Uterine Horn of Conception and 

 Fetal Sex Ratio 



In the fur seal the first conception seems 

 to occur randomly in either side of the bi- 

 cornuate uterus, then alternately between horns 

 thereafter. For example, 51 percent of 5,868 

 pregnant and post-parturient females taken 

 since 1958 had conceived in the left uterine 

 horn and 49 percent in the right. Forty-eight 

 percent of 140 pregnant seals taken in 1969 

 had conceived in the left uterine horn. In 

 addition, 47 percent of the left and 53 percent 

 of the right uterine horns of 19 primiparous 

 females had fetuses. 



The fetal sex ratio in fur seals is about equal. 

 In 1969, 55 percent of 140 fetuses were males 

 and 45 percent were females. Since 1958 we 

 have examined 5,117 fetuses, of which 49 



percent were males and 51 percent were fe- 

 males. 



Feeding Habits 



Research on the feeding habits of fur seals 

 since 1958 has shown that these animals con- 

 sume a wide variety of fish and cephalopods 

 throughout their range in the eastern North 

 Pacific Ocean and eastern Bering Sea. Fur 

 seals feed mainly from dusk to dawn on readily 

 available food, mostly fishes and squids near the 

 surface. 



Of 333 seal stomachs collected in 1969, 190 

 (57 percent) contained food (table 44). Most 

 (92.3 percent) of the total food volume was 

 contributed by four species or groups: north- 

 ern anchovy, Engraulis mordax; rockfish, Se- 

 bastodes spp.; capelin, Mallotus villosus; and 



Table 44. --Stomach contents of fur seals collected pelagically by the United States off Washington, 6 February to 29 March 1969.L' 



1/ T=trace (<5 cc. ). Trace counts are included in frequency counts. 



41 



