Impact of Climate, Habitat and Scale on the Population Dynamics of Feral Goats on the Isle of Rum, NW Scotland

Abstract

Although feral goats are an invasive species renowned for their ability to survive in degraded habitats, their capacity to occupy high latitude habitats is severely restricted. I analyse long term data on the lifehistory and demography of a feral goat population on the Isle of Rum, NW Scotland, in relation to both longterm variation in climatic variables and within-population variation in environmental variables. While exhibiting many features characteristic of ungulate lifehistory, goats are especially sensitive to variations in thermal conditions, especially during winter. This is compounded by the fact that, at the latitude of Rum, goats give birth in mid-winter, even though this imposes significant stress on both mother and kid. Longterm patterns in population growth rates are correlated with winter temperature and the NAO index, with little evidence for density-dependent effects (except in respect of fertility). In addition, there was evidence that the presence of a large sympatric red deer population was limiting the goats capacity to increase by denying them access to preferred foraging habitat. Nonetheless, their unusual sensitivity to the thermal environment implies that the goat population will increase significantly with progressive climate warming.