the biggest thing I know is that many times Border Collies,and Kelpies, dont get along with dogs that have high set tails and very upright postures, its because the dog perminantly looks threatning, while BCs/Kelpies are "eye" dogs they slink around and wlays look like they are on the prowl, the potures and looks are often mistook by the other dogs to be threatning, and therefore they either run or fight.