I have done dog rescue for 8 years. when a Jack Russel is board or unhappy (Lack of hard and I mean hard exercise they tend to get aggressive and try to become pack leader.

Dose your dog know YOU are the pack leader?
Is the dog getting lots of exercise?
Jacks are one of the smartest dogs if it keeps going try a muzzle only when he or she is biting your other dogs it will learn not to do that.

good luck

Member 1146644 answered on 12/26/12. Helpful? / 0