234 DISCOVERY REPORTS 



FOOD 



The food of the Sei whale at South Georgia consists entirely of the Euphausia superba 

 krill that is eaten by the other species of balaenopterids. Table XVI summarizes the 

 information obtained from the examination of 171 stomachs. The rather high proportion 

 of empty stomachs, and stomachs with little krill, at South Georgia is no doubt due to 

 the fact that Sei whales are not taken when the larger species of whale are abundant, 

 and consequently are usually brought in to the whaling stations only when there is a 

 shortage of krill in the surrounding waters. This table, therefore, tends to show the 

 periods when krill was scarce on the whaling grounds, rather than the type of krill in 

 its periods of abundance. On the whole it may safely be stated that the Sei whales at 

 South Georgia are either feeding or in quest of food. 



On the other hand, the few records from South Africa show that food is very scarce 

 there. In none of the stomachs examined was krill found: only two contained any 

 traces of food at all. In these two stomachs a small quantity of remains of "tiny 

 Crustacea" were recorded. It would appear probable that these two whales had been 

 feeding upon copepods, as do the northern Sei whales according to Millais (1906), who 

 states that they feed exclusively on small Crustacea such as Euphausia inermis, Calonus 

 finmarchiciis and Temora longicornis. In South Georgian waters, however, no preference 

 for smaller Crustacea is shown, as the accompanying analysis of five stomach contents 

 given in Table XVII demonstrates. 



It has been shown elsewhere (Matthews, 1932) that off the Patagonian coast the Sei 

 whale feeds almost exclusively on the crustacean Munida gregaria and its pelagic post- 

 larval stage, Grimothea, which occurs in swarms near the surface of the sea and is 

 known as "lobster krill". On the Pacific coast of Mexico, too, this whale feeds on 

 shoals of an allied crustacean, probably Pleuroncodes planipes. 



Collett (1886) records that the northern Sei whales off the Norwegian coast feed 

 largely on Calamis finmarchiciis, and correlates the fine texture of the baleen with the 

 small size of this crustacean, but he also states that the Sei whale feeds as well on the 

 larger krill, Thysanoessa inermis, that is eaten by Blue whales in that locality. 



BLUBBER 

 Data of the blubber are recorded from 107 Sei whales, mostly for the months of 

 February, March and April, at South Georgia. When the average thickness of the 

 blubber is plotted against the total length of the whale the curves shown in Figs. 64 

 and 65 are obtained for each sex respectively. These show that on the whole the 

 thickness of the blubber depends upon the total length of the whale, and also that the 

 Sei whales in South African waters are thinner than those at South Georgia, having 

 blubber about 1-5 cm. on the average less in thickness. There appears to be little 

 significant difference in blubber thickness between the sexes, but the difference in 

 blubber thickness between South African and South Georgian whales is found in both. 

 This difference is very much more marked in the Sei whale than it is in the Fin and 



