A. D. Hayward, R. Garnier, D. Z. Childs, B. T. Grenfell, K. A. Watt, J. G. Pilkington, J. M. Pemberton & A. L. Graham. 2019. From population to individual host scale and back again: testing theories of infection and defence in the Soay sheep of St. Kilda. Chapter 4 in: Wildlife Disease Ecology: Linking Theory to Data and Application. K. Wilson, A. Fenton & D. Tompkins, Eds. Cambridge University Press: 91-128.