Companion dogs naturally defend their owners against hostile aggression because they are protecting one of their own and the alpha dog of the pack who is their owner. Most dogs have a very strong instinct to protect those that they consider companions, team members or members of the pack. Although one website says that dogs won’t protect anyone from another person.
I disagree. Some time ago I wrote about a gang of armed burglars who after they entered the home the owner’s dog attacked them and chased them away. I can’t see why you would argue that dogs won’t protect their owner from another person because dogs treat people as another potentially hostile animal.
Dog society and human society match up very well because they’re very similar. And a puppy that is socialised to humans is powerfully attached to both dogs and people i.e. both species of animal. Humans act the role of dog companions very easily. In other words dogs integrate very nicely into the human “pack” which is the family. Humans are a member of the dog’s pack which, as mentioned, is why they protect humans including their owner who are part of their perceived pack.
I’m told that the most protective dogs on a breed-by-breed basis are German shepherds, Rottweilers, Doberman Pinschers, Bullmastiffs, Giant Schnauzers, Rhodesian Ridgebacks and Belgian Malinois. Petguide.com says that the dog with the strongest bite is the Cane Corso at 700 psi. German Shephards have a bite at 238 psi. Purina.co.uk say that dogs are so loyal to people because they give them food and shelter. It’s an act of gratefulness.