Why are pine marten populations expanding in Scotland and Ireland yet apparently not doing the same in England and Wales?
The short answer is that we don’t know, although several reasons have been suggested. It may be that the habitat is more suitable in Scotland and Ireland as there is more forestry cover than in England and Wales. It has been suggested that the fox population in England and Wales is higher than that in Ireland in particular, leaving pine martens more susceptible to predation. Furthermore, there are fewer carnivores in Ireland (notably the absence of the weasel), therefore the pine marten may face less competition for prey.