The wolves need the bison to break rank, but the tables are turning and now the wolves have to retreat. The pack focus their attention on the rear of the herd and the bison/ begin to panic. 

 

A young bison falls behind. Even this yelling dwarfs the wolves. Running head down, the herd's only thought is to escape, a stroke of luck for the wolves. The kill will feed the pack for several days but then they will have to resume the chase. At the frozen ends of our planet the struggle for survival never eases. South of the tree line, the winters are shorter, so trees grow faster and taller and forests begin to appear.