Ovarian characteristics and reproductive performance of reindeer, Rangifer tarandus.

A total of 301 female reindeer of various ages was shot on South Georgia in all months of the year to study seasonal and age-related changes in ovarian structures, and to undertake an intraspecific comparison with North American caribou. Ovarian weights and follicle numbers did not change in reindeer calves, and it is concluded that the South Georgia population do not attain physiological puberty in their first year. Compared with caribou, reindeer showed an earlier onset of ovarian activity, and had twice as many follicles greater than 2 mm diameter and secondary corpora lutea. The relationship between luteal scars and age was significant (P less than 0.001), despite an overcount of scars relative to age in some individuals, and indicated a fecundity rate of 0.93. The left and right ovaries of reindeer were equally productive. It remains unclear whether the differences in reproductive performance between reindeer and caribou are of genetic origin.