Many of today's Spanish breeds of mastiffs claim to be this breed; the Spanish Mastiff, the Pyrenean Mastiff, and the old Alano Español. Some Ca de Bestiar breeders believe that their dog was the breed that King James I brought over. Some Ca de Bestiar breeders believe that their dog was the breed that King James I brought over. The Ca de Bestiar was well regarded by the locals as a good herder and guardian. Their sizes and shapes would depend on the function people were looking for. Whatever the function, they could withstand high temperatures. The size, shape and temperament varies greatly between lines.