Data from: Sex-specific effects of early-life adversity on adult fitness in a wild mammal

Early-life adversity influences adult fitness across vertebrate species.
In polygynous systems with intense intrasexual competition, males may be
more sensitive to conditions experienced during development. However, the
importance of different aspects of the early-life environment and how
their effects differ between the sexes remains poorly understood. Here, we
used a long-term study of wild Soay sheep to characterise the early-life
environment in terms of weather, infection risk, resource competition and
maternal investment, and test the hypothesis that males are more
vulnerable to early adversity. Birth weight, reflective of maternal
investment and conditions during gestation, positively predicted lifetime
breeding success in both sexes, suggesting a classic ‘silver spoon’
effect, though the effects were stronger in males. Males that experienced
increased resource competition in their first year had lower lifetime
breeding success, suggesting lasting negative consequences of nutritional
stress, but there was no association in females. In contrast, challenging
weather in the first winter of life was associated with stronger viability
selection, with males surviving these harsh conditions having higher adult
fitness. Our findings further evidence the important long-term fitness
consequences of early-life adversity in wild vertebrates, demonstrating
distinct aspects of the early environment may shape fitness in different
and sex-specific ways.