Sil H. J. van Lieshout, Elisa Perez Badás, Julius G. Bright Ross, Amanda Bretman, Chris Newman, Christina D. Buesching, Terry Burke, David W. Macdonald, Hannah L Dugdale 

Early-life environmental conditions can provide a source of individual variation in life-history strategies and senescence patterns. Conditions experienced in early life can be quantified by measuring telomere length, which can act as a biomarker of survival probability. Here, we investigate whether seasonal changes, weather conditions, and group size are associated with early-life and/or early-adulthood telomere length in a wild population of European badgers (Meles meles). We found substantial intra-annual changes in telomere length during the first three years of life (both between and within individuals), with shorter telomere lengths from spring to winter and longer telomere lengths over the winter torpor period. In terms of weather conditions, linked to food availability and foraging success, cubs born in warmer, wetter springs with low rainfall variability had longer early-life (<1 year old) telomere lengths. Additionally, cubs born in groups with more cubs did not have significantly shorter early-life telomeres, providing no evidence of resource constraint from cub competition. We also found that our previously documented positive association between early-life telomere length and cub survival probability remained when social and weather variables were included. Finally, after sexual maturity, in early adulthood (i.e. 12–36 months) we found no significant association between same-sex adult group size and telomere length (i.e. no effect of intra-sexual competition). Overall we show that controlling for seasonal effects is important in telomere length analyses, and that badger telomere length functions as a biomarker that reflects the physiological consequences of early-life adversity and subsequent effects on cub survival probability.