The Scotch half breed treats the sled dogs fairly even though he pushes them extremely hard. He comes into Buck's life after Francois and Perrault depart the story. The author may have purposely unnamed this character to add to the idea that Buck's time with him was characterized as "business-like." Buck did the work. That's all there was for him to do. No time to become emotionally involved with his owner. In a sense, this experience served Buck well in that it taught him to work hard. And in doing so, the "reward" would be satisfaction that the work was done. That's all. Task + hard work = task finished. As a consequence, it left Buck longing for more out of his life. Could a demanding master also be a loving master? That question would be answered when John Thornton subsequently became Buck's master.
The Scotch half-breed was kind towards the dogs. He checked up on them whenever they made it to camp and ensured their feet were fine. At one point he removed Dave from his traces because he was hurt. He hoped the dog would run free behind the pack. The Scotch treated his dogs well, but the work and terrain made them suffer.
“Mush on, poor sore feets,” the driver encouraged them as they tottered down the main street of Skaguay.
“Dis is de las’. Den we get one long res’. Eh? For sure. One bully long res’.”
The drivers confidently expected a long stopover.
The dogs lost weight and became irritable because the work was hard, and they did not get enough time to sleep. They were expected to deliver mail on a very frequent basis which snuffed out their strength. Buck somehow understood that the dogs were only valued for their work, and they reciprocated with a heightened sense of duty. This understanding was important to Buck’s future because it saved his life.
Buck heard the chaffering, saw the money pass between the man and the Government agent, and knew that the Scotch half-breed and the mail-train drivers were passing out of his life on the heels of Perrault and François and the others who had gone before.
Buck and the other dogs were sold to new owners who knew nothing about traveling with the dogs. They made many mistakes that led to the death of a number of new dogs and Buck’s old comrades. Sensing the impending death and danger, Buck objected to his duty in spite of his new master’s furious attacks. It was then that he was saved by Thornton from the brutality expressed by his new master. The new owners together with Buck’s old comrades rode to their deaths soon afterwards. Lessons learned by Buck probably saved the dog's life.
This was the first time Buck had failed, in itself a sufficient reason to drive Hal into a rage. He exchanged the whip for the customary club. Buck refused to move under the rain of heavier blows which now fell upon him. Like his mates, he was barely able to get up, but, unlike them, he had made up his mind not to get up.
They saw Charles turn and make one step to run back, and then a whole section of ice give way and dogs and humans disappear.