Pronghorn population dynamics and habitat connectivity in the Texas Panhandle

Date

2015-05

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Abstract

Pronghorn (Antilocapra americana) in Texas are assessed every year by the Texas Parks and Wildlife Department (TPWD), via aerial survey, to determine population size, spatial distribution, and harvest recommendations. Delineated herd units in the Panhandle/High Plains wildlife district (District 2) form the basic spatial unit of the TPWD’s pronghorn population assessment and harvest management goals. To determine the impact of anthropogenic and climatic factors on pronghorn population growth and distribution in District 2, I analyzed pronghorn population dynamics by assessing the population-level effects of hunter-harvest and precipitation on pronghorn population size via a multivariate analysis of covariance (MANCOVA) and a canonical discriminant function analysis (CDFA). I then evaluated pronghorn distribution by generating a presence-only spatial model of suitable habitat for pronghorn in District 2 in the MAXENT modeling environment using the following environmental variables: land cover, precipitation, vegetation greenness, distance to agriculture, distance to woodland, and distance to water. Lastly, I evaluated habitat connectivity within District 2 via CIRCUITSCAPE using the habitat suitability model as the primary input. I found that pronghorn populations vary significantly between herd units, especially herd units with larger population sizes. Precipitation and harvest, however, had a minimal effect on pronghorn populations. Additionally, very little highly suitable habitat remains in District 2, and the biggest risk to pronghorn habitat is woodland encroachment. Habitat is most connected in the northern-most portion of the Distirct 2, but connectivity is restricted by major roadways, which may isolate some pronghorn populations. In District 2, pronghorn populations experience minimal hunting pressure and a tolerance to changes in precipitation levels. Pronghorn habitat quality and connectivity, however, may become limiting factors for pronghorn in the future. Ensuring that suitable pronghorn habitat is conserved will assist in maintaining healthy pronghorn populations in District 2 as will the mitigation of barriers to pronghorn movement.

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Keywords

Pronghorn, Antilocapra Americana, Texas Panhandle, Habitat Suitability, Population Dynamics, Habitat Connectivity, Circuitscape, Maxent

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