THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 137 



are reviewed and a summary of information on the past and 

 present world populations is presented. Field counts of living sea 

 otters (omitting pups carried by mothers) furnish the information 

 on which this study of population and distribution is based. To 

 obtain a knowledge of population dynamics, studies of mortality, 

 reproduction, food habits, and movements of sea otters were also 

 undertaken. 



Modern 



ALASKA POPULATIONS 



The greatest population of sea otters in the world today is in 

 the central to outer Aleutian Islands (table 36). This is also the 

 area where repopulation of available habitat, from which the sea 

 otter was extirpated before 1911, is apparently occurring the most 

 rapidly. It is also the location where most of our studies were con- 

 centrated. 



Data were made available by individuals who visited or worked 

 in Alaska during the 1930's and 1940's. Additional data were ob- 

 tained, particularly after 1955, by observers who made extensive 

 aerial and surface surveys. During these studies, areas occupied 

 by sea otters as well as areas to which otters have not yet returned 

 were surveyed. 



The Aleutian Islands chain consists of five named groups of 

 islands from w^est to east (subgroups are in parentheses) : the 

 Near (Semichi Islands), Rat, Andreanof Islands (Delarof Islands), 

 the Islands of Four Mountains, and Fox Islands (Krenitzin Islands) 

 (see map, fig. 68). Important island groups which furnish suitable 

 sea otter habitat are separated from each other by passes up to 

 55 miles wide, hundreds of fathoms deep, and swept by swift tidal 

 currents. These wide passes appear to hinder seriously the move- 

 ments of otters from a heavily populated area to a neighboring 

 island group having vacant habitat. 



Today (1968), a sea otter ''population explosion" is occurring 

 in the Andreanof Islands. The early expansion of this population 

 was sketchily documented during the late 1930's and early 1940's. 

 More thorough observations were made in the 1950's and until 

 . 1965. A similar ''population explosion" in the Rat Islands ap- 

 \ parently reached a climax in the mid-1940's. The historical data 

 \ on these two populations are reviewed below and compared with 

 j modern findings. 



The locations in which sea otters survived the 1741-1911 period 



