Comparative Food habits and Range use of Pronghorn and Cattle in the Texas Panhandle

Date

1982-08

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Publisher

Texas Tech University

Abstract

Pronghorn in the Texas Panhandle occur on scattered, isolated islands of uncultivated prairie. With changing land use patterns in the Panhandle, there is some concern about the ability of pronghorn to cope with habitat alterations. This study was designed: (1) to determine the plant species most commonly eaten by sympatric pronghorn and cattle in 3 study areas, (2) to assess the availability and degree of utilization of the vegetation in each study area, and (3) to assess the dietary flexibility and overlap between pronghorn and cattle, and compatibility of pronghorn with livestock grazing within and between 3 habitats. Three vegetatively different areas were chosen for study, ranging from the open prairie grassland of the High Plains, to the mesquite (Prosopis glandulosa) savanna of the Rolling Plains, to the shinnery oak (Quercus havardii) Sandhills.

Forbs made up the bulk of the pronghorn diet (68%-90%) on all sites and showed little seasonal variation, regardless of different forb availabilities among study areas. Grass use was minor and ranged from l%-4% of the annual diet among study areas. Use of shrubs occurred only when forbs were not available (4%-22% of the diet among areas). The percentage that each food plant occurred in the diet was divided by the percentage it occurred on the range to yield a Selection Index (SI). Although flexibility in pronghorn diets was not seen, almost all food plants were selected with Si's greater than 1.0, indicating a high degree of selectivity.

Cattle ate mainly grass on all areas (46%-63%). Forbs constituted 12%-31% of the annual diet among areas and shrub use was 2%-20%. Cattle were less selective in feeding than pronghorn in that many of the major dietary items had Si's at or near 1.0.

Dietary overlap of pronghorn and cattle varied among areas and ranged from 10%-37%. Data suggested that dietary overlap among areas varied inversely with the quality of pronghorn habitat. Habitat vii selection data indicated pronghorn used open, gently rolling areas, and significant preference/avoidance for different vegetation types was expressed only on the Rolling Plains where vegetation types were highly varied. Factors affecting the use of different pastures by pronghorn were similar among areas; vegetative composition appeared to be more important than the presence or absence of cattle. Thus, pronghorn range use data indicated that separation from cattle was not maintained spatially (via pasture or vegetation type use), but maintained through selective food habits and grazing. Competition for forage with cattle was not as important as quality of habitat in determining pronghorn success in the Texas Panhandle. Vlll

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