106 



NORTH AMERICAN FAUNA 68 



That certain individual animals would learn to feed on pelagic 

 forms and thus divorce themselves from the necessity of remaining 

 in relatively shallow water is improbable. Observations indicate 

 that the sea otter subsists only on benthic organisms. Wide, deep 

 passes between islands, which prevent bottom feeding, appear to 

 act as a barrier to the spread of sea otter populations. (See Distri- 

 bution and Numbers.) 



Food Gathering 



Many observations indicate that the sea otter uses its f orepaws 

 primarily to gather food and that the tactile sense is important 

 in locating food organisms. A captive female with good eyesight 

 was offered food in a bucket about half full of turbid water. In 

 one instance the bucket contained about 200 small crabs (Pachy- 

 grapsus), 4 blue mussels (Mytilus edulis), and a number of peb- 

 bles of various sizes. The otter had eaten both organisms before 

 but showed a preference for mussels. When the bucket was pre- 

 sented to her, she immediately reached to the bottom with both 

 forepaws, her chin on the edge of the bucket, and within a few 

 seconds retrieved the four mussels. She made no attempt to place 

 her head in the bucket or to look into it. Thus, she demonstrated 

 a high reliance on her tactile sense in selecting the mussels from 

 among pebbles and crabs. 



Numerous observations of Susie, during the 6 years that she 

 lived at the Woodland Park Zoo, indicated that she relied heavily 

 on her tactile sense while retrieving food placed in her pool. She 

 was blind in her right eye when captured and blind in both eyes 

 for over a year before death. During this period of total blindness 

 she continued to find food and to select the most desired kinds, 

 using her paws to select it. I have observed several healthy wild 

 otters that were blind in one eye but have seen only one that was 

 apparently blind in both eyes. This animal was emaciated and 

 near death. Existence without sight among breakers in the harsh 

 coastal environment would probably be impossible even if food 

 could be found. 



Wild otters normally terminate feeding activities before dark 

 and do not begin morning feeding until after sunrise. Mothers 

 w^hich must provide for their young, however, may continue diving 

 for food after dark. I watched a mother diving one evening until 

 darkness prevented further observations. During the period 

 shortly before visibility was lost, the otter continued to bring food 

 items (mostly sea urchins) to the surface in the usual quantities. 



