The University of Arizona

Vegetation Cover and Forb Responses to Cattle Exclusion: Implications for Pronghorn

Matthew R. Loeser, Sharon D. Mezulis, Thomas D. Sisk, Tad C. Theimer


Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understand the effects of cattle grazing, we studied the potential hiding cover provided by standing live and dead herbaceous matter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P 1⁄4 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P 1⁄4 0.105) or 25 m (P 1⁄4 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P 1⁄4 0.036), but no differences were observed in 2002 (P 1⁄4 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.

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