The Australian Cattle Dog aka Blue heeler or Queensland heeler breed started in the 1800s. ACD is a smaller but intense working breed, a lot of dog in a smaller body. They tend to be solitary working dogs, can be prey driven and as with many solitary working breeds, some may not care for other dogs. Show lines may be less high strung but still need their typical exercise needs met. 17 - 20", 33 - 50 lbs. #ACD #Australian #cattle #dog #small #medium #purebred