From population to individual host scale and back again: testing theories of infection and defence in the Soay sheep of St Kilda

A long-term ecological and genetic study of the unmanaged Soay sheep population on St Kilda reveals critical insights into the interplay between host-parasite dynamics, immune defense, and population regulation. The research demonstrates that parasite burden significantly influences individual sheep survival and fecundity, while also shaping population dynamics through density-dependent effects. By integrating over 30 years of data on sheep demographics, genetics, and parasite diversity, the study identifies how natural selection has molded immune function in response to varying transmission intensity. This comprehensive approach bridges population-scale observations with fine-grained individual-level analyses, providing empirical validation for theoretical models in disease ecology.

Hayward, A. D., Garnier, R., Childs, D. Z., Grenfell, B. T., Watt, K. A., Pilkington, J. G., Pemberton, J. M., & Graham, A. L. (2019). From population to individual host scale and back again: testing theories of infection and defence in the Soay sheep of St Kilda. Wildlife Disease Ecology, 91–128. https://doi.org/10.1017/9781316479964.004