Early Development and Population Fluctuations in Soay Sheep

Abstract

In the Soay sheep population of Hirta (St. Kilda), high winter mortality occurs every 3-4 years following summers when population density exceeds 2.2 sheep ha −1 . During these die-offs, more than 50% of adults, 70% of yearlings and 90% of lambs die and population density falls by around 65%. This paper investigates the extent to which density-related changes in early growth might be responsible for fluctuations in over-winter survival and population size