Impacts of Pronghorn Grazing on Winter Wheat in Colorado

Abstract

Wheat growers in Colorado believe pronghorns (Antilocapra americana) grazing on winter wheat (Triticum aestivum) reduce wheat yields. Thus, we investigated the effects of pronghorn grazing on winter wheat yields to evaluate effects. Free-ranging pronghorns used wheat fields from November through April, but abandoned them by early May. Pronghorns appeared to use green winter wheat forage when its nutritional value exceeded that of native forages. Forage quality of winter wheat forage was high autumn through spring (Oct-May) when nutrition of native forage was low. Pronghorns abandoned winter wheat fields in mid-late spring apparently at a time when nutritional value of native forages was increasing and wheat forage was decreasing. Captive, hand-reared pronghorns were grazed in pastures to impose 3 distinct grazing treatments (early winter, late winter, and all winter) throughout the period when free-ranging pronghorns occupied winter wheat fields. Although pronghorns removed measurable amounts of green wheat, this removal did not reduce (P = 0.19) grain yields. We believe nutritional dynamics of winter wheat and native forages induce a grazing pattern that shifts pronghorn use from wheat fields to native pastures before winter wheat is vulnerable to grazing damage. Our data suggest reductions in pronghorn populations to alleviate perceived wheat damage are unnecessary.