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Bison Research at Ordway Prairie
The Closing of the Rut
August 10, 2007 Update

Bison bulls wallowing at Ordway Prairie, SD
Bison wallowing, Ordway Prairie Preserve
Photo courtesy of Gustavus Adolphus College research team

After a month and a half of intense competition for mating rights, the rut is finally coming to a close. We have seen numerous bulls rise to the top only to fall once again as new competition arises. During the rut, as they focus solely on activities associated with mating; their physical condition often declines, as they spend more energy than they take in. By the end of the rut they are ready for some much-needed rest and recuperation.

At this time in the rut, most of the “dominant” bulls have left the herd, allowing the lowest-ranking bulls a chance at mating with the few remaining cows coming into estrous (heat). Occasionally, a once-dominant bull such as “Hipspot” will re-enter the herd only to be chased out by a bull that was once his inferior. Why does Hipspot not meet this challenge with the same aggression as he would have previously?

Because only a few cows have not to come into estrous, we presume Hipspot’s nonaggressive behavior may be an effort to reduce his risk of injury and save energy for the coming winter months.

This year’s rut has proved to be quite different. Over the previous three years of this research project, two bulls held the top spot, one dominant early in the rut and the other taking his place later. With more than 10 bulls vying for mating rights, the hierarchy was not as simple this year. Five to six bulls held the top spot at various times. We believe this changing dynamic allows for a greater amount of genetic diversity in the next generation of calves.

Next year holds the possibility of being as exciting as this year. Three bulls that did not show much authority this year will be at the age to challenge some of our top bulls. This can only mean more bellowing, more wallowing and more fights as they work out whom nature has intended to hold that coveted top spot…

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