THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 251 





1937 



1 



• SU 





1939 



6 



— SU, F W 





1940 



2 



> w,s,su 





1947 



6 



F (4M-- BEACH ) 



o 



1948 



100+ 



W,S 



< 



1949 



124 



W,S 



> 











1950 



20 



W,S 



O 



1951 





"losses heavy" 



O 



1952 





"losses light" 



Of 



< 



1953 



74 



w, s 





1956 



54 



su 





1957 



31 



F 





1959 



84 



w,s 





196 2 



106 



w,s 





1963 



36+ 



s 









1 1 1 1 1 1 



0 20 40 60 80 100 120 130 



NUMBER OF SEA OTTERS 



Figure 95. — The counts (solid line) and estimates (broken line) of dead sea 

 otters on Amchitka beaches indicate the order of magnitude of annual 

 mortality. Except for the counts of 1949, 1959, and 1962, the figures are 

 only roughly comparable. The information was obtained from unpublished 

 reports in Fish and Wildlife Service files: 1937, C. L. Loy and 0. A. Friden; 

 1939, C. L. Loy; 1940, J. B. Mangan and G. Ritter; 1947, V. B. Scheffer 

 and K. W. Kenyon; 1948, E. C. Hanson; 1949, 1950, 1953, R. D. Jones; 

 1956, 1957, 1959, 1962, K. W. Kenyon; 1963, J. E. Burdick; and from 

 Rausch (1953). The season of observation is indicated as follows: W— 

 winter; S=spring; SU=summer; and F=fall. In no case were all beaches 

 searched regularly. Counts were obtained mainly on the southeastern half 

 of the island. This data is useful only in illustrating the relative magnitude 

 of mortality in different years. 



tideline and die on shore. Dead sea otters float and if they die in 

 the water they usually wash ashore. Thus a high percentage of 

 those that die in study areas may be found if beaches are searched 

 systematically and frequently. 



To study annual mortality as a factor in population dynamics, 

 and to ascertain its magnitude and understand its causes, I made 

 an effort to gather comparable mortality data during five trips to 

 Amchitka. 



Methods of study 



Certain beaches on the eastern half of Amchitka were searched 

 systematically. Observations are available for each month of the 

 year. Most dead otters were on or near favorite hauling-out 



