280 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 



in correspondence in 1957, writes that a subadult female in the 

 Seattle Zoo is very dexterous. It uses its front digits almost like 

 fingers in grooming and feeding operations.) 



It is well known that the molariform teeth have been greatly 

 modified for a special diet, and have departed strikingly from 

 the mustelid type. Instead of the teeth having a shearing func- 

 tion, they are used for crushing, and have taken a bunodont 

 form. 



A most interesting feature of the sea otter dentition is the 

 prevalence of cavities in the molariform teeth. Among the more 

 or less fragmentary skulls and jaws found in Aleut village sites, 

 a considerable percentage of the teeth had cavities, large and 

 small. E. M. Fisher (1941) has given a detailed discussion of 

 this and other features of the sea otter's dentition, and she 

 intimates that rather active evolutionary changes may be taking 

 place. She suggests that the difference in diet between the 

 southern and northern sea otter may account for the greater 

 prevalence of cavities in the teeth of the northern form. As in- 

 terpreted by Fisher, the dental formula of the adult would be 

 I 1,2,3-Cl-Pm 2,3,4-Ml 

 I 1,2 -Cl-Pm 2,3,4-Ml,2 ' 



The sea otter is generally dark brown, with considerable varia- 

 tion, although this variation may be clue to age. Some old ani- 

 mals, as typified by the old male obtained by the writer at Ogliuga 

 Island, are a dull, dark brown, becoming black on legs, but with 

 a pale-brown head and neck — this pale coloration extends down 

 on the chest, where it becomes almost straw-colored. The under 

 side of the tail is paler than the body. White hairs are sprinkled 

 throughout the pelage. In most of the darker animals these 

 silvery hairs become more conspicuous. The younger adults are 

 much darker, often blackish, with fine, lustrous fur. 



The young pups are a very light brown. In every case, from 

 the pup to the grizzled old male, the head and neck is paler than 

 the body, and this difference is accentuated in the very old ones. 



General Habits 



There is a voluminous literature on the habits of the sea otter, 

 much of it largely repetition of what was reported by the earliest 

 observers, including Steller. Only in the last few years have we 

 begun to study the sea otter in any great detail, and there is 

 much to learn. Therefore, I will not attempt to give a compre- 

 hensive life history of this interesting mammal. 



Of chief interest to the biologist is the fact that this member of 

 the weasel family has resorted to a marine environment and has 



