Sil H. J. van Lieshout, Amanda Bretman, Chris Newman, Christina D. Buesching, David W. Macdonald, Hannah L Dugdale 

Telomeres, protective caps at the end of chromosomes, maintain genomic stability and function as a biomarker of senescence in many vertebrate species. Telomere length at different ages has been related to (subsequent) lifespan, but to date only one laboratory-based study has shown a direct link between early-life telomere length and lifespan. Whether this relationship holds in wild populations, where individuals are subject to variable natural conditions that may mask relationships seen in controlled laboratory settings, remains unknown. Here, we provide evidence that early-life telomere length predicts survival to adulthood in a wild population of European badgers (Meles meles). Furthermore, both early-life telomere length and telomere rate of change predict lifespan. We found a complex cross-sectional relationship between telomere length and age, where telomeres shortened over the first 38 months, but with no uniform loss after this point. We found little within-individual consistency in telomere length across lifespan, where telomere length did not predict residual lifespan. Importantly, we also observed increases in mean telomere length within individuals, which could not be explained by measurement error alone. Early-life telomere length varied distinctly among cohorts, indicating a role for early-life environment and additive genetic effects. Our results elaborate on the dynamic way that telomeres function as a biomarker of senescence in a wild mammal, where telomere length and rate of change can reflect short-term and lasting effects of early-life conditions on individual life-history.