66 



NORTH AMERICAN FAUNA 68 



face. The longest dive lasted for 250 seconds (4.2 minutes) and 

 the shortest 30 seconds. The last timed dive of 205 seconds 

 indicated that the animal had not become exhausted and we 

 abandoned the chase as futile. Barabash-Nikiforov (1947) says 

 that "the longest time that the sea otter can submerge is not more 

 than 6 minutes." My conclusion is that the maximum duration of 

 a dive is probably less than 6 minutes. 



Depth of diving and distance from shore 



The maximum depth to v^hich a sea otter may descend to gather 

 benthic food organisms is not definitely knov^n. Consideration of 

 the historical record along v^ith modern observations and data, 

 however, indicate certain tentative conclusions. 



The greatest diving depth I find in the historical record is 

 quoted from Chase Littlejohn, a sea otter hunter of the 19th 

 century. He said 'There is a [place] . . . about 50 fathoms deep 

 where they go to the depth of the water to feed" (Hall, 1945). 

 Other otter hunters indicate lesser diving depths. Snow (1910, 

 p. 281) stated that the sea otter appears to prefer to get its food 

 at depths of 10-25 fathoms. 



Captain C. L. Hooper (1897) studied the sea otter and problems 

 of conserving it in Alaska during the latter part of the 19th 

 century. It was his conclusion that "banks of 30 fathoms of water 

 are its feeding grounds." Further, he concluded — 



that the principal parts of the present sea otter grounds are already within 

 the territorial waters of the United States. . . . suitable regulations by the 

 United States Government, properly enforced, will furnish ample protection 

 for the sea otter, as not enough can be taken outside of these limits to en- 

 courage hunting to any extent. 



This statement implies that otters seldom ventured to depths 

 greater than those found relatively near shore. 



Modem observations tend to confirm the early sea otter hunters' 

 information, except that in certain areas where shallow water is 

 found far from land sea otters appear to find suitable feeding 

 grounds beyond the 3-mile limit. 



During seven seasons (April through August, 1957-63) A. C. 

 Hartt and B. F. Jones recorded all sea otters sighted beyond 3 

 miles from shore. Their primary mission was offshore fisheries 

 investigations during which their ships operated near various 

 Aleutian islands, in the passes between them, and as far as 200 

 miles from land in the North Pacific and Bering Sea. 



Their observations of otters over deep water (table 10) are of 

 interest, because in each case the otters were near areas where 



