Reindeer

Reindeer are one of the rarer, and yet more famous of all species in Europe. The legendary mounts of St. Nicholas' sleigh may well just be a legend. Yet their species is real and plain to see, for those who can find them. Roaming the apparent wastes of Northernmost Europe, these mighty beasts have found a new lease of life in domestic use. After the Russian civil war the nation was lacking most things one could imagine. Included in this was horses. Needed in agriculture, the army, and as a means of transport in the vast rural areas between cities that modern industry had yet to reach. 
In desperation, the people of the Kola turned to newly independent Finland and purchased reindeer from several of the vast herds that roam the region in the hopes of making use of them as they had once horses. This desperate experiment was surprisingly successful, the hardy animals proving as well suited to the bitter colds of the Russian winter as any large beast can be. In the years since then their use has spread across Russia from Karelia to Kamchatka. 
Able to pull heavy loads long distances over roads which are described as "difficult" when one is being generous, "improvised" when feeling euphemistic, and "non-existent" when honest these hardy beast were hardly obvious beasts of burden. Especially when compared to their skittish cousins of the deer species more common to the rest of Europe. Yet it seems the legend of St. Nichola's sleigh may have some truth too it after all. No doubt a source of great joy for children all over the world who eagerly await his visits, whatever night of the year they might occur on. Though wat a 4^th century Greek Bishop living in Anatolia would need reindeer, much less a sleigh for, is anyone's guess.