“The bison are in the rut, their mating season in Yellowstone National Park. These are displays of dominance.”

These Yellowstone motorists were treated to some serious roadside vocalizations by a few of the parks largest residents.  During mating season male “bellows” have been compared as to revving up an old Chevy truck.  It is believed that these bellows announce the male’s presence and establish herd dominance. The interval of these sounds increase during male-male competitions or when they are trying to find mates. According to The National Park Service, scientific studies indicate that the acoustic qualities such as the frequency, length, and volume of the bellows demonstrate which males are more dominant, and therefore, a better mate to females. These vocalizations may reveal information about the male’s competitive ability, physiological quality and condition, and sexual receptivity…in other words, the bellows denote fitness-related information. Fascinating.