Pygmy Rabbit (Brachylagus idahoensis) Habitat Selection: Does Sagebrush (Artemisiaspp.) Age Influence Selection?

Abstract

The pygmy rabbit (Brachylagus idahoensis) is a sagebrush (Artemisia spp.) obligate that depends on sagebrush habitats for food and cover throughout its life cycle. Invasive species, frequent fires, overgrazing, conversion of land to agriculture, energy development, and many other factors have contributed to recent declines in both quantity and quality of sagebrush habitats required by pygmy rabbits. Given declining availability of sagebrush, there is a need to identify characteristics of suitable pygmy rabbit habitat. Although habitat selection information exists from several western states, data is limited for pygmy rabbits in Utah at the extent of their range. We sampled 77 different habitat variables at occupied (n = 72) and unoccupied (n = 61) sites in Utah. We then used random forests to determine which variables best discriminated between occupied and unoccupied sites. We predicted that sites occupied by pygmy rabbits would have greater percentages of sagebrush, greater amounts of cover, and greater mean sagebrush age compared to unoccupied sites. Occupied sites had greater horizontal obscurity (measure of cover), occurred at higher elevations, had greater percent understory composed of sagebrush and other shrubs, and lower percent sagebrush decadence than unoccupied sites. Contrary to our predictions, sagebrush age at occupied sites was not an important variable and mean age did not differ by site type. We suggest managers use this information to help identify suitable pygmy rabbit habitats to further conservation of this imperiled lagomorph.