THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 121 



fracturing the test. Then, with the aid of paws and teeth, the otter 

 is able to open the test and with the lower incisors and tongue to 

 scoop out the exposed viscera and gonads (Hildebrand, 1954). 

 Large urchins may also be opened primarily with the paws. The 

 top of the urchin is cradled against the palm of one paw while 

 the digits and palm of the other exert pressure on the test sur- 

 rounding the urchin's oral opening, crushing it inward. The 

 urchin may be rotated to facilitate application of pressure. When 

 the test is sufficiently weakened the teeth are used to remove the 

 broken test so that the contents may be scooped out. The empty 

 test may be tossed aside with the paws or dropped on the chest or 

 belly while another item is eaten. 



Sea cucumbers appear to be of minor importance in the diet of 

 the sea otter, they appeared in only 26 stomachs. They are tough 

 and showed relatively little multilation from chewing (fig. 65). 

 We did not give them to captive otters but Shidlovskaya (1947) 

 says that they were eaten reluctantly by her captives. 



Tunicates, having a tough leathery covering, do not appear to 

 be an important food. A few individuals were in 11 stomachs. 



Fish, particularly the globefish (Cyclopterichthys glaber), con- 

 tributed the greatest food volume (50 percent of all food volumes 

 combined) among stomachs taken at Amchitka. It is evident that 

 this food source, along with mollusks, is of major importance. 



The identification of fish species eaten is sometimes difficult be- 

 cause sea otters often discard diagnostic bony plates from the 

 heads of fish. Also, the bones that are swallowed may be severely 

 crushed during mastication. The variety of fish eaten is not large 

 and a series of specimens was accumulated during stomach ex- 

 aminations that enabled us to identify most fish remains. 



The fish taken are usually bottom-inhabiting forms and are 

 somewhat sedentary or sluggish. The red Irish lord (fig. 64) and 

 globefish, both sluggish species, occurred in 75 percent of the 

 stomachs containing fish. Information obtained from hundreds of 

 trammel net hauls at Amchitka, as well as data from the stomachs 

 of harbor seals taken there, indicate, however, that the rock 

 greenling and Atka mackerel may be more abundant than the red 

 Irish lord or globefish. However, they are more active than these 

 two species and possibly for this reason are less frequently cap- 

 tured by the otters. 



The sea otter does not appear to be well adapted to the capture 

 or consumption of fish. The dentition is very unlike that of seals 

 and porpoises. All marine mammals that eat fish, except the sea 

 otter, capture them with their teeth and swallow them without 



