The most noticeable physical difference is the ears. Where Jack Russells ears flop over and bend down towards the front, Rat Terrier ears often point straight up (although in the mix both ear types are common). There is also a lot more variety in coat colors and patterns in Rat Terriers. Shedding and grooming requirements are fairly similar between both breeds, so Jack Rat Terriers aren't high-maintenance as far a grooming goes. Jack Russell Rat Terriers can also grow a little bigger than purebred Jack Russells. The average Rat Terrier grows to between 13 and 18 inches (33 to 46 cm), while standard height for a Jack Russell Terrier is between 10 and 15 inches (25- 38cm).
The Rat Terrier is really a pretty mixed up breed in itself, made up of bits of Beagle and various other terriers and hounds. There is also a miniature version of the Rat Terrier, so make sure you know what you're getting when you buy a puppy. It's always good practice to ask to see the parents.
Want to know what to expect from the personality of a Jack Russell Rat Terrier cross? Here are some of the common traits from the Jack Russell side:
sense of humor
impressive physical strength
strong hunting instinct
Expect to see some of these, combined with Rat Terrier traits such as:
more awareness of moods and body language
lower intensity - more relaxation oriented than JRTs
What Are The Benefits and Downsides of a Jack Russell Rat Terrier?
Jack Russell Rat Terriers are brilliant hunters and excellent as pest control dogs. If you live on a farm or in the country, this could make an excellent working dog.
This is not to say these mixes are only good for working dogs - they can make good pets too. You will need to have an active lifestyle because these dogs need as much exercise as purebred Jack Russells, although they can also be more of a snuggle dog. Be prepared to handle a strong hunting instinct and a dog that may tend to follow its nose somewhat. As with a purebred, a Jack Russell Rat Terrier mix breed will need plenty of socialization as a puppy and some good firm training in basic commands. You may find a Rat Terrier/Jack Russell cross to be a little easier to train than a purebred Jack Russell because of the emotional intelligence that comes from the Rat Terrier side.
Jack Rat Training
If you want to learn more about training and controlling your Jack Rat, my ebook is bound to save you hours of training trial and error and relieve a lot of stress from the process: The Jack Russell Lover's Ultimate Guide to Training comes complete with a full chapter on mix breeds.