Effect of body size, body mass, and body condition on reproduction of female South African fur seals (Arctocephalus pusillus) in Namibia

The relationships between female reproductive parameters (fertility, pregna ncy, and lactation status) and body mass, body condition, and body length i n South African fur seals (Arctocephalus pusillus) were investigated over 4 years. Ovulation rate in every year was 100% despite interannual differenc es in female body condition index (BCI). The overall pregnancy rate was 79% . The proportion of pregnant females was related to ECT but not to body mas s or body length. In good years, BCI decreased through the first part of th e reproductive cycle to a minimum at implantation and increased again throu gh pregnancy. In 1989, BCI declined over the whole reproductive cycle, and there was a higher proportion of nonpregnant females and failures of lactat ion. Thus, poor nutritional conditions may affect reproductive success thro ugh failure to rear a pup, and pup production the following year may also b e reduced. This lower rate of pregnancy is partly explained by an increase in the incidence of spontaneous abortions, but other parameters such as a l ower implantation rate are also likely to be involved.