3o8 DISCOVERY REPORTS 



marks were found on it. It may be suggested that this animal had simply reached the 

 end of his natural term of life and that the great strain of the breeding season had been 

 too much for him. Similarly a very large cow was found dead without marks of external 

 violence ; she was the second largest cow which I handled : she had unfortunately been 

 eviscerated by the birds. 



The leopard seal is responsible for a certain number of deaths. I have had a report 

 of two leopard seals attacking a large sea lion and killing it, and the stomach of one 

 killed in October, when the previous season's pups are quite large animals, was full 

 of lumps of skin and blubber of such pups, as well as other fragments. The leopard 

 seal is so uncommon in the Falklands that it can be of no importance as a menace to 



the sea lions. 



In the Galapagos sharks are stated to eat the pups of Otaria hyronia ; but there are 

 no sharks in the Falklands. Killer whales appear to be extremely rare: I have never 

 seen them and have found only one skull on many miles of beach. Land carnivores 

 are absent, nor are there any birds of prey sufficiently powerful to attack even a pup 

 of Otaria: the species has in fact practically no natural enemies at all in the islands. 



ESTIMATION OF NUMBERS 

 Although the sea lion is to be found at all times in the Falklands it varies considerably 

 in concentration. At the height of the breeding season the number of adults on the 

 rookeries is at its maximum, but after the breeding season the animals begin to disperse 

 and continue to do so during the winter. It is only a short time before the following 

 breeding season that the sea lions begin to concentrate on the breeding rookeries, the 

 bulls taking up their stations before the cows assemble. As late as December 17 a count 

 on Cape Dolphin yielded the following resuU, which includes at least as many bulls as 

 a count in the height of the season: bulls 1650; cows 207; pups 32; other stages 337; 

 total 2226. 



On the Cape Dolphin rookery the maximum number is present about the middle 

 of January: at this time an actual count of the sea lions present came to 6282, of which 

 5346 were breeding animals. Pups are excluded from the total, but immature sea lions 

 and idle bulls are included. This count does not represent the entire herd pertaining to 

 Cape Dolphin, since the immature seal are on the move the whole time and many of 

 the idle bulls take to the water also. The idle bulls may indeed haul up elsewhere, as 

 is suggested on p. 304: they amount to some hundreds. 



In order to determine the day to day variability of the population a stretch of shore 

 containing an assembly with clearly defined limits was chosen for counting at short 

 intervals. The resuh is as follows, the numbers referring to breeding aduhs, bulls 

 which were stationary, and cows : 



Date No. of sea lions on site II 



January 11 250 



12 265 



„ 12 259 



„ 21 253 



