Hmmm im not sure if its to early to worry yet but my wife has a 2 year old rat terrier named chico hes always been the only dog and today i went to the pound and bought a mutt puppy they say its a lab mix but i think its got some german sheppard in him and chico who is also a boy is crazy around him and doesnt like him for someone its wierd because they will be fine for a minute and sniffin each other and everything then out of nowhere chico tries to attacc him... any help would be greatly appreciated... im hopin that in a few days he will juss get used to him and be ok..