Data from: Maternal longevity and offspring sex in wild ungulates

In species with sexual size dimorphism, offspring of the larger sex
usually have greater energy requirements and may lead to greater fitness
costs for parents. The effects of offspring sex on maternal longevity,
however, have only been tested in humans. Human studies produced mixed
results and considerable debate mainly due to the difficulty of
distinguishing the effects of sexual dimorphism from sociocultural
factors. To advance this debate, we examined how the relative number of
sons influenced maternal longevity in four species of free-living
ungulates (Soay sheep Ovis aries; bighorn sheep, Ovis canadensis; red
deer, Cervus elaphus; mountain goat, Oreamnos americanus), with high
male-biased sexual size dimorphism but without complicating sociocultural
variables. We found no evidence for a higher cumulative cost of sons than
of daughters on maternal longevity. For a given number of offspring, most
females with many sons in all four populations lived longer than females
with few sons. The higher cost of sons over daughters on maternal lifespan
reported by some human studies may be the exception rather than the rule
in long-lived iteroparous species.