Influences of abiotic and biotic habitat characteristics on pika occupancy in select regions of the Gallatin National Forest, Montana

Abstract

This research project explores how several abiotic and biotic habitat characteristics influence occupancy probabilities of the North American pika, Ochotona princeps within select regions of the Gallatin National Forest. Pikas are possible indicator species for climate change, as they are obligatory talus dwellers found in alpine and subalpine ecosystems, and are extremely sensitive to high temperatures. Slope, aspect, elevation, talus field dimensions, and mean boulder size likely influence how pikas experience ambient temperatures within specific habitat sites and consequently may influence occupancy probabilities. In addition, vegetation diversity and abundance may also influence the likelihood of a talus field being occupied by pikas. I investigated the relationship between abiotic and biotic habitat site characteristics and pika occupancy. I visited three sites within the Gallatin National Forest: Beehive Basin, Portal Creek, and Hyalite Canyon during the summer and fall of 2014. I surveyed 28 talus fields, quantifying a suite of habitat variables and determining pika occupancy of each site. The results of this study indicate that slope, aspect, and elevation were the strongest predictors of pika occupancy, whereas solar insolation, talus field area, mean boulder size, and distance to nearest neighbor were of less importance. Additionally, vegetation type and abundance did not prove statistically significant as a predictor of pika occupancy. Broadly speaking, pika occupancy within the Gallatin National Forest will likely depend on specific combinations of local abiotic and biotic habitat attributes.