WHALEBONE WHALES—MACKINTOSH 249 
Ili. FOOD 
The food of whales is an important subject, since it has a close 
bearing on their distribution, and is of interest in relation to the gen- 
eral economy of the oceanic fauna. Some of the larger species of 
planktonic Crustacea, known collectively as “krill,” constitute the 
principal food of the whalebone whales, and it is well known that the 
baleen (or whalebone) plates, of which the inner edges are frayed out 
into soft bristles, form an efficient straining mechanism for taking 
adequate quantities of such organisms. 
It is well established that blue, fin, and humpback whales in the 
Antarctic feed heavily, and virtually exclusively, on the oceanic 
prawn, Huphausia superba (Mackintosh, 1942). This organism is 
confined to Antarctic waters (John, 1936) and often forms extensive 
shoals at or near the surface, mainly where the sea temperature is less 
than 2° C. £. superba holds a key position in the chain of nourish- 
ment of the Antarctic fauna, for it provides food not only for whales 
but also for certain fish, seals, and birds. The majority of whales 
taken in the summer whaling season in the Antarctic are found to have 
plenty of krill in their stomachs, but those taken in winter at stations 
in warmer waters in the Southern Hemisphere are found to have eaten 
little or no food. It is true that these winter catches are not properly 
representative of the main stock, but there is little doubt that the 
majority of whales have little to eat in winter, for at the beginning 
of the Antarctic whaling season the blubber is relatively thin (Mack- 
intosh and Wheeler, 1929), and as the summer advances they become 
fatter and the yield of oil steadily increases (Hjort, Lie and Ruud, 
1938). It is generally assumed that the oil stored in the blubber, 
bones, and muscles acts as a reserve of nourishment for the winter 
(Hjort, 1933), and this may be supplemented by small quantities of 
Crustacea of various species, and occasionally fish. Sei, humpback, 
and right whales are known to feed sometimes in certain temperate 
coastal regions of the Southern Hemisphere, on shoals of the “lobster 
krill” which is the pelagic postlarval (or grimothea) stage of the 
anomuran, Munida gregaria (Matthews, 1932; Rayner, 1935), but this 
is at the best a minor source of nourishment. The staple summer diet 
of the southern right and sei whales when they are in sub-Antarctic 
or temperate waters is not known, but it seems that they also feed on 
Euphausia superba whenever they move so far south as the habitat 
of this species (Matthews, 1938a, b). 
There is much less certainty about the staple food of whales in the 
Northern Hemisphere. In order to determine the principal food of 
any species we need not only to identify the organisms found in its 
stomach from time to time, but also to know whether they are present 
in large quantities and in a majority of whales, and at what times of 
