THE SOUTHERN SEA LION 163 



NOTES 



ON MIGRATION 

 After the breeding season the herd at Cape Dolphin gradually becomes smaller, and 

 it continues to diminish as the winter progresses. A count in August gave a figure of 

 2545, including 183 bulls. With the approach of the breeding season the seals reappear, 

 the bulls selecting sites on the beaches and being there joined by the cows. This 

 repopulation takes the form of a gradual filling up from the north end of the rookery. 

 By the middle of January the herd is reconstituted. A count on 20 January showed 

 5854 seals, including 723 bulls. 



At nearly all times there is a considerable amount of coming and going between the 

 land and the sea and it is therefore inevitable that there should be some variation in the 

 composition of the herd. It is nevertheless quite clear from constant inspection that the 

 great diminution in counted numbers represents a real reduction of the herd and that 

 the minimum is to be found in the middle of winter. 



There is undoubtedly some local movement. It has been observed to a limited 

 degree, but I consider that there must also be a genuine partial migration, at least in the 

 sense that the seals leave the islands, although it may be that they go no farther than 

 certain feeding grounds which are known to exist and where one expects to see not only 

 seals but birds and whales, most usually Balaena physalns, an area such as that about 

 120 miles N2 W from Cape Pembroke. 



I have observed on more than one occasion the occurrence of a quite unusual and 

 conspicuous congregation of seals on the extreme northern end of Cape Dolphin. On 

 12 December there were 1084 adult or almost adult males and 186 cows at this place, 

 where there had been only 243 males but about 500 cows on 5 December. The import- 

 ance of such concentration lies in the fact that the population normally contains nothing 

 approaching such numbers of bulls and cows. Of the latter there were 105 v/ith 27 pups 

 on 21 January, 67 with 13 pups on 3 February and on 4 February (of the previous year) 

 there were 45 cows and 23 pups, these numbers representing the ordinary state of 

 affairs at this site. Further, on 13 December of one year I saw a herd of perhaps 500 

 seals some distance off shore to the north; they were gradually drawing in to the land 

 and presently began to come ashore. The unusual features of this phenomenon were that 

 the herd was all moving steadily in the same direction and that there was no reason to 

 believe that they were feeding, since no sea birds were attracted to the same area of 

 water, as would have been the case if there had been feed there. 



Having regard to the behaviour of the seals, the absence of signs of feed and the time 

 of the year I am compelled to adopt the view that this was a party returning from 



migration. 



In this connexion it is interesting to recall Devincenzi's statement that from Lobos 

 Island there is in early winter a migration to the South. Such a movement would be in 

 the direction of other known feeding grounds. It seems possible that a large part of the 

 Otaria herd of the Falklands may put to sea in winter as the whole herd of Calorhinus 

 does in the Pacific. 



