THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 85 



Figure 46. — A captive otter pounded herring (Cliipea) against the cement 

 edge of her pool. The otter did not particularly relish this species as food, 

 and the pounding behavior appeared to denote frustration when more ap- 

 petizing food was not available. The irregular surface of the pool edge 

 shown was produced when the otter pounded this area with a rock, cracking 

 away the finishing layer. Rock pounding behavior appeared to express 

 frustration when food was not available in the pool. (KWK 61-10-27) 



frustration behavior. Also, I agree with the statement of Hall 

 (1965) that the pounding behavior in the sea otter is — 



but a behavioural adaptation that has no special relevance to the evolution of 

 the sort of intelligent, anticipatory skills which are most highly developed 

 in man and which he uses for the manufacture of a standard set of tools to 

 be kept in store and used on different occasions for various purposes. 



Thus, tool-using behavior in the sea otter might be likened to 

 the use of gravity by gulls and ravens. These birds commonly 



