Stressful conditions experienced by individuals during their early development have long-term consequences on various life-history traits such as survival until first reproduction. Oxidative stress has been shown to affect various fitness-related traits and to influence key evolutionary trade-offs but whether an individual's ability to resist oxidative stress in early life affects its survival has rarely been tested. In the present study, we used four years of data obtained from a free-living great tit population (Parus major; n ¼ 1658 offspring) to test whether pre-fledging resistance to oxidative stress, measured as erythrocyte resistance to oxidative stress and oxidative damage to lipids, predicted fledging success and local recruitment. Fledging success and local recruitment, both major correlates of survival, were primarily influenced by offspring body mass prior to fledging. We found that prefledging erythrocyte resistance to oxidative stress predicted fledging success, suggesting that individual resistance to oxidative stress is related to shortterm survival. However, local recruitment was not influenced by pre-fledging erythrocyte resistance to oxidative stress or oxidative damage. Our results suggest that an individual ability to resist oxidative stress at the offspring stage predicts short-term survival but does not influence survival later in life.

Early-life trade-offs faced by developing offspring can have long-term consequences for their future fitness. Young offspring use begging displays to solicit resources from their parents and have been selected to grow fast to maximize survival. However, growth and begging behaviour are generally traded off against self-maintenance. Oxidative stress, a physiological mediator of life-history trade-offs, may play a major role in this trade-off by constraining, or being costly to, growth and begging behaviour. Yet, despite implications for the evolution of life-history strategies and parent-offspring conflicts, the interplay between growth, begging behaviour and resistance to oxidative stress remains to be investigated. We experimentally challenged wild great tit (Parus major) offspring by infesting nests with a common ectoparasite, the hen flea (Ceratophyllus gallinae), and simultaneously tested for compensating effects of increased vitamin E availability, a common dietary antioxidant. We further quantified the experimental treatment effects on offspring growth, begging intensity and oxidative stress. Flea-infested nestlings of both sexes showed reduced body mass during the first half of the nestling phase, but this effect vanished short before fledging. Begging intensity and oxidative stress of both sexes were unaffected by both experimental treatments. Feeding rates were not affected by the experimental treatments, but parents of flea-infested nests fed nestlings with a higher proportion of caterpillars, the main source of antioxidants. Additionally, female nestlings begged significantly less than males in control nests, whereas both sexes begged at similar rates in vitamin E-supplemented nests. Our study shows that a parasite exposure does not necessarily affect oxidative stress levels or begging intensity, but suggests that parents can compensate for negative effects of parasitism by modifying food composition. Furthermore, our results indicate that the begging capacity of the less competitive sex is constrained by antioxidant availability.

In Switzerland, the European wildcat (Felis silvestris), a native felid, is protected by national law. In recent decades, the wildcat has slowly returned to much of its original range and may have even expanded into new areas that were not known to be occupied before. For the implementation of efficient conservation actions, reliable information about the status and trend of population size and density is crucial. But so far, only one reliable estimate of density in Switzerland was produced in the northern Swiss Jura Mountains. Wildcats are relatively rare and elusive, but camera trapping has proven to be an effective method for monitoring felids. We developed and tested a monitoring protocol using camera trapping in the northern Jura Mountains (cantons of Bern and Jura) in an area of 100 km2. During 60 days, we obtained 105 pictures of phenotypical wildcats of which 98 were suitable for individual identification. We identified 13 individuals from both sides and, additionally, 5 single right‐sided flanks and 3 single left‐sided flanks that could not be matched to unique individuals. We analyzed the camera‐trap data using the R package multimark, which has been extended to include a novel spatial capture–recapture model for encounter histories that include multiple “noninvasive” marks, such as bilaterally asymmetrical left‐ and right‐sided flanks, that can be difficult (or impossible) to reliably match to individuals. Here, we present this model in detail for the first time. Based on a “semi‐complete” data likelihood, the model is less computationally demanding than Bayesian alternatives that rely on a data‐augmented complete data likelihood. The spatially explicit capture–recapture model estimated a wildcat density (95% credible interval) of 26 (17–36) per 100 km2 suitable habitat. Our integrated model produced higher abundance and density estimates with improved precision compared to single‐sided analyses, suggesting spatially explicit capture–recapture methods with multiple “noninvasive” marks can improve our ability to monitor wildcat population status.

The evolution of conspicuous begging displays has been suggested as the outcome of a conflict where offspring attempt to manipulate food allocation beyond the parental optimum. One resolution for the conflict arises via costs of begging, and oxidative stress has been proposed as a major mechanism for causing begging-induced costs. Although begging can be a physically demanding activity, the evidence for causing oxidative stress is scarce. Great tit (Parus major) parents provide food at the nest mostly from 2 different locations, which in consequence relaxes nestling competition. Here, we manipulated nestling competition by forcing parents to feed from a single location and supplemented half of the nestlings in each brood with vitamin E to test if this major antioxidant can alleviate a potential oxidative cost of begging. The design increases the cost of begging without altering parental feeding rates. Begging intensity was significantly higher when parents fed from a single location. Body mass and antioxidant capacity were not affected by the increase in begging, but oxidative damage was lower in females of the increased begging group compared with those in the control group, independent of vitamin E supplementation. The results suggest that oxidative stress is rather a minor cost of begging. Vitamin E-supplemented nestlings had a higher probability to fledge, which underlines the important role of vitamin E during development, although this might not be due to its role as an antioxidant.

Early-life stressful conditions can shape individual phenotypes and ultimately influence fitness. Oxidative stress is a pervasive threat that affects many fitness-related traits and can modulate life-history trade-offs. Yet, the extent to which exposure to oxidative stress during early life can have long-lasting effects on key fitness-related traits remains to be elucidated, particularly in natural populations of vertebrates. Using a wild population of great tits Parus major, we experimentally dosed 11-day-old birds with paraquat, a pro-oxidant molecule, aiming at increasing oxidative stress. One year later, we recaptured 39 of them as adult recruiting breeders and quantified effects of the paraquat exposure on their resistance to oxidative stress, carotenoid-based plumage coloration and male sperm performance. Despite the absence of a short-term effect of paraquat on oxidative stress measured two days later, the pre-fledging exposure to paraquat induced a reduction in individual oxidative damage measured at adulthood. Paraquat-dosed individuals also had brighter plumage, but no effect was observed on male sperm performance. For the first time in a natural population of vertebrates, we experimentally show that an early-life acute exposure to a pro-oxidant has long-lasting effects on individual resistance to oxidative stress at adulthood. Our results are in line with the environmental matching and the hormesis hypotheses but may also reflect selective disappearance of individuals with lower resistance to oxidative stress.