108 



NORTH AMERICAN FAUNA 68 



It would appear that under usual circumstances the sea otter 

 does not use its teeth under water. On many occasions I have seen 

 sea otters come to the surface clasping living fish to their chests 

 with their forepaws. After surfacing, each otter grasped the fish's 

 head in its jaws and killed it, suggesting that the teeth are not 

 used to kill fish beneath the surface. 



That otters may use their teeth beneath the surface when 

 necessary to obtain food was demonstrated at Amchitka. In Con- 

 stantine Harbor the otters apparently learned that our net floats 

 marked an abundant supply of fish. We often saw an otter on the 

 surface, eating, near the floats. When we pulled the nets, we found 

 fish that the animals were unable to remove but which they had 

 partly eaten underwater. Usually about half the fish was left, but 

 occasionally only the head and pectoral girdle remained. The fish 

 were not bitten off cleanly; they were chewed, leaving strips of 

 skin and tooth-marked shredded flesh attached to the entangled 

 portion. The frequency with which we saw otters eating fish on 

 the surface near the nets indicated that they were able to remove 

 a considerable number. Rarely did otters become entangled in the 

 nets and drown. 



The stomach of one adult male contained a number of large clam 

 siphons. The siphons, with adhering fragments of mantle and 

 muscle tissue, appeared to have been ripped from the clams by the 

 otter's paws or teeth. Visceral material from these clams was 

 lacking in the stomach. Presumably the siphons protruded from 

 the sea's floor and the remainder of the clam was not dug out. 



Fisher (1939) postulated that the sea otter used either a rock 

 or its canine teeth to remove abalones from the bottom. Cox 

 (1962) presents convincing evidence that the sea otter uses a 

 rock to break the abalone shell; that the otter then removes the 

 viscera and, after the abalone dies and releases its hold on the rock 

 bottom, brings it to the surface where it eats the muscle from the 

 remainder of the shell. The behavior of a captive otter, which 

 persistently pounded a rock against an underwater drain cover 

 until it was able to damage the fastening and remove it (Kenyon, 

 1959), lends strong support to the use of a rock rather than the 

 teeth in obtaining abalones. The canine teeth are probably not of 

 sufficient strength to remove any but small abalones from the 

 bottom. 



A unique habit related to feeding in the sea otter, that of pound- 

 ing hard-shelled mollusks against a stone or other mollusk held on 

 the chest, has been given much attention, most recently by Hall 

 and Schaller (1964). Although this habit is frequently observed 



