New Jack Russell - addition to family

Question
I have a 8 yr old lab mix and a 13 yr old Shepherd Mix.  Recently added a 3 year old Jack Russell mix rescue.  He leaves my shepherd alone (who is dominant) but humps my lab mix (all are fixed).  I've begun spraying him with water when he does this, and I know it is a dominance behavior, but is there anything else I can do to stop it?  Could it lead to aggressive behavior like fighting?

Answer
You're not accomplishing a thing by spraying this dog, except perhaps eroding any trust he might be building in you.  You need some control over this "pack".  Your JRT mix is, by nature and AGE, the most likely candidate for leader...but it's YOU who should fill that role.

Use positive reinforcement training to teach your JRT a basic obedience behavior.  "Sit" is the easiest, but use another word (most people destroy the value of "commands" by training incorrectly, overusing the word, etc., so using a brand new word is the best choice.)  This training, which will take approximately three weeks (in order to obtain a 100% solid response), should be done with the JRT mix separately from the other dogs.  Once he is responding EVERY TIME, use your "sit" command to make this dog EARN EVERYTHING.  This means: his food, going out, coming in, playing, interacting with you, treats, going in/out of doorways with you.  Keep him on a house tab (lightweight nylon leash) for the next 6 to 8 weeks and use the house tab to control him if he charges through doorways ahead of you, up or down stairs, etc., and especially during his interaction with the Lab.  Before he is conditioned to his new "sit" command, the house tab will allow you to remove him from the Lab (without saying a WORD or TOUCHING HIM).  If you need information about positive reinforcement training, go to Karen Pryor's web site or purchase Paul Owens' "The Dog Whisperer" (NOT Cesar Milan!! )

Once you have obtained a 100% (EVERY TIME) conditioned response to your command for "sit" and have used it to make the dog earn everything for about two weeks, you should have effectively created a bond of trust with your JRT and elevated yourself to pack leader in his mind.  NOW, if he persists in humping the Lab (which he might self extinguish by this time), remove him with the house tab while growling a "Nuh!" in a guttural voice.  Bring him to your side, make him sit (for reward), then release the tab.  Repeat this several more times and your JRT should begin to defer to YOUR dominance and stop the behavior.