Jack Russells Have Pack Dog Mentality
When bringing animals together it's important not to leave them unattended for any length of time, especially if there are more than two Jacks. Jacks have a pack hunting mentality, a natural instinct from hundreds of years of breeding. They will exhibit those traits. It's very unwise to leave two or more jacks alone with a cat or another pet. A Jack that has previously been non-aggressive towards cats and other animals may take part in the killing of such an animal when in the pack environment. There have even been cases where some Jacks have ganged up on a weaker one in the pack and injured or even killed it. A close eye on the dynamic of any pet gathering involving the Jack Russell is advisable. Again, it is possible that this can happen no matter how cute or well trained your dog is. It's in their nature, the behavior is instinctual and no amount of training will overpower the animal's instincts entirely.
First time owners will often find they are overwhelmed and wonder why the dog's needs are so demanding. It's best to know what you are getting into before hand and make sure that your home has the time and environment to meet those needs before bringing a Jack Russell home. Although the Jack Russell owner always has to be alert of the potential dangers, many owners will eventually come to think of their Jack as more of a person than a dog. The unique and intelligent personalities exhibited find many owners considering their Jacks to be like a child. Owners will even find themselves worried about their Jack's mood and happiness. This is because the Jack is prone to mood swings.