Can a Brazilian Mastiff puppy live safely with small Rat Terriers?
Anytime there is a great size difference between dogs in the same household, there is significant risk that the smaller dogs may be injured at some point - either during play, or in an actual fight if this were ever to occur. This doesn't necessarily mean that you can't have both large and small breeds in the same home (many people do!), but it does mean that you should be aware that this is somewhat risky for your smaller dogs, even if the new pup is raised around them.
You should also be aware that genetics play a huge role in aggression towards other dogs - so if you do opt to get a Fila, I would make very certain that the puppy comes from a line of well-bred dogs with no history of dog aggression. This doesn't guarantee that you won't have any problems, but it will reduce the risk.
If you prefer a less risky option, you could opt for another small breed that is a similar size to your rat terriers - this way, even if issues do crop up between the dogs as they get older, the odds of serious injuries or death is much less.
Updated on September 23rd, 2025