-41- 



feeding strategies identified by Nemoto (1970): swallowers, 

 skimmers, and combination swallowers/skimmers . Swallowers 

 are adapted to feed on dense patches of plankton — often 

 Euphausiids. Skimmers can use sparser plankton patches 

 commonly composed of amphipods, copepods , or decopods . In 

 the Antarctic, blue, fin, minke, and humpback whales would 

 be categorized as swallowers that feed primarily on krill. 

 Antarctic right whales, on the other hand, would qualify 

 as skimmers using amphipods and copepods as primary food 

 sources. Sei whales, combination swallowers/skimmers, use a 

 wide variety of food depending on availability. These three 

 feeding strategies may be one mechanism to allow baleen 

 whales to co-exist in Antarctic waters by partitioning food 

 resources. Other mechanisms which allow greater partitioning 

 of food resources include spatial and temporal segregation of 

 whale stocks (Laws, 1977a). 



Mitchell's (1975) paper on trophic relationships and 

 competition for food among whales noted the likelihood of 

 food competition between whale species. He suggested that 

 trophic relationships among sympatric species might shift as 

 the relative abundance of prey species varies through time. 

 The implied food preference of different whale stocks 

 provides evidence for competitive exclusion between groups 

 of whales. Switching feeding habits to less preferred food 

 items reduces overt competition. The significance of 

 competition among whales and other krill consumers in relation 

 to the decline of the great whales will be discussed later. 



2. Toothed Whales 



Nishiwaki (1977) recently reviewed toothed whale 

 distribution in the Southern Ocean. He stated that most 

 toothed whales, except for sperm and killer whales, do not go 

 farther south than 60° S. Commerson's dolphin, known in 

 southern portions of South America, occasionally strays 

 south. The hourglass dolphin, dusky dolphin, and Peale's 

 dolphin occasionally range as far south as the northern edge 

 of the pack ice. However, Peale's dolphin is rarely found 

 away from its usual range of the southern tip of South 

 America, and the dusky dolphin does not usually go further 

 than 5 8° S. The other small odontocete whales occur 

 only rarely south of the Convergence (Brown et al., 1974). 



a. Sperm Whale 



The best known Antarctic toothed whale is the sperm 

 whale because of data acquired during commercial exploitation. 

 Sperm whales are thought to have widely dispersed feeding 

 stocks in lower latitudes (Mackintosh, 1972a) . Although 

 Best (1975) found little direct evidence to support separate 



