Data from: Survival costs of reproduction are mediated by parasite infection in wild Soay sheep

A trade-off between current and future fitness potentially explains
variation in life-history strategies. A proposed mechanism behind this is
parasite-mediated reproductive costs: individuals that allocate more
resources to reproduction have fewer to allocate to defence against
parasites, reducing future fitness. We examined how reproduction
influenced faecal egg counts (FEC) of strongyle nematodes using data
collected between 1989-2008 from a wild population of Soay sheep in the
St. Kilda archipelago, Scotland (741 individuals). Increased reproduction
was associated with increased FEC during the lambing season: females that
gave birth, and particularly those that weaned a lamb, had higher FEC than
females that failed to reproduce. Structural equation modelling revealed
future reproductive costs: a positive effect of reproduction on spring FEC
and a negative effect on summer body weight were negatively associated
with overwinter survival. Overall, we provide evidence that parasite
resistance and body weight are important mediators of survival costs of
reproduction.