304 DISCOVERY REPORTS 



safely be adopted as a working basis, particularly since it is below the average harem 

 of 237 per cent of these bulls. There is of course in this herd, untouched like most 

 of those in the Falklands, a very large excess of males and this is the reason for the 

 large percentage of small harems. It might be found that the figure of 9 is too low to 

 work to, in order to take full advantage of the economic value of the herd. I have seen 

 a bull with 17 cows, but am unable to say if he was able to keep them all. 



Reverting to the total cows in the count of 2298 sea lions, their number was 1984, 

 and on the basis of 9 cows to each bull they would require only 230 bulls, which gives 

 an immediate surplus of 84 of them not required for breeding. 



IDLE BULLS 



Besides the harem bulls there is always a considerable but varying number of adult 

 males, "idle" bulls, hanging about the borders of the breeding rookeries. These 

 animals cannot be accurately counted, since, having no attachment to one part of the 

 beach, they are always moving about and at times retire to their own particular beaches, 

 which are not used by the breeding herd, in order to sleep : there is always a chance 

 that some of them may acquire a cow and thus cease to be idle bulls in the strict sense 

 of the term. Their numbers are usually tolerably high compared with the harem bulls, 

 on a stretch of beach containing 150 bulls, 88 of them had harems of more than one 

 cow, 27 had one only and 35, or 23-3 per cent, were idle bulls. 



If, as there is every reason to suppose, the sexes are born in equal numbers, and if 

 there is no selective death-rate (of which there is no indication), the number of adult 

 bulls should equal the number of breeding cows since they are of the same ages ; but 

 if this is so it is clear from the work on Cape Dolphin that all the bulls are not ashore 

 there at one time. There were indeed some hundreds usually to be found at two 

 particular places, as is indicated on p. 298, but there were not bulls equal in number to the 

 estimated number of breeding cows — 4500. An explanation of such apparent deficiencies 

 may be found in the accumulations of bulls which are found sometimes at places where 

 there is no breeding herd at all, or next to none. Thus, in the neighbourhood of 

 Macbride Head in East Falkland there were at the end of December two places where 

 small breeding rookeries were established. At one there were 40 breeding cows and 

 69 bulls and at the other there were about 250 cows and only 10 bulls: the nature of 

 the ground, however, made an accurate count impossible. Between these two places 

 and at least a mile distant from each are two bays, and in one of these there were 364 

 and in the other 63 1 bulls of Otaria (Plate V, fig. 2) ; and farther to the east there was 

 another company of 30 bulls in a small valley. At Macbride Head there were five 

 cows and in the valley one. There were thus 296 cows and 1 104 bulls in this locality, 

 a surplus of bulls so great that it could not possibly have originated from the little 

 breeding rookeries in the neighbourhood. It is an interesting speculation whether 

 Cape Dolphin may not have been the origin of the majority of these surplus males, 

 since it is the only large breeding rookery within a reasonable distance. 



Again, at Cape Meredith on West Falkland 271 cows were found in January on the 



