The polar fomentin has a prey/predator relationship with an animal called the doseal. The polar fomentin eats the doseal. When they arrived at the taiga the doseal adapted and the polar fomentin did too. The doseal had to develop legs so that it could run from the polar fomentin. So while the doseal developed legs through the generations the polar fomentin had to develop longer and stronger legs too so it was able to eat it. Now because of this relationship both animals have very long legs.