It's not always easy to tell the difference between rat terriers and toy fox terriers. That's because they're closely related, with the toy fox being one of the breeds used in the creation of the rat. The American Kennel Club considers the toy fox terrier a member of the toy group and places the rat terrier in the terrier category.
Rat terriers come in two separate sizes: miniature and standard. The miniature rat terrier matures between 10 and 13 inches tall at the shoulder, while the standard rat terrier ranges in height from 13 to 18 inches. The toy fox terrier stands between 8.5 to 11.5 inches tall when full-grown -- so acceptable toy fox terrier sizes are slightly less and within the range of those of miniature rat terriers, but they're much smaller than standard rat terriers.
Both breeds sport short, easy-care coats. Acceptable coat colors for the rat terrier consist of some combination of pied, or white with large patches of other shades. The AKC standard doesn't permit solid-colored rat terriers or toy fox terriers, or those of two shades if one of them isn't white. While black-and-white pied is the dominant color in the breed, other colors with white include tan, red, lemon, blue and chocolate. The toy fox terrier usually has a predominately white body with a black, tan, chocolate-and-tan or black-and-tan head. Small patches of body spots the same color or colors as the head are acceptable.
The toy fox terrier, basically a smaller version of the fox terrier, has the more typical terrier temperament. He is more territorial and therefore more likely to take on other dogs if he feels threatened, no matter their size. The rat terrier -- a relatively recent breed with beagle, Chihuahua and whippet in his lineage along with terrier lines -- tends to be less hyper than the typical terrier. Both breeds are smart and active. Their terrier side is on display with their love of digging, barking and chasing after small prey. If you have small children, the rat terrier might be the better choice.
Exercise and Training
Both breeds have moderate exercise needs but a low boredom threshold. That means you must keep them occupied or you aren't going to like the way they decide to entertain themselves. Crate-train your rat terrier or toy fox terrier early on. When you're home, give the dog lots of play, training and exercise time, taking him for walks and throwing balls. Rat terriers are prone to separation anxiety, with destructive results, so take that possibility into consideration if the dog will be home alone for much of the day. Another, well-behaved dog in the house can ease his fears. You can also purchase toys designed to be filled with food -- he must work at obtaining the treats. Both breeds do well in canine sports, including agility and Flyball.