How does Brian change when fighting the moose?

Up until this moment in the story, about the most fearsome creature that Brian has had to deal with is a foolbird. But a big old moose is a whole different proposition. And while Brian is washing his hands in the lake, he's suddenly attacked by one. Brian does his very best to fight back against the angry beast, but she's way too strong for him. She throws him around like a rag doll, seriously injuring his ribs and shoulder before calmly walking off to chew grass.
Stranded all alone in the wilderness, Brian has had to tame the forces of nature to survive. But the moose's sudden, senseless attack acts as a reminder that there's a limit to the control that Brian, or indeed any human being, can exert over the environment. As he falls asleep that night, Brian still can't quite understand why the moose attacked him as she did. But there's really nothing to understand; the moose's behavior is simply another example of nature red in tooth and claw, so to speak. Brian's failure to grasp this point shows us that, although he's already learned quite a lot about surviving in the wilderness, he still has a lot more to learn.