They cannot lock their jaws, that myth has been busted since it began... They are just bred to hold onto the bull until the owner was safe, and the dog was mauled.Wow, this comment really blew me away. How much actual research went behind this answer? Pit bulls were NOT, I repeat NOT bred for fighting. If you would read up a little they were bred to protect their owners from being overtaken by, wait for it.............
BULLS, as in MALE COWS. Hence the bull in their name. The reason they were bred with jaws that lock is so that if their owner was working with bulls or cows, and say one of the bulls decided to harass the human, the dog could latch onto the bull and lock his jaws so that the human could get to safety while the bull was distracted by the dog.
That is the reason why they are fearless in situations where any other animal would run for safety. Because they are WORKING dogs and are there to PROTECT their owners from harm that may be caused by a 2000+ pound animal.
Please......lets all do a little research before we pass out our opinions as fact.
But yes, they were not used in dogfighting until bull baiting was illegal. They were also used as ratters in shows where they'd put a load of rats into a pit and let to dog go.
Now, about the situation at hand, your pup sounds like he's being overwhelmed, and is testing new people and dogs.
I would highly suggest taking him to a good obedience class, and make sure it is one that uses positive reinforcement. This breed does not do well with the "I'm the boss, do what I say or I'll collar-hang you" tough guy thing a lot of trainers seem to do to this breed.
A good thing to do when meeting strangers is to have him sit and stay while they approach, if he growls ONCE, immediately go the other way, once he's calm, repeat, if he finally allows someone to get close enough to touch him, have them drop a small piece of chicken, ALL dogs love chicken. He will begin to see that aggression is not accepted, and strangers mean a tasty treat.
It may be good to set this up with a friend or family member, or it would likely not work, since I doubt a real stranger would put up with all of this.
Do this with as many different people as you can.
Dog aggression... In this breed, it can be hard to break them of. Some of them simply do not like dogs, especially small ones, as terriers have a high prey-drive.
This can be managed, but I don't know if you can have him being dog-friendly unless you get him in a class. I've managed my adult pitties problems using the same technique as with people, have an owner with a very controlled and non-responsive (meaning if your pup is grumbling and fussing he won't lunge and act nasty back) dog do pretty much the same as with the person training. He acts up at all, and he is taken away.
These are two very, very important things. There will always be a time when you are approached by a strange unleashed dog on your walks, and it could be the death to either dog if yours is out of control.
But thankfully, you are trying to nip this in the bud, and it sounds manageable.
Pups this age will strut their stuff. They really aren't as big as they think.
Check out www.seefido.com and on there, NILIF (nothing in life is free).