Here is my Leo. He's very smart but needs a lot of play time (physical and mental). He can chase and retrieve a ball for an hour straight and never tire. We also have a 90 pound black lab, Lacey, but he pushes her around like nothing to it. She eventually gives up and submits to his licking every night. I'd recommend a heeler to anybody that has the time to keep up with them.... 5 mile walk no problem. PM me for more details on where I got him.