Jack Russell Terrier puppies The Jack Russell Terrier can be aggressive with other dogs and should be socialized when young if possible. It is however, still a hunting dog, so don't expect it to cuddle up with your gerbil or guinea pig. It's natural hunting instinct will kick in and could result in the chasing of the family cat. It may try to be dominant over other dogs, regardless of size. Jack Russell Terriers are fearless. Visitors will always be announced with a distinctive bark. Pls call or text via: (xxx) xxx-xxx6