The Tibetan Mastiff is the most fierce guard dog of the high plateau. Tibetan nomads have kept these dogs as part of the family since time immemorial. Marco Polo mentioned them in his travels and was believed to have brought two of these dogs home with him. These hardy beasts can live without shelter even at elevations of 4500 meters or higher. However the current situation of the Tibetan Mastiff became grim as more and more lowland dogs were brought into the Tibetan plateau and began to mate with the purebreds, resulting in mix-breeds that diluted the pedigree and blood line of this ancient line.