Early-life effects on telomere dynamics in European badgers (Meles meles)

Despite extensive evidence of senescence, the decline in performance with age, in wild populations, the drivers of individual variation in senescence patterns are still unresolved. In this thesis, I study how early-life environmental, genetic and transgenerational effects contribute to individual variation in senescence patterns, using telomere dynamics, in a wild population of European badgers (Meles meles). I discovered that telomere length forms a complex relationship with age, with both decreases and increases in telomere length that cannot be fully explained by measurement error. Telomere length was not sex-specific, but early-life telomere length predicts survival to adulthood (>1 year old) and lifespan. Within-individual changes in telomere length could be due to age-related changes in leukocyte cell composition in response to social conditions. While variation in (early-life) telomere length was associated with the abundance and variation in food availability, and natal but not adult social conditions, I found no evidence for heritability of telomere length or transgenerational effects, through parental age at conception effects. Additionally, individuals experiencing matching early- and later-life conditions had longer lifespans, even though there was only moderate autocorrelation in environmental quality, but this also depended on the mean environmental quality across adulthood. I also developed a novel approach to the analysis of long-term studies, termed slicing, which overcomes problems with confounding effects and cross-classified data structures. My research shows that individual variation in telomere length and senescence is a consequence of early-life environmental, not genetic or transgenerational, effects in European badgers. In addition, I show the potential for adaptive responses in anticipation of the adult environment and the importance of studying both the mean of and variability in early-life conditions to fully understand the selective pressures on senescence.