bulls, by calculation 

 Immature males 

 Immature females 



83.879 

 83.879 

 53.277 

 94.488 



73.977 



Total 389,500 



The total is about 5 per cent larger than that of estimate A. 



FUTURE PROSPECTS OF THE HERD UNDER COMMERCIAL UTILIZATION 



From the economic point of view the herd is of interest solely as a source of oil- 

 production, and its value as such depends entirely on the number of bulls in excess of 

 those required for breeding. 



Bulls are required in the ratio of one to each 7-5 cows (1934, p. 3 1 5). 



Estimate A. The 80,555 cows required 10,741 bulls, and the bulls in turn require 

 16-66 per cent annually to maintain their numbers against natural deaths, that is 1789. 

 The annual accession of bulls is 11,503, which gives an annual surplus of 9714 bulls, 

 a constant figure so long as the herd retains its present size. 



Estimate B (1937). 83,879 cows will require 1 1,184 bulls, and these entail an accession 

 of 18-66 per cent, that is 2087. 



The number of bulls becoming adult is 13,416, which would provide a surplus in that 

 year of 11,329 or 13 -51 per cent of the counted cows. According to computations 

 regarding the five subsequent years the surplus increases at the approximate rate of 

 2 per cent. So far the accumulated bulls have been ignored. 



Virgin cows. In addition to the cows which have pupped there would be annually a 

 large number of virgins coming up annually for service. Under A this is the constant 

 number of 13,479 an< ^ under B it is 16-5 per cent of the cows which have pupped, in 

 1937, i.e. 13,832. The total number of cows requiring service is therefore A, 94,034 or 

 B, 97,711. If the supply of bulls were reduced to the calculated number required for 

 service, at the rate of one bull to 7-5 of the parous cows, the actual number of cows for 

 service by a bull would be 8-17 (A) or 8-74 (B). Both of these numbers are below the 

 figure which has been proposed as a suitable basis for management of the herd, that is 

 nine cows per bull (1934, p. 303). 



It has been so far assumed that the stock of bulls has been reduced to the number 

 calculated as being required for service. If this were not done, but an annual killing of 

 10,000 made, the effect on the herd would be that, under estimate A, the stock of bulls 

 would gradually diminish for over fifty years and would then arrive at a state of equili- 

 brium when there would be 19,024 bulls before and 9024 after killing, with a constant 

 annual accession of 11,503, which would naturally take place at the breeding season 

 when the young bulls become six years old. All the bulls would obviously have opportu- 

 nity of service before the killing. It follows that there should be an ample supply of bulls 

 for breeding purposes since 19,024 bulls would entail only 4-94 cows each. 



Under estimate B the number of bulls reaching maturity in 1937 would be sufficient 



