Beginning in the mid 1800s the Australian Koolie breed evolved on farms without structured breeding plans and standards, into an elite working dog with a broad range of skills and abilities. They are physically and mentally able to work all day beside their human workmate, mustering sheep, driving cattle, loading trucks, whatever is necessary - they thrilled to be able to help in any way possible. At the end of the day Koolies are happy to curl up at their owner's feet in camp, keeping him company and an eye out for trouble. Because of the long history of good working dogs being bred to good working dogs and also because Koolies have a diverse gene pool, they have few physical problems, are easy breeding and sound. Also due to the concentration on breeding for working ability they have evolved in a range of sizes, coat colors, coat length and ear set, which has helped them adapt to the diverse range of jobs they take on. Ears are usually pricked but can be semi pricked or dropped. They are a medium-size working breed that has both the occasional bigger dog and some small, lighter dogs all suited to the different tasks they take on.