Reproductive senescence in female S oay sheep: variation across traits and contributions of individual ageing and selective disappearance

Reproductive senescence is not universally observed across all aspects of reproductive performance in female Soay sheep, according to a study on the UNESCO World Heritage Site of St Kilda. While age-related declines were detected in fecundity and offspring traits like birth weight and early survival, no significant late-life decline was found in twinning rate. The research used longitudinal data from an unmanaged population to disentangle individual ageing effects from selective mortality, revealing that within-individual senescence and terminal declines in performance mask population-level patterns. This study highlights the complexity of reproductive ageing, challenging the assumption that all fitness traits exhibit uniform senescence.

Hayward, A. D., Wilson, A. J., Pilkington, J. G., Clutton‐Brock, T. H., Pemberton, J. M., & Kruuk, L. E. B. (2012). Reproductive senescence in female Soay sheep: variation across traits and contributions of individual ageing and selective disappearance. Functional Ecology, 27(1), 184–195. Portico. https://doi.org/10.1111/1365-2435.12029