Allometry and variability of resource allocation to reproduction in a wild reindeer population

Abstract

The differential allocation of energy to either reproduction or survival represents a major conflict with important implications for patterns of life history. Here, we explore how covariation between maternal body weight and fetal weight vary according to fetal sex in a wild reindeer (Rangifer tarandus) population during two contrasting years. Maternal weights differed during the 2 years, probably because of a difference in population density. We could not detect any change in the allocation to reproduction depending on female phenotypic distribution. Male fetuses were heavier than female fetuses, with the same relative dimorphism in both years. There was no support for a correlation between the sex of the fetus carried by a female and her weight. Our results suggest that the level of resource allocation to reproduction during the prenatal period is strongly determined by female body weight and the allometric relationship between body weight and metabolic rate. We discuss the consequences of our results for population dynamics. We call for an integration of inter- and intraspecific allometric approaches to better understand constraints and variation in life-history traits. Key words: allometry, body weight, prenatal resource allocation, Rangifer, reindeer, sex bias. [Behav Ecol]