194 



NORTH AMERICAN FAUNA 68 



The Kanaga data indicate that this level may be maintained for 

 at least a 3-year period. The Amchitka data indicate that after the 

 initial population ''crash" a period of slow increase, or adjust- 

 ment, occurred (table 23). During the recovery period the popu- 

 lation approached a density of about 20 otters per square mile of 

 feeding habitat. That this is not an optimum population density is 

 indicated by the continued annual occurrence of heavy mortality 

 among juveniles and old adults (see Age Specific Mortality), by 

 comparatively small body size (see Body Measurements), by ex- 

 cessive dental attrition, and by the fact that by 1965 the population 

 had fallen to a density of 14 otters per square mile of habitat. 



Optimum population density in the Aleutian area, after a de- 

 pleted habitat has recovered from the damage caused by over- 

 utilization of food resources, may be postulated at about 10 to 15 

 otters per square mile of habitat. Table 38 shows predicted 

 populations in certain Alaska areas based on data now available. 

 More data are needed, however, to properly estimate optimum 

 population density. 



Geographic barriers 



Passes between areas of feeding habitat around islands, may 

 act to a varying degree as barriers to the spread of sea otter 

 populations. For example, Buldir, Semisopochnoi, and the Near 

 Islands were not repopulated for a number of years after the 

 islands nearest to them supported high populations. The 55 miles 

 of open water between Buldir and Kiska was an effective but not 

 a permanent barrier. A few otters reached Buldir from Kiska 

 betwen 1936 and 1961. Kiska was densely populated by 1959 and 

 perhaps before that, but not until the 1959-65 period were small 

 colonies established in the Near Islands, 65 miles west of Buldir. 



Table 38. — Present and projected sea otter populations in certain Alaska areas 



[Only the areas that have been most intensively studied are included. The projections of future 

 populations are based on the assumption that a population of about 10 to 15 otters per square 

 mile of feeding habitat may be supported] 



Area 



Square 

 miles of 

 habitat 



Projected total 

 number of 

 sea otters 



Present 

 population 

 estimate 



Near Islands 



Rat Islands 



Andreanof Islands 



326 

 293 

 766 

 89 

 88 

 570 

 200 

 1,000 

 900 

 700 



3,300- 5,000 

 3,000- 4,400 

 7,700-11,500 

 900- 1,300 

 900- 1,300 

 5,700- 8,500 

 2,000- 3,000 

 10,000-15,000 

 9,000-13,500 

 7,000-10,500 



27 



4,200 

 7,800 



Delarof Islands - 



Islands of the Four Mountains. 



930 

 0 

 25 

 55 



Fox Islands. 



Krenitzen. 



Unimak-Amak Islands 



4,000 

 1,600 

 2,700 



Sanak Island and Sandman Reefs,... 



Shumagin Islands. 



Total. 



4,932 



49,500-74,000 



21,337 



