Testing the forage preference of the American pika (Ochotona princeps) for use in connectivity corridors in the Washington Cascades

摘要

One of the aims of the Snoqualmie Pass East Project (SPEP) in the Cascades of central Washington is to construct nearly 30 wildlife crossing structures along a 15-mile stretch of Interstate-90. American pikas (Ochotona princeps) are being monitored for the SPEP because they have specific habitat requirements and are poor dispersers. Making the crossing structures “pika-friendly” will encourage these low-mobility animals to use the structures. Recent research suggests that the presence of quality vegetation may help pika populations avoid declines and extirpations, so planting suitable forage within and adjacent to the crossings will be essential. During the summer and fall of 2015, we completed 70 cafeteria-style preference experiments using 10 forage species that were common in pika-occupied habitats. In these trials, pikas were given equal forging access to 5-6 species at the same time. The results of these trials were analyzed using the Jacobs’’ selectivity index, Hotelling’s T2 tests, and one-sample t-tests. Douglas fir (Pseudotsuga menziesii), Sitka alder (Alnus viridis), willow (Salix spp.), and black cottonwood (Populus balsamifera trichocarpa) were the most selected species, and were recommended for planting in the upcoming crossing structures. Samples of each of the tested plant species were also analyzed for nutritional components and some plant secondary metabolites. Linear regression was used to evaluate which plant components influenced pika forage preference. Pikas selected for plants that contained either alkaloids or high levels of tannins. However, when both alkaloids and high levels of tannins occurred within the same plant, forage preference declined.