I have a small mix male dog (Chico).My sister just moved into a apartment and needed me to keep her large boxer female (Baby).My dog is territorial and a big baby.He is good with the kids the cat and even other dogs.I just don't understand why my dog and my sister's dog don't get a long.Me and my sis was talking and nether of us ever seen are dogs act like this as baby is a loving dog as-well.I would like for the dogs to get a long because when winter gets here I would like to keep baby in the house so she don't freeze her tell off.Which brings me to the cat.My dog and cat well he is a kitten get a long as baby never been around cats don't want her to kill my cat.I just don't know what to do.I do have someone to help me with the proses but we just don't know what the proses it

Well you said it, your dog is territorial. They should meet again on a neutral ground, let them sniff at each other, but you need to have leashes on hand. Look for any body language that indicates them being tense. When you see this immediately step in and leash them and walk away. Try again in an hour or so.

Are both dogs altered? Some dogs just won't get along, and you can not cure the aggression, but you can watch for warning signs. You may have to keep them separated at all times. I have two dogs here right now that aren't really getting along, and they need to be watched or kenneled 24/7.

If they start showing signs of aggression, don't discipline, but quickly intervene and separate. Praise them like crazy when they are showing behavior that you think is acceptable. Remember to keep them separate when feeding, and don't show more attention to one over the other. If one dog is being the aggressor, than praise the one who is showing no aggression and take the aggressor out of the room.

I have to spread some rep. I agree with aurora!

Also.. just a little bit more to add... Your dog is probably feeling threatened.. another dog is in his space.. Another dog moved in. Things always change when the other dog "comes home".

ALWAYS greet your dog first. If your dog is wanting to be in charge, you need to honor that and vise versa.

There really isn't much you can do besides be present during this transition. Dogs will work it out on their own. Usually the first first month or two are the worse. Once both dogs figure out who is in charge, what belongs to your dog and what belongs to the other dog, things will get easy.

Remember to feed them separately, crate them separately and give them bones, chewies, treats and toys separetely for awhile.

As for the cat.. Introduce your cat now to the new dog. Let the new dog sniff some blankets that the cat sleeps on. You also might want to crate the cat and let the dog sniff the crate first with the cat not in the crate, then with the cat in the crate. Make the smell familure. It'll make it easier when you actually do introduce the cat.