Early maternal investment and growth in reindeer

Abstract

I studied whether females in a herd of semidomesticated reindeer (Rangifer tarandus) in Finland invest more heavily in male than in female offspring and whether the mother's body size and condition have different effects on growth rates of male and female offspring. The results did not provide evidence of different preweaning investment in male and female offspring. Proportional mass loss of breeding females during calving was greater when the calf was male than when it was female, but change in mass between consecutive autumns did not depend on the sex of the calf. In general, the growth of male and female calves depended in approximately similar fashion on maternal characteristics, but amongst the male calves only, the growth rate from birth until the following November depended on the mother's change in mass the previous winter. Mass loss of parturient females was inversely related to mass loss during pregnancy. Females that experienced heavy mass loss from November until postcalving gained the most mass before the following November. Winter food supplementation probably led to large body masses and a low mortality rate of calves and might have masked differences in reproductive costs associated with producing male and female calves.