Reproduction results in parallel changes of oxidative stress and immunocompetence in a wild long-living mammal—edible dormouse <i>Glis glis</i>

Oxidative stress (OS) and impaired immune function (IF) have been proposed as key physiological costs of reproduction. The relationship between OS and IF remains unresolved, particularly in long-living iteroparous species. We studied physiological markers of maintenance (OS, IF markers) in lactating, post-lactating and non-lactating females of edible dormice-a long-living rodent. We predicted the OS balance and IF to be compromised by lactation, especially in older females expected to face stronger trade-offs between life functions. We found that the age predictor (body size) correlated negatively with white blood cell level (WBC), positively with neutrophils to lymphocytes ratio and had no effect on OS markers. Oxidative damage markers (reactive oxygen metabolites (ROMs); but not antioxidant capacity) and body size-adjusted WBC were the lowest in lactating, higher in post-lactating and the highest in non-lactating females. Body size/age did not affect this correlation suggesting a similar age-independent allocation strategy during reproduction in this species. The path analysis testing the causal relationship between ROMs and WBC revealed that IF is more likely to affect OS than <i>vice versa</i>. Our study indicates the trade-off between crucial life functions during reproduction and suggests that immunosuppression reduces the risk of OS; therefore, mitigating oxidative costs of reproduction.