THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 



65 



dives appeared to determine the duration of his. The mean duration 

 of food dives was 65 seconds and the extremes were 20 and 95 

 seconds. The majority of the dives (69 percent) lasted between 

 50 and 80 seconds (fig. 31). 



In generalizing on the duration of food dives in the usual for- 

 aging depths, between 10 and 25 m., it may be said that the adult 

 female usually stays beneath the surface for about 1 minute and 

 the adult male for about IV^ minutes. 



The number of dives in a feeding period varies. In 9 hours and 

 8 minutes when records were kept the mated pair spent 4 hours 

 and 45 minutes in feeding activity, making 87 dives in water ap- 

 proximately 23 m. deep. Nikolaev and Skalkin (1963) report ob- 

 servations of 63 dives in 1 hour and 18 dives in 12 minutes. Pre- 

 sumably these data were obtained from animals feeding in shallow 

 water. 



Duration of escape dives 



The sea otter, however, is capable of dives of long duration. This 

 was demonstrated when we pursued a female otter for 50 minutes 

 on 10 July 1960 in the Bering Sea off Unimak Island. During the 

 chase she made 13 dives averaging 120 seconds beneath the sur- 



40r 



30- 



UJ 



> 



39 % 



°20 



q: 



UJ 

 QQ 



30 % 



10 



18 % 



9% 



3% 



0 



20 35 50 65 80 



DURATION OF FOOD GATHERING DIVES IN SECONDS 



95 



Figure 31. — Duration of 87 timed food dives made by a mated pair of otters. 

 The water depth was 23 m. The male followed the female closely, both in 

 submerging and emerging. 



