Table 3. — Numbers of sea lions, Chignik district, 1956-57 

 determined from photos 



[* indicates visual estimate] 



Rookery and . 

 code number i' 



Adults Pups Total Adults Pups Total 



1956: 



Survey 1, July 26- Aug. 4 



1. Atkulik Island 12 12* 



2. Kak Island 97 97 



3. Cape Kumlik 10 1 



4. Kupreanof Point 0* 



5. Mitrofania Island 216 216 



6. Seal Cape 11 11* 



7. Spitz Island 40 40* 



8. Sutwik Island 733 5 738 



9. Ugaiushak Island 572 71 643 



Total 1,682 76 1,758 



1957— Con. 



Survey J, June 28 



2. Kak Island 150 150* 



4. Kupreanof Point 



5. Mitrofania Island 



7. Spitz Island 125 125* 



8. Sutwik Island 0* 



9. Ugaiushak Island ; 



Total 275 275 



1957; 



950 



950 



582 



582 



1/ Code numbers refer to map in figure IC. 



Diurnal Variations 



I3onnot (1928) stated that sea lions do most 

 of their feeding at night or early in the morn- 

 ing, and he recommended that any census 

 counts be made between 1000 in the morning 

 and 1500 or 1600 in the afternoon. 



Bonnot's recommendation was substantiated 

 by the Institute's studies on Chernabura Island 

 in 1958.* In one undisturbed control area, 

 designated as area I, visual censuses were 

 taken during established hours each day (table 

 7). On Saturdays and Sundays the counts were 

 not made at any definite time. Although counts 



'See footnote 1 on p.. 6, 



of pups remained stable at all hours, counts 

 of adults on the rocks were high from early 

 morning until afternoon. Toward evening and 

 after sunset when the sea lions were feeding, 

 counts were smaller. 



This diurnal cycle was modified by the surf. 

 If a plot is made of the height of ocean swell 

 and the average number of animals counted 

 during the season, an inverse relation appears 

 (fig. 5). Apparently on stormy days, sea lions 

 on Chernabura Island preferred to go to sea 

 and ride out heavy waves in the water. 



No systematic studies of these behavior 

 patterns were made because good aerial pic- 

 tures depend on moderate wind and calm sea. 



