Old dog acting out and showing aggression towards new dog. What do I do?!

I have a male Basenji-Shiba Inu mix that seems to be harboring some aggression towards our recently adopted male Lab and he has also started acting out (doesn't obey commands, steals things). He's gotten along with our female Lab mix for the last two years and has gotten along wonderfully with other dogs of both sexes at the dog park during the two years we've had them. But, with the adoption of our second Lab last weekend, he's been less than welcoming. He hasn't been attacking the new lab, but he growls and bares his teeth when he gets to close. I think it's probably more of a jealousy issue, as our girl was doing the same thing the first few days. However, although our girl now gets along fine with the new lab, our boy continues to display jealousy and agression towards our new guy. Are there any suggestions or techniques I could try to quell the situation? We've tried rewarding our Basenji-Shiba mix with praise, pets, and treats for exhibiting calm behaviour around the Lab.

Asked by Member 1041399 on Jul 18th 2011 Tagged aggression, samesex, actingout in Behavior & Training