THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 237 



implantation and the gestation period has been determined to be 

 about 63 days (Cocks, 1881). 



The data of Hamilton and Eadie (1964) show conclusively that 

 the gestation period of the American river otter includes a period 

 of delayed implantation. The data of Liers (1951) appear to indi- 

 cate that this period may be variable. He recorded extremes of 

 9 months 18 days to 12 months 15 days in the total gestation period 

 of captive otters. 



Huggett and Widdas (1951) shov^ed that during certain phases 

 of prenatal growth the cube roots of fetal weights fall along a 

 straight line. They indicate that an adjustment can be made for 

 the period before the cube root of fetal weights begins to follow 

 a straight line. This adjustment, however, is minor and, in esti- 

 mating the period of implanted gestation in the sea otter, is 

 ignored on the graph (fig. 94). 



The weights of two young European otters that were presumably 



Figure 94. — Estimated period of implanted pregnancy. The periods are esti- 

 mated for the American river otter and sea otter on the assumption that 

 their fetal growth velocities are similar to that of the closely related 

 European river otter (see Huggett and Widdas, 1951). 



