Who is David Smallhorn from Brian's Winter and what is their importance?

David Smallhorn is a Cree trapper who spends his winters in the woods several miles from the lake where Brian's plane crashes. David becomes aware of Brian almost from the moment he and his family arrive in the woods, but they give him space because many bush people prefer to be left alone. When Brian hears David firing his gun in the woods, he thinks it might be trees exploding from the cold, but then realizes it is too warm for the trees to explode from frozen sap. Brian goes in search of the sound and stumbles onto David's small home. It is through this meeting with David that Brian is rescued.