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

Understanding individual variation in fitness-related traits requires separating the environmental and genetic determinants. Telomeres are protective caps at the ends of chromosomes that are thought to be a biomarker of senescence as their length predicts mortality risk and reflect the physiological consequences of environmental conditions. The relative contribution of genetic and environmental factors to individual variation in telomere length is however unclear, yet important for understanding its evolutionary dynamics. In particular, the evidence for transgenerational effects, in terms of parental age at conception, on telomere length is mixed. Here, we investigate the heritability of telomere length, using the ‘animal model’, and parental age at conception effects on offspring telomere length in a wild population of European badgers (Meles meles). While we found no heritability of telomere length, our power to detect heritability was low and a repeatability of 2% across individual lifetimes provides a low upper limit to ordinary heritability. However, year (25%) and cohort (3%) explained greater proportions of the phenotypic variance in telomere length. There was no support for parental age at conception effects, or for longitudinal within-parental age effects on offspring telomere length. Our results indicate a lack of transgenerational effects through parental age at conception and a low potential for evolutionary change in telomere length in this population. Instead, we provide evidence that individual variation in telomere length is largely driven by environmental variation in this wild mammal.