Livestock Grazing Effects on Pronghorn Preferred Forbs during the Winter in the Trans-Pecos, Texas

Leanna S. Morin, Justin T. French, Carlos E. Gonzalez, Louis A. Harveson, and Shawn S. Gray (TPWD)

Pronghorn (Antilocapra americana) is a native North American ungulate found in semi-arid landscapes, including grasslands, shrub-steppes, and deserts. Historically, pronghorn coexisted and co-evolved with bison (Bison bison). Today, pronghorn continue to cohabit with bison in some areas but more often share regions with domestic cattle (Bos taurus) in western states. In the Trans-Pecos region of Texas, pronghorn and cattle commonly reside in the same range. Previous studies reveal that bison interference in pronghorn habitat is rare, and bison foraging exposes vegetation that pronghorn can more easily find and consume. However, the effects of cattle grazing on forb communities are not thoroughly understood.

Pronghorn populations in the Trans-Pecos have declined significantly in the last two decades. Since 2011, Texas Parks and Wildlife Department and partners have implemented strategies to mitigate pronghorn loss through translocations and habitat improvements. As part of these efforts, cattle grazing may be manipulated to further improve pronghorn forage quality and quantity, but is poorly studied. Therefore, a better understanding of livestock grazing effects on forb communities is significant for pronghorn restoration efforts.

To investigate cattle grazing effects on forb communities, we will focus on three livestock grazing systems. Using a 3.280 ft Daubenmire frame, samples will be taken from 100 random 3.280 ft vegetation plots in a 2120.905 ac continuously grazed pasture. We will also take samples from 150 random 3.280 ft vegetation plots in an 8673.399 ac pasture that is subdivided into 35 paddocks that are rotationally grazed for approximately two weeks during the eight-month dormant season. Finally, we will take samples from 50 random 3.280 ft vegetation plots in 10 non-grazed 0.988 ac enclosures located randomly throughout the continuous and rotational pastures.

Each vegetation sample will be collected in January 2021 during the cool season, as this is the most limiting time for forage availability during the year, and then again in September during the warm-wet season of 2021 and 2022, when resources are most abundant. We hypothesize that forb abundance and quality will be lower in the continuous than in the rotational and non-grazed pastures. Understanding the response of forb communities to livestock grazing systems may allow managers to adapt grazing practices to maximize the efficacy of actions to enhance pronghorn habitat.

Funding sources: San Antonio Livestock Exposition and Texas Parks and Wildlife Department.