When there was snow on the ground, though, it would have made things very difficult for the grass-eating animals.
A small animal like a vole could make tunnels under the snow to allow it to get to the leaves and roots; but what if you were hungrier, and needed access to huge areas of grass?
Well, unless you owned a snow plough you’d have to move south.
Strangely enough, there was one sort of animal which did own a snow-plough.
In fact, a pair of them.
They were made, rather wonderfully, of ivory.