As Sam tells us in his diary entry for November 26, hunters are excellent friends if they can be used correctly. In other words, the activities of hunters can inadvertently help Sam in his efforts to survive out in the wilderness.
Sam doesn't want the hunters to see him, but he follows them all the same, as he's acutely aware of all the benefits that they will bring. To avoid being seen by them, he follows them using the tops of trees. As hunters don't look up, this is a good way of avoiding detection.
An added advantage of moving through the trees like this is that Sam can see not only what the hunters shoot, but where their quarry falls. If you're very careful, then you can grab hold of the dead animal and hide it before the hunters get a chance to reach it. This is how Sam got his third deer.
Later on, Bando shows Sam an article from a New York newspaper entitled
WILD BOY SUSPECTED LIVING OFF DEER AND NUTS IN WILDERNESS OF CATSKILLS.
The article states, according to several hunters, that the boy in question—who is, of course, Sam—stole deer from them during the hunting season. Sam is most indignant on hearing this. He claims that he only took the wounded deer that the hunters shot but couldn't find.
In any case, it's unlikely that Sam would have had so much deer meat to eat had he not decided to follow the hunters and grabbed the deer they'd killed before they had a chance to get to them.