Answer:
Buck takes the place of the lead dog by displaying his dominance, intelligence, and leadership qualities.
Since spitz has been killed the pack requires new lead dog but sol-leks was chosen as the new lead dog . but buck didnt want that to happen it and he springs upon sol-leks in fury , indicating his desire to be the leader of the pack .
buck attacks sol-leks again and again and eventually shows himself superior and capable of being the lead dog of the pack .