HABITAT SELECTION AND CURRENT DISTRIBUTION OF THE PYGMY RABBIT IN NEVADA AND CALIFORNIA, USA

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Abstract

We surveyed the historic range of pygmy rabbits (Brachylagus idahoensis) in Nevada and California using infrared-triggered cameras to determine the species' current distribution and habitat selection. Areas with potential habitat were mapped using geographical information system coverages for elevation, big sagebrush (Artemisia tridentata) vegetation, and loamy soils. Within this region random sites and field-selected sites with sagebrush islands (prominent clusters of sagebrush higher than the surrounding sagebrush) were surveyed for the presence of pygmy rabbits. Sites were measured for sagebrush height, surrounding sagebrush height, sagebrush cover, and soil composition. Likelihood of pygmy rabbit occupancy at a site increased with the presence of sagebrush islands, increasing sagebrush cover, and decreasing surrounding sagebrush height. Additionally, we surveyed 1,394 other sites across the species' historic range and found current activity of pygmy rabbits at 258 of these sites. We measured sagebrush cover, sagebrush height, understory stem density, and presence or absence of cottontail rabbits, jackrabbits, red soils, cheatgrass, and rodent burrows at 454 sites. We used 80% of the data to create a logistic regression model. The top-ranked Akaike's information criterion-selected model suggested that likelihood of pygmy rabbit occupancy at a site increased with increasing sagebrush cover, decreasing understory stem density, absence of cottontails, absence of reddish soils, absence of cheatgrass, and absence of rodent burrows. This model showed a 79% accuracy rate in predicting occupancy within the remaining data. Current populations of pygmy rabbits were found throughout all of the species' historic range in Nevada and the southern portion of its range in California.

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