THE SOUTHERN SEA LION 309 



The average is 257, while the variation in either direction is comparatively small. 

 Although just at this season any one count of adults does not very seriously depart 

 from an average, as more and more cows are covered by the bulls the counts quickly 

 become much less reliable, since the cows then resort to the sea in ever increasing 

 numbers and return to suckle the pups at irregular times. As soon after the date of 

 the last count as January 23 only 190 adults were found on this stretch of beach. 



Counts of two groups of pups were made in the same way. This class is certainly 

 all ashore at the same time, but their small size and restlessness makes counting 

 difficult; at times it is indeed impossible, such as at low water on a wide beach, when 

 they are spread all over the beach and into the shallow water and are most energetic. 

 In spite of the difficulties a count of pups is preferable to all others, although a count 

 of breeding cows in the earlier part of the season is, as has been shown, tolerably 

 reliable and it is certainly easier to carry out. 



The counts of pups made on two sites are as follows : 



No. on site II 



232 

 269 

 244 

 286 

 246 



By the date of the next count, February 13, the breeding organization was much 

 broken up and many of the pups had moved away; the numbers seen were: site I, 336 

 and site II, 217. Counts of pups therefore should if possible be carried out between 

 January 21 (the date of the last observed birth) and the end of the first week in 

 February. 



To sum up, counts of cows may be made up to the end of the third week in January, 

 but thereafter pups only should be counted. 



RATE OF INCREASE 



The rate of increase is a matter of importance with reference to the future of the 

 herd. It depends on two factors, birth-rate and death-rate. As to the first, this is 

 dependent on the length of life of the cows and on the age at which they first give birth. 

 The evidence points to the occurrence of the birth of the first pup when the cow is 

 five years old, and it is suggested that seven years would be a reasonable length of 

 breeding life to allow; therefore each cow, apart from accident, would bear seven pups 

 during her life. There is no means of arriving at the death-rate at present ; that it is 

 heavy during the first year is shown by the finding of so many dead pups, and judging 

 from the increased rarity of dead seals in subsequent stages, it declines after the first 

 year. Man does not molest the species to any serious extent, except as regards the 

 activities, of late years, of a small commercial sealing company. 



The northern fur seal is the only Otariid of which there is information as to the 

 length of life and the death-rate in the natural state. The death-rate of the males is 



D vni 



