JACKSON, Wyo. — The rut season in the Greater Yellowstone Ecosystem is currently underway for some of the region’s largest mammals. Expect bugles and bellows as fall descends on the valley from bison, elk and moose.
Wildlife viewing can be exciting during this time with males clashing and sparring but also more dangerous because these animals can be especially aggressive and harder to predict.
The National Park Service (NPS) requires all visitors to remain at least 25 yards away from bison, elk, bighorn sheep, deer, moose and coyotes and at least 100 yards from bears and wolves.
Bison
The bison rut lasts each year from June to September, with most of the activity occurring between July and August.
According to the NPS, once a bull finds a receptive female, he will form a tending bond to keep other bulls ways from her. During these tending bonds, the bull demonstrates intolerance for all other group members through a variety of bellowing, wallowing and threat displays. Unlike other species, that form harems—animal groups consisting of one male and multiple females—male bison will remain part of the large group during the rut except for these temporary tending bonds.
“It is documented that higher male copulation rates are associated with higher social dominance. Females are more willing to copulate with larger, more dominant males than with smaller males,” according to an NPS article.
Elk
From early September through October, bull elk can be heard bugling at twilight. This sound is made to advertise their fitness to cow elk and to show off to other bulls. Elk are most active before sunrise and after sunset but will bugle throughout the night as well. The rut can begin as early as late August and can continue into early November, according to the NPS.
During the rut, cows, calves and yearlings form harems with one or two mature bulls. The harem is formed by bugles from the bulls, trying to attract cows to mate with. The rut begins in September and lasts through October, with peak rut attributed to Sept. 21.
Moose
Moose are solitary creatures for most of the year, except during the mating season, which runs from late September into early October.
“After growing out their antlers all season, males are ready to display. While sparring does happen, males normally display to each other by parading around, shaking their antlers and showing off their size,” said Grand Teton National Park in a social media post. “If the smaller male knows he won’t win a fight, he will bow out before the two come to blows.”
During the rut, females will group together and bulls will fight with each other in order to gain mating rights. As a result, bull moose can be very aggressive during this time with anything they perceive to be a threat to them.
