There is no breed known as the Norwegian Mastiff. Mastiff varieties include the Tibetan and English Mastiffs. Mastiffs are protective, territorial dogs that need heavy training and socialization to trust strangers.
Mastiffs are very large, averaging around 150 to 200 pounds, and need to be walked twice daily due to their laziness within the house. Tibetan Mastiffs are slightly smaller than the average Mastiff and have more fur, whereas English Mastiffs are large, with a short coat. All Mastiffs are loud snorers and drool heavily, but they do not bark as much as other breeds. Though they enjoy being inside, they still need to live in a large home with a large yard in which to exercise
Mastiffs originated from one of the earliest breeds of dogs, the Molosser. This dog was a very large breed that lived more than 2,500 years ago. It acted as a guard against predators in the mountains of Asia, Tibet and Northern India. The first breeds of Mastiffs were used as entertainment in southern Europe, fighting against lions for people's amusement. Due to this upbringing, Mastiffs have a tendency to become aggressive if not given regular exercise and love, though they are very kind and gentle otherwise. Once in England, Mastiffs became popular as patrol dogs for large estates, returning to the instincts of their ancestors and protecting against predators.