THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 15 



Figure 8. — Plantar surface of the left hind foot of an adult male sea otter. 

 The outer (fifth) digit is longest, a condition not found in other mam- 

 mals. This adaptation increases efficiency of propulsion by the foot when 

 the otter swims on its back. Pad development at the tips of the toes is 

 minimal. The vestigial pads near the center of the foot are not visible on 

 some individuals. (KWK 62-23-26) 



or abdomen. Thus, all animals carrying young are recognized as 

 females. Large juveniles, still with their mothers, may approach 

 an adult male and romp with him. Thus care is necessary during 

 observation to differentiate between the mother and a ''visiting" 

 male. 



It was shown that the adult male averages larger than the 

 female (see Body Measurements) but because of overlap, size 

 alone is not useful in recognition of the sexes. 



The head and neck are heavier and more muscular in appearance 

 in the adult male than in the female. If a mated pair is observed, 

 this difference is apparent. Because of individual variation, how- 

 ever, much observation and field experience is necessary before 

 this relatively slight difference becomes a useful character in the 

 recognition of sex. 



In its behavior, the male sea otter is relatively bold. If a human 

 approaches a group of males and females hauled out near each 



