FEEDING 



Loper i/aiA/ 



259 



Palate 



Bdleen 



Tone 



noue 

 Lci\er Jaw 



Figure 134. Diagrammatic sketch of the head of a Rorqual showing position of baleen and 



tongue. {Hentschel, 1937.) 



Thus a Humpback whale caught in the North Atlantic was found to have 

 six cormorants in its stomach, with a seventh stuck in its throat. Japanese 

 whalers, too, have more than once discovered cormorants in the stomachs 

 of Fin Whales. Bryde's Whale keeps to an almost exclusive diet of fish 

 (especially pilchard and anchovy) - and not surprisingly, since it lives 

 largely in tropical and sub-tropical waters where there is much less 

 plankton. Moreover, the hairs of its baleen plates are so coarse that it 

 could not function as an effective plankton strainer. Even sharks of up to 

 two feet in length have been found in the stomachs of Bryde's Whales, 

 and there is at least one known case of one of them swallowing fifteen 

 penguins which were themselves hunting for fish. Krill has been found, 

 however, in the stomachs of Bryde's W' hales caught olTthe Bonin Islands. 

 Obviously, enormous animals like whales cannot get hold of such small 

 fry as krill with ordinary teeth and jaws, and nature has therefore provided 

 them with a structure akin to a plankton net - a strainer through which 

 water can flow freely while krill itself is kept back. In all Mysticetes, this 

 strainer takes the form of horny whalebone or baleen plates, each less 

 than one-fifth of an inch thick. The plates are fringed along their inner 

 edges and descend like side-curtains in two rows from the upper jaw 

 (Fig. 134). The distance between any two plates is under half an inch, 

 and the plates curve slightly backwards, which gives more rigidity and 

 probably has the effect of letting the water flow out more smoothly, and 

 thus obviates unnecessary turbulence. 



