pregnancy rates. They are also used to deter- 

 mine if the distribution of female seals differs 

 according to reproductive condition. 



Reproductive Condition 



The youngest pregnant female collected in 

 1966 was a primiparous 4-year-old (1.5 per- 

 cent of the 4-year-olds collected). Four multi- 

 parous 5-year-olds (6 percent of the 5-year- 

 olds collected) were taken. These five females 

 conceived at age 3 and produced or would have 

 produced pups at age 4. Of the 5-year-old 

 fennales taken, 21.2 percent were primiparous. 



The reproductive conditions of 428 fennales 

 collected off California in 1966 are given in 

 table C-14. 



Pregnancy Rate 



The number of female seals (and percentage 

 pregnant) taken in the eastern Pacific from 

 1958 to 1966 is shown in table 50; those taken 

 off California in 1966 are listed by month in 

 table C-15. One- and two-year-old females 

 were not included because none had been 

 pregnant. Between ages 7 and 15, there was 

 less than a 9-percent difference in the preg- 

 nancy rate of the total seals in an age class. 

 The percentage of pregnant females taken 

 during their productive years (ages 6-26) from 

 1958 to 1966 ranged from 73.4 in 1965 to 

 86.0 in 1963. In 1965 seals were collected from 

 April to June off California and Washington; 

 in 1963 they were collected in the Bering Sea 

 from July to September. 



Uterine Horn of Conception, Twinning, and 

 Fetal Sex Ratio 



The uterus of the fur seal is bicornuate, 

 and the gestation period is nearly a year. 

 Normally, conception alternates from one horn 

 to the other; however, both ovaries may 

 ovulate and a conceptus may develop in each 

 uterine horn simultaneously when neither horn 

 has supported a full-term fetus. Of 4,604 

 pregnant females collected at sea since 1958, 

 6 carried twins, 2 sets of which were in 

 separate horns. Arseniev reported twin 

 fetuses in separate uterine horns of a seal 

 collected in the Sea of Japan in 1964. 



There is no record of both twins surviving 

 until weaned. Peterson and Reeder (1966) ob- 

 served the birth of three pairs of twins on the 

 Pribilof Islands; in each case, at least one died. 



Only 0.1 percent of the pregnant seals col- 

 lected at sea since 1958 were carrying twin 

 fetuses. 



^°V. A. Arseniev. Report on U.S.S.R. fur seal in- 

 vestigations in 1964. All-Union Research Institute of 

 Marine Fisheries and Oceanography (VNIRO), Moscow, 

 101 pp. [Processed.] 



Pregnancy occurs in the left and right uterine 

 horn with about equal frequency. Of 5,281 

 pregnant and postparturient females, 51 per- 

 cent had conceived in the left uterine horn 

 (1958-66). 



The sex; ratio among fetuses is also about 

 equal. Of 4,592 fetuses examined since 1958, 

 5 1 percent were fennales and 49 percent were 

 males. 



ATTACHED ORGANISMS (COMMENSALS) 



Algae and gooseneck barnacles attached 

 to the guard hairs of seals were noted by 

 Scheffer (1962), who reported several hundred 

 barnacles on one seal. Since 1958, when the 

 current pelagic research program began, algae 

 and gooseneck barnacles have been observed 

 on seals at various times of the year through- 

 out their range. Algae that have been identified 

 from samples found on fur seals are Ectocarpus 

 sp. (Scheffer, 1962; Fiscus and Kajimura, 1965) 

 and Erythrocladia sp. (Scheffer, 1962). Three 

 species of gooseneck barnacles have been 

 identified: Lepas anatifera and L. pectinata 

 pacifica (Fiscus and Kajimura, 1965i 1967), 

 and L. hi Hi (Scheffer, 1962). 



No attempt was made to record all observa- 

 tions until 1964, when 98 of 343 fur seals col- 

 lected between 19 May and 1 June off Cali- 

 fornia, Oregon, and Washington were examined. 

 Algae were attached to the guard hairs of 21 

 seals, and gooseneck barnacles to 6 seals 

 (Fiscus and Kajimura, 1965). In 1965, all fur 

 seals taken off California from April through 

 June were exannined for algae and barnacles 

 (Fiscus and Kajimura, 1967). Exanninations 

 were resumed off California in 1966 from 

 January through March, completing a survey 

 during the time (January to June) when the 

 largest numbers of seals are found on this 

 wintering ground. Algae were found on 17.4 

 percent of the seals collected and barnacles 

 on 14.0 percent (table 51). Algae grew most 

 frequently on the throat, nape, and back. The 

 extent of algal growth varied from a few spots 

 to almost complete coverage of the haired part 

 of the body. Gooseneck barnacles were most 

 frequently attached to guard hairs on the ear 

 pinna, nape, and back, although they have been 

 found on most parts of the body, except for 

 hairless skin. Gooseneck barnacles collected 

 in 1965 and 1966 varied in capitulum size 

 from 1 to 15 mm.; 42 were counted on one seal. 

 In 1966, Lepas pectinata pacifica was found on 

 eight seals, and Lepas sp. on one seal. 



FOOD 



Fur seals feed mainly on fish and cephalopods 

 throughout their range in the eastern North 

 Pacific Ocean and Bering Sea. A report on the 

 food and feeding habits of fur seals was given 



61 



