Territorial species, like gray wolves living in Yellowstone National Park, will often fight if they encounter a neighboring group. Observational research over the course of 20 years has allowed scientists in Yellowstone to examine the roles of each individual in a wolf pack during these fights over territory and resources. They have discovered that old wolves are the most important in pack versus pack fights as the experience and leadership provided by an old wolf often allows a pack to win even if they are outnumbered.