THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 



11 



For this reason, observers often report the presence of sea otters 

 when they have actually seen river otters. To help in correct 

 identification of these two species, the following comparison of 

 diagnostic physical and behavioral characteristics is presented 

 (see also figs. 5 and 6) : 



Field observation 



Sea Otter 



1. Occurs in Alaska from Prince William Sound, along the Alaska Peninsula, 

 in the Aleutians, and near Monterey, Calif. Is currently extending its range 

 and should be looked for in Pacific coastal areas. 



2. Found along open-sea coast in salt water only. 



3. On surface usually swims belly up, forepaws on chest while paddling 

 with hind flippers. Floats high in water. 



4. Clumsy on land, seldom seen on shore except in isolated Alaskan areas. 



5. Eats while floating on back, never eats on shore. 



6. Sleeps (usually) in kelp beds or calm water while floating on its back 

 (fig. 7). 



7. Bears single young which is carried on the mother's chest as she swims 

 on her back. 



River Otter 



1. Occurs on rivers and along seacoasts in the United States, Canada, and 

 Alaska. Often swims several miles in salt water between islands. 



2. Found in salt or fresh water. 



3. On surface usually swims belly down, back nearly submerged. 



4. Agile and graceful on land, often seen on land. 



5. Brings food ashore to eat. 



6. Sleeps on land, usually, in dens, never while floating on its back. 



7. May have up to four young, does not carry them on chest while swim- 

 ming. 



Specimen Observation 

 Sea Otter 



1. Maximum weight 100 lb. 



2. Maximum length 58.25 in. 



3. Fur long and soft, guard hair delicate and sparse. 



4. Claws of forepaws short and retractile. 



5. Hind feet decidedly flipperlike and webbed to tips of toes. Pads visible 

 only at tips of toes (fig. 8) The fifth or outer digit is longest (fig. 9). 



6. Tail somewhat flattened and does not thicken markedly at base, less than 

 Vs of body length. 



7. Eyes are open at birth. 



8. Last upper molariform tooth broad and flattened, about % inch or more 

 in greatest width. 



9. Baculum of adult about 6 inches in length (fig. 10). 

 River Otter 



1. Maximum weight 30 lb. 



2. Maximum length 50 in. 



3. Guard hair coarse and dense, covering fur completely. 



4. Foreclaws long and not retractile. 



5. Hind feet webbed but not flipperlike. Pads cover much of palm and digits. 

 The fifth digit is not elongated. 



6. Tail nearly round in cross section and heavily thickened at base, more 

 than V2 of body length. 



