110 



NORTH AMERICAN FAUNA 68 



What Food is Eaten 



The food of the sea otter consists predominantly of benthic in- 

 vertebrates and fish. At Amchitka Island fish predominate (50 

 percent by volume), mollusks are second in importance, and 

 echinoderms (mostly sea urchins) third (table 11). In other areas, 

 mollusks and echinoderms are found to predominate. 



That the feeding habits of the sea otter vary in different areas, 

 in accordance with the abundance of food organisms, is indicated 

 by the statements of Snow (1910), who claimed to have examined 

 hundreds of stomachs. He stated that he did not find clams among 

 the food species eaten by the sea otter and that — 



I have never noticed any traces of the shells of clams, or limpets, or mussels 

 in the stomachs I have examined, but found as a rule, the remains of crabs, 

 sea urchins, sea-squirts, and what looked like fish spawn. 



He also said that he very seldom found any remains of "ordinary 

 fish, the bones of which would immediately prove its presence." 

 He adds that the sea otter ''finds no difl^iculty in chewing up good- 

 sized crabs, which judging from the contents of the many stomachs 

 I have opened and examined, appear to be its chief food." Mr. 

 H. P. Hansen, a king crab (Paralithodes platypus) fisherman told 

 me (1964) that in the Andreanof Islands he ''often sees sea otters 

 eating king crabs, sometimes quite large ones." 



Although a large variety of organisms is eaten, individual otters 

 appear to have certain food preferences. "Individual sea otters 

 often prefer a certain food in the assortment of food characteristic 

 to them" (Barabash-Nikiforov, 1947). Some adult males at Am- 

 chitka subsist primarily on fish and rarely eat sea urchins. In 

 general, at Amchitka it appears that the otters fall into two 

 groups — those eating mostly fish and those eating mostly inverte- 

 brates. The fish eaters, as would be expected, show a higher degree 

 of infestation with certain parasites (principally T. decipiens) 



Table 11. — Volume and classification of food found in 309 sea otter stomachs 

 from Amchitka Island, Alaska 



[Only stomachs containing food' are considered. The samples include 107 stomachs collected in 

 January and February 1962, 20 stomachs collected in October 1962, and 182 stomachs collected 

 in March and April 1963] 



Food item 





Total volume 

 (milliliters) 



Percent of 

 total volume 



Annelid worms 





929 



1 



Crabs, shrimp, etc. „_ - - 



Mollusks 





467 

 34,895 



<1 

 37 



Echinoderms (mostly sea urchins) 





10,020 



11 



Tunicates — . 



Vertebrates (fish) 





363 

 46,518 



<1 

 50 



