These people subscribe to magazines and newsletters and buy books for animal lovers. They read about how to be responsible pet owners, as well as vital information about animal health, behavior, grooming, nutrition, training, breeding, legislation, veterinary topics, pet-related human interest stories, etc. Most of them are members of clubs that group people of similar pet interests together. Source: pet owners association that mail newsletters to their members; pet shops that sell books and other literature (along with supplies for pets), to their clients.