Comparison of Fecal, Rumen and Utilization Methods for Ascertaining Pronghorn Diets

Abstract

Fourteen male pronghorn (Antilocapra americana), two in each of seven spring and summer months, were killed to obtain rumen and fecal matter for comparing methods of determining diets. They came from a herd confined to the Desert Experimental Range in southwestern Utah. Animals were killed only after they had completed their early morning grazing period. Plant material was removed from the rumens and rectums, fresh feces were collected from the feeding site, and forage utilization and production estimates were made there. Diets as indicated by the four data sources-rumen, intestinal feces, site feces, and utilization-varied with individual animals from close to little agreement, a not unexpected result in view of food availability and selection. Fewer plant species were identified by fecal analysis than were found in the rumen; even fewer species were recorded by utilization estimates. This indicates that fecal analysis may be less accurate than rumen data but more so than those based on plant utilization. Validation tests of the fecal method conducted with mule deer (Odocoileus hemionus) fed known diets showed substantial differences with individual species in the amounts fed and the amounts indicated by fecal analysis. Only in the case of the single grass species fed was there close agreement; browse and forb species differed greatly.