The Fila Brasileiro (Portuguese pronunciation: [ˈfilɐ ˌbraziˈlejɾu]) also known as the Brazilian Mastiff is a large working breed of dog developed in Brazil. It is known for its superb tracking ability, aggressiveness and an unforgiving impetuous temperament. When a Brazilian Mastiff finds its quarry, it does not attack it, but rather holds it at bay until the hunter arrives. Owing to these qualities, the Brazilian Mastiff is used as a guard dog, as a shepherd dog for herding livestock and as a hunting dog for tracking and controlling large prey. When slavery was legal in Brazil, the Brazilian Mastiff was used to return fugitives unharmed to their slave masters. This breed has been banned in many countries because of its temperament and potential for aggression.The Brazilian Mastiffs are known to be naturally protective. It is also known for its extreme wariness of strangers and agility when protecting or defending its master. The dedication and obedience of the Fila Brasileiro has found its way into Brazilian saying “As faithful as a Fila”[15]

The Fila Brasileiro temperament is what characterizes the dog. The Portuguese word for their temperament is Ojeriza, which directly translated into English means dislike and distrust. The socialization period (about the first year with the first 6–8 months being the most important) of the dog’s life is crucial to the temperament of the individual dog. If the pup is exposed to a lot of people in a positive manner (known as ‘socializing’), the pup (keeping in mind the dog’s natural protective instincts) can be encouraged to behave in a calm manner in public, but emphasis should be placed on the fact that socialization is done differently from other breeds. Despite extensive socialization, the fila is instinctively protective and will naturally guard and protect its owner, their family members and the family pets; this is not something that needs to be trained, it is an innate trait. Strangers should not be left unattended with a Fila and, like all other guardian breeds, it may not be the best choice for those who have frequent visitors to their homes. Lack of all socialization with strangers at a young age will result in a dog which is very anti-social.