The Changes;
Over a ten million year period, the ice sheets of Arda have covered vast amounts of the Northern continents during the Ice Age. This allowed Arctic Foxes to gradually migrate south with the growing Tundra, though many foxes stayed behind to face the changing climate. Tectonic plate movement marked the end of the Ice Age on Arda in that this caused a great amount of volcanic activity, thus greatly raising the surface temperature on Planet Arda. As the ice sheets shrank back to the North, many of the Foxes migrated with the ice, but some populations of the Foxes stayed behind and evolved to the gradually warming climate of what would become the desert and grasslands of Valimore. After this ten million year period came to an end, the volcanic activities return to normal, as well as the surface temperature. The Arctic Foxes that stayed behind to face the Ice and Snow region of Valimore moved south as the ice sheets melted. Thus leaving no Tundra remaining, only the Taiga regions and small amounts of Snow and Ice biomes of furthest North regions of Valimore. However, during this, a great majority of the Arctic Fox population that did not migrate with the Foxes that migrated with the growing tundra, stayed behind in the Tundra. The Tundra, over this long period of time, became a cold, harsh, icy region. The Foxes that did move south with the expanding Tundra flourished due to the more abundant plant and animal life, but over this time, they adapted to this environment, and once the ice melted and they migrated back north to follow the tundra, they died off, due to a lesser struggle for survival in the further south biome, all of a sudden, put into a nearly barren region. The Foxes that did stay behind to face this new and changing biome developed many new and much more efficient skills and adaptations. With the decreasing temperatures and harsher climate, all of the surface plant life died off, and all but one other species of mammal moved south. The species that remained was the Arctic Lemming.