In September through mid-October the elk go through the "rut," their mating season. A bull will claim a harem of cows and calves as his for breeding, he aggressively defends them from rival males. It is amazing to hear them bugle, a loud, shrill sound that attracts females and alerts other bulls of their presence. Elk spotters are reminded by signs and rangers to keep their distance from the elk, preferably near a vehicle in case the "testosterone-charged" bulls decide to take out their aggression on the spectators! We saw this bull chase away some younger, "spike" bulls. According to the rangers, this bull had just taken over the herd at the beginning of October, so he probably missed out on his chance to breed.