Data from: Relative costs of offspring sex and offspring survival in a polygynous mammal

Costs of reproduction are expected to be ubiquitous in wild animal
populations and understanding the drivers of variation in these costs is
an important aspect of life-history evolution theory. We use a 43 year
dataset from a wild population of red deer to examine the relative
importance of two factors that influence the costs of reproduction to
mothers, and to test whether these costs vary with changing ecological
conditions. Like previous studies, our analyses indicate fitness costs of
lactation: mothers whose calves survived the summer subsequently showed
lower survival and fecundity than those whose calves died soon after
birth, accounting for 5% and 14% of the variation in mothers'
survival and fecundity, respectively. The production of a male calf
depressed maternal survival and fecundity more than production of a
female, but accounted for less than 1% of the variation in either fitness
component. There was no evidence for any change in the effect of calf
survival or sex with increasing population density.