Have you stopped to think about that question? Any good rancher has at least one cow dog, but more like three or four. And usually those dogs are good enough to move the cows without any help. Well that might be over stating it, but we rarely work cows without The Rancher's Dog. Even when we are working them through the squeeze chute it is the dog's responsibility to move the cows along.
Quick side story*
When we were in college The Rancher's Dog took a spill out of the back of the truck and broke both of his back legs. We weren't sure what to do but when I looked at The Rancher I knew that we were NOT putting this dog down. We began by splinting it but that didn't keep the bones aligned well enough. The options were to either do surgery and pin it or surgery and amputate it. We opted for the pin. He seems to do well. Occaisonally we see a little limp and I'm afraid he will end up with arthritis but I don't think we really could have seen that dog go. That day was the nearest I have ever seen The Rancher cry.
But on a happier note, he is alive with all of his legs and is a master cow chaser. When we were moving cows to Badger Hole the heifers were really on the fight. I didn't get a great picture of the dogs getting the cows but some other fun ones.