The Jack Russell terrier (JRT) ais an excellent pet if you have lots of energy and love to exercise with your dog. However, a JRT left alone in an apartment all day can begin to relieve its energy in many destructive ways, including destroying furniture and becoming aggressive with other household pets. Since Jack Russells were originally bred to hunt and kill rodents, dog aggression can be common in this breed. In fact, many Jack Russell breeders recommend having no more than two JRTs in a house together unattended. These problems are more prevalent if the two dogs are close in age or of the same sex.
Exercise your Jack Russell terrier often. JRTs cannot live in an apartment with no exercise. Provide at least 90 minutes of full-blown running daily through jogging, biking or fetch games. In addition, provide mental stimulation, such as burying toys or treats in the yard or hiding your dog's food in the yard or house so he must search for it.
Determine when your JRT is snapping at your other dog and temporarily eliminate those situations. For example, if your JRT is snapping at the other dog during mealtime, feed them in separate rooms. If he snaps when both dogs are vying for your attention, separate them during this time.
Teach both dogs to go to their beds or crates on command. Teach this initially when the other dog is not present. Do this by placing a leash on your dog and tossing treats onto the spot. As he runs to the spot, say "go to your crate" or "go to bed." If he doesn't get on the bed all the way, nudge him from behind. Reward him for being on the spot. Stand over him so he can't get off the spot. If he tries to leave, block his exit with your body. Once he stops trying to leave, praise and release him with a command, such as "OK" or "go free." Practice until he can stay on his bed or in his crate for several minutes. Since Jack Russell terriers are incredibly intelligent, this shouldn't take long. Begin to practice with the other dog present once both are proficient.
Notice the signals your JRT gives before snapping. With many breeds, this can be difficult, but JRTs have very expressive faces. You should notice his pupils getting larger. You may see the whites of his eyes as well. His ears will go back, and his body will freeze. When you notice these signs, tell your dogs to go to their crates or beds. Praise correct responses. Leave them in these spots for several minutes until they calm down. This will teach your JRT what to do instead of snapping. As time goes on, you will see him choose his crate instead of undesired behaviour without your command. When he does this, reward with a favourite treat. JRTs are smart and will choose the most rewarding behaviour. Make it rewarding for him to walk away from a fight.
Keep your dogs on leash at all times when they are together. These can be thin, short leashes as long as you can grip them quickly. Keep your dogs separate when you aren't there to supervise. Your goal is to prevent the snapping while teaching your JRT what to do instead.
Many sources will advise you to support the dominant dog, which will appear to be your Jack Russell. Don't do this unless a professional behaviourist has examined your dog hierarchy thoroughly. Dog hierarchies are not strict and change with different factors. For example, one dog may be dominant when it comes to eating first, while another is dominant when it comes to toys. Any dogs that are fighting don't have a clear hierarchy. Picking which dog you think is dominant is dangerous.