Aggressive 12 yr old Jack Rat Terrier mix
Rosco my jack rat I've had since he was about 5 months old. As he has gotten older he has become more aggressive snarling and barking at the lab we have that he has been around since he was 2 yrs old and even my daughter who was 3 yrs old when we got Rosco. With me he is not he'll do the defensive signs I tell him no firmly he stops. If he is on the couch with me he will snarl/growl at Bam our black lab mix if he gets too close or sometimes even my daughter. He seems to have mood swings one moment he is cuddling with my daughter loving her wanting attention the next I'm concerned he is going to snap. Is this old age ? He has had issues with his hip. I don't know what to do I love my dog but I can't have visitors because he won't stop barking or tries to go after their feet or ankles. Please help.