298 DISCOVERY REPORTS 



recognized one in coitu, and from the results of the counts of site No. II set out on p. 308 

 it appears that they do not join the harems, which are only used by the cows about to 

 give birth. 



In two of these counts the number of cows varied from 212 to 223 with an average 

 of 217, and the number of pups, counted a little later, gave an average of 255. There 

 were counted, in fact, more pups than cows, so that, since no cow ever produces more 

 than one pup at a time, there could hardly have been any virgins in this rookery. 

 It seems likely that the virgins are covered by idle bulls as opportunity offers, and it 

 may even be suggested that abortion may be the result of excessive attention, since idle 

 bulls are so numerous. Failure to conceive might also result from the excess of bulls, 

 for the virgin cows could escape, as solitary cows often do, while the males were engaged 

 in fighting. 



From an examination of the available ovarian material it appears that the potential 

 breeding season is very much longer than that which is so obvious : the true nature of 

 things is concealed by the rapidity with which the cows come on heat after parturition 

 and in normal circumstances the immediate availability of a bull. That there are other 

 possibilities is shown by the condition of No. 1065 which contained an almost ripe 

 follicle and would thus shortly have been available for impregnation, although the 

 animal was killed on July 19, about six months distant from the "breeding season". 

 Moreover, seven cows killed on June 8, 9 and 10 were all pregnant, with foetuses of 

 comparable size, from 83 to 127 mm. in length; but No. 1030, which was killed on 

 July 29 had a foetus with the great length of 269 mm. which could not possibly have 

 been begotten at the same time as the others, even if allowance is made for the 

 additional seven weeks. 



The data are not sufficient to permit of any statement as to the oestrous cycle in 

 this species. 



BREEDING HABITS 



Outside the breeding season all stages of the sea lion are more or less mixed together. 

 As summer approaches the breeding and non-breeding animals separate, but many 

 of the previous season's pups remain with their mothers until the next are born. The 

 two sections of the community have their own separate parts of the beaches ; but odd 

 members of either section may occur on beaches which properly belong to the other, 

 and on their own resorts the numbers of the non-breeding animals vary from day to 

 day — the sea lions are constantly coming and going and shifting about. 



The non-breeding herd contains all the immature seal, some of the previous season's 

 pups and many of the idle bulls — bulls which have not been able to secure cows 

 (Plates V, VI, VII). 



The breeding herd consists of the harem bulls, the pregnant cows about to give 

 birth, the newly born pups and the virgin cows. There is also a fringe of idle bulls, 

 many of them the newly adult, while well-grown immature males appear from time 

 to time but are always on the move. 



