Add Yahoo as a preferred source to see more of our stories on Google. A close-up of a frost-covered reindeer and a white ptarmigan feeding together on green moss in a hole dug into the deep snow.© A-Z ...

Reindeer are considered a keystone species. During the winter, herds of reindeer attract smaller animals like ptarmigans due to the holes created by foraging patterns. Ptarmigans eat whatever is left ...