The Great Pyrenees, known as the Pyrenean Mountain Dog outside of North America, is a large breed of dog used as a livestock guardian dog. It should not be confused with the Pyrenean Mastiff.
As late as 1874 the breed was not completely standardized in appearance, with two major subtypes recorded, the Western and the Eastern. They are related to several other large, white, European livestock guardian dogs (LGD), including the Maremma Sheepdog (Italy), the Kuvasz (Hungary), the Akbash (Turkey) and the Polish Tatra Sheepdog or Polski Owczarek Podhalański, and somewhat less closely to the Newfoundland and the St. Bernard. According to the Great Pyrenees Club of America, the Great Pyrenees is naturally nocturnal and aggressive with any predators that may harm its flock. However, the breed can typically be trusted with small, young and helpless animals of any kind due to its natural guardian instinct.The Great Pyrenees breed has experienced a dramatic falloff in the number of U.S. AKC breed registrations from 2000 to 2010. The breed was ranked at #45 in 2000 but by 2010 had dropped to #71. In 2013 the breed was ranked #69. Other large breeds in the same working group classification, the Newfoundland and the St. Bernard, have fared far better in maintaining their breed rankings, being ranked #44 and #45, respectively, in 2010.