Title

Multi-Scale Habitat Relationships for the Great Basin Collared Lizard in Southwestern Idaho

Publication Date

11-2004

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Major Advisor

James C. Munger

Abstract

Great Basin Collared Lizard habitat in the intermountain northwest has been qualitatively characterized as dry rocky-washes, boulder-strewn hillsides, rock piles, and talus slopes where vegetation is sparse. To provide a quantitative description of Great Basin Collared Lizard habitat, I examined habitat relationships at three spatial scales for Great Basin Collared Lizard use sites and random sites in southwestern Idaho. A 1m2 quadrat was used to collect habitat data at the microhabitat scale. At the habitat scale, line intercept and belt transects were used to collect cover and density data for habitat variables. GIS data were used to examine landscape scale variables for all sites.

At both the microhabitat and habitat scales, total rock cover was significantly (P < 0.0001) greater at lizard sites (56.6% and 28.5%, respectively) compared to random sites (5.3% and 5.9%, respectively) while total shrub and herbaceous cover were greater at random sites. When individual variables were analyzed, a similar pattern was observed with all four categories of rock (cobble, melon, boulder, and bedrock) having significantly greater cover at lizard sites compared to random sites at both the microhabitat and habitat scales (P < 0.0001). Individual shrub cover at the microhabitat scale was consistently higher at random sites. However, at the habitat scale, two shrub species (Atriplex cansescens and Tetrademia glabrata) had significantly higher mean cover at lizard sites (0.88% 1.51%, respectively) compared to random sites (0.10% and 0.16% respectively). Shrub density for these shrubs was also greater at lizard sites. However, their frequency of occurrence was low <40%) at lizard sites for either species.

Coordinates for each of the random and lizard sites sampled were used to explore landscape-scale relationships with existing GIS data. Great Basin Collared Lizard locations occurred in only four habitats categories (salt-desert shrub, big sagebrush, perennial grassland, and shrub-steppe annual grassland), which account for 94% of the available GAP II habitat within the study area. No significant difference was found between the proportions of habitats used by Great Basin Collared lizards compared to the proportions of habitats available in the study area (P = 0.5928). Using slope and aspect values from 10m Digital Elevation Models, lizards sites were found on significantly (P = <0.0001) steeper slopes (x̄ = 13.96%) and they occurred more frequently in the 181-270° (SW) aspect class (P < 0.0001). The density of melon-sized rocks and boulders was much greater at lizard sites (1.16/m2 and 0.27/m2, respectively) compared to random sites (0.44/m2 and 0.07/m2, respectively). Unfortunately, the rock component was not well represented in the landscape scale data limiting the comparison among scales. At the microhabitat and habitat scales, rocks, particularly boulder-sized rocks were the most important feature. While some shrub species were identified as being statistically significant, the biological significance is less clear. Current landscape-scale maps focusing on vegetation classification may have limited use for predicting Great Basin Collared Lizard habitat within the study area since vegetation had limited cover and density at lizard sites. However, landscape models that focus on slope and aspect may be useful. Additional GIS modeling should include soils or geology to increase the predictive power of the model.

Files over 30MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS