THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 229 



Counts of otters were made primarily at Amchitka Island, from 

 beaches and cliff tops and during dory trips through inshore 

 waters. Binoculars (7X50) and a telescope (50 power) were used 

 for observation. 



DEFINITION OF TERMS 



Implanted pregnancy observations are based on visible swellings 

 of the uterine horn, presence of a corpus luteum, and recovery of 

 the conceptus. Unimplanted pregnancy observations are based on 

 the presence of a corpus luteum not accompanied by swelling of the 

 uterine horn. Sinha et al. (1966) demonstrated that when a corpus 

 luteum is present and no uterine swelling is visible a blastocyst 

 may be recovered from the uterine horn. Multiparous animals were 

 separated from nulliparous and primiparous animals by the thick- 

 ened appearance of the uterine horns which, after having held a 

 conceptus, do not regain the smooth, firm texture of the nulliparous 

 uterine horn. 



Tracts were classified as nonpregnant when no corpus luteum 

 was present. A female was considered to be post partum if one or 

 more of the following conditions was observed: (1) lactation, (2) 

 presence of a pup, (3) presence of a corpus albicans, (4) presence 

 of a placental (uterine) scar. Because it appears that the young sea 

 otter remains with its mother for about a year, certain evidence of 

 a post partum condition may be obscure by the time the pup and 

 mother part. The placental scar may virtually disappear and the 

 corpus albicans may be reduced in a female accompanied by a large 

 pup. One lactating female, whose pup was either recently lost or 

 was not seen by the hunters, showed no placental scar and the 

 corpus albicans was very small. 



Classification of ovaries as estrous, proestrous, and anestrous, 

 based on macroscopic examination of sectioned ovaries, are con- 

 sidered briefly in the following discussion. The objective of this 

 study is to present a review of the natural history of reproduction. 



AGE AT SEXUAL MATURITY 



Sufficient data are not available to fix with certainty the age at 

 sexual maturity. Some information was obtained from a juvenile 

 female (approximately 1 year old), weighing about 24 lb. 

 (10. 9 kg.), that was tagged (EL 556, table 39) on 22 March 1962. 

 On 18 March 1963, when this animal was shot 2.5 miles from the 

 place of marking it weighed 33 lb. The dentition was that of a 

 young adult, but the reproductive tract was decidedly immature. 



