"Sheep Dog" describes a type, not one breed. It usually points to a herding dog or a mix from the family that includes Border Collies, Old English Sheepdogs, Shetland Sheepdogs, Australian Shepherds and Collies. Those breeds were developed mostly in Britain and Europe over the last few centuries to gather and steer flocks, and the instinct to watch, circle and control movement is inherited.
In a city like Mesa, that instinct often shows up as intense focus on joggers, bikes, kids and cars. Many of these dogs are sensitive, quick learners that bond closely with their people and are happiest with a daily job, such as training games, agility or scent work. Coats range from sleek to heavily double-coated, and dogs of any mix vary in energy and temperament.