What are the characteristics that Buck have in chapter 3 of the call of the wild

Buck's beastly nature steadily grows, though he makes not sign to betray it to the others. He picks no fights, concentrating solely on getting through each day as best he can. Sensing a rival, Spitz never misses an opportunity to remind Buck of his place. Many times he attempts to start a fight that must end in one of their deaths. Buck resists his growing dislike of Spitz until one particularly difficult and cold night, Spitz takes over Buck's nest while he has gone to eat his ration. Furious, Buck leaps at Spitz.