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77 fundamental principles to mitigation and management. The Great Basin of western Utah near Beaver, Utah (latitude approach for this study was to develop ecological principles 3816 N and longitude 11237 W), adjacent to Interstate 15 that have conceptual generality and that can be applied (I-15), a four-lane divided highway with an average of 16,015 broadly. The caveat of course is the necessity for gathering vehicles/day. Elevation ranged from 1,700 to 1,900 m (5,500 local, empirical data that will inform the programming, plan- to 6,300 ft). Vegetation cover was dominated by big sage- ning, design, and construction phases of building, upgrading, brush (Artemisia tridentata) with an occasional inclusion and maintaining roads. of pinyon pine (Pinus edulis) and juniper (Juniperus For this effort, sites characterized by natural vegetation osteosperma) trees. The road verge included sagebrush and located next to roads were selected and compared to sites grassy vegetation or was completely non-vegetated. The distant from the road. Indirect effects have been suggested to weather was characterized by below-freezing temperatures operate within 100 m of a road; however, as a precaution, we and snow cover during the winter and high temperatures designed our sampling protocol to detect changes that may during the summer. Maximum temperatures occasionally occur up to 600 m or more from the road. Small mammals exceeded 38C (100F) and minimum temperatures were have relatively small home ranges and limited mobility, and usually above 23C (10F), with annual mean temperature the research team expected that results should be evident of 8.6C (47.4F). Annual precipitation (in the form of rain within 600 m from the road. The research team measured and snow) was less than 305 mm (12 in.), and came prima- small-mammal species' presence or absence, composition, rily during winter, early spring, and late summer. Relative and relative abundance through trapping periods in the sum- humidity was very low and evaporation potential was high. mer months of 2004 and 2005. Prolonged periods of drought are frequent in the region. The In both Utah and British Columbia, the research team soil on the trapping sites was composed mainly of fine sand sampled at increasing distances from the road to address deposits with occasional volcanic rocky areas. Study sites these putative effects: were established in sagebrush-steppe vegetation along 20 mi (~32.2 km) of Interstate 15, centered on UTM (NAD27) X = If habitat quality is reduced near the roadway, the presence 354471 Y = 4248267. Small-mammal sampling was con- or absence, composition, and relative abundance of species ducted exclusively in sagebrush habitat on both sides of the is expected to change at increasing distances from the road. road (Figure 18). Because changes in sagebrush habitat were If there are edge buffer effects along the road, there is ex- detected along the road, the research team designated the dif- pected to be a zone close to the road where the presence, fering habitats A, B, and C. abundance, and composition of species will be dramati- Small mammals were live and lethal trapped from 30 May cally influenced. to 14 August in 2004 and from 17 June to 18 August in 2005. The trapping design was altered between the 2004 and 2005 field seasons to maximize the useful information gleaned. In Research Approach: Methods and Data 2004, trapping webs were used to assess road influence on The work for this segment was conducted in Utah and small-mammal communities. In 2005, the research team used British Columbia in two very different habitats. Utah is lo- trapping lines to compare the Utah results with the British Co- cated in the Intermountain West of the United States. The lumbia trapping scheme. During summer 2004, 12 transects study site was composed mainly of sagebrush (Artemisia spp.) were completed with 2 trapping webs per transect, for a total habitat, and the road verge (ROW) is largely non-vegetated. of 24 webs. The first trapping web was placed at 50 m (close) Conversely, the British Columbia site in Canada is heavily and the second at 400 m (distant) from the road (Figure 19). forested with a densely vegetated road verge. The research Each web was composed of eight segments extending 50 m team adapted its sampling scheme to maximize capture of outwards from a central point. Each segment had six trapping small mammals for these very different sites. The following stations of two traps each, located 5, 10, 20, 30, 40, and 50 m paragraphs describe how the field work was conducted in from center, with one trapping station located at the center of each site. The research team began work in Utah in 2004 as the web for a total of 98 traps [half lethal (snap) and half live part of an ongoing study and continued in 2005. In British (non-lethal)] per web and a total of 2,352 traps for the 24 Columbia, the research team conducted the field work dur- webs. During summer 2005, 3 trapping lines were placed par- ing summer 2005. allel to the road along each of 5 transects (Figure 19) for a total of 15 trapping lines. Lines were placed at increasing distances from the exclusion fence: at 0 m (close), 200 m (mid), and Utah 600 m (distant). Each line was 150 m in length and contained Permeability and small-mammal trapping. This study 30 traps total, for a total of 450 traps for the 15 trapping lines. was conducted in the high-elevation desert region of the The research team completed a total of 8,406 trap-nights. For

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78 Figure 18. Sagebrush habitat in southwestern Utah where small-mammal trapping was conducted. safety reasons, the ROW verge between the road edge and the For analysis, capture data was pooled in "close webs" and "dis- 2.4 m deer exclusion fence was not sampled because of very tant webs" because of the low number of animals sampled in high traffic volume. each web. Estimation was only possible for the most abundant All traps in both sampling schemes were baited with a mix- species (i.e., > 30 captured individuals per pooled database) or ture of horse grain and peanut butter, and checked on three for all small mammals combined. Density estimations in Dis- consecutive mornings and afternoons (lethal traps only). tance were obtained by every possible combination of models Upon capture, all animals were identified, sex determined, (uniform, half-normal, hazard, and negative exponential) and measured, marked, and released. Dead animals were removed adjustment terms (cosine, simple polynomial, and Hermite from the study site. polynomial). See Appendix F. Final model selection was based on Akaike's Information Criterion (AIC) value and on model Data analyses. Web-based data analysis for 2004 em- performance. Each dataset was used in its entirety without ployed a distance method described by Anderson et al.5 that truncation. Intervals used in Distance (0.0, 7.5, 15, 25, 35, and utilizes first capture locations for each individual and distance 45 m) were the midpoints between trap-stations. Resulting to the center of the web plot. The software program Distance densities in close and distant webs were tested for significant 4.140,41 was used to calculate densities and variance estimates. differences using Wald test. Close Distant 2004 2005 Close Mid Distant Figure 19. Schematic representation of sampling schemes in 2004 and 2005.

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79 Analysis for trapping line data in 2005 was conducted ROW was composed of a rough track, but no developed road using a closed population mark-recapture method in Pro- (Figure 20, right panel). Highway and transmission-line sam- gram MARK 4.3.243 Closure was assumed given that trapping pling was equally distributed within the trapping period. The occurred in a sufficiently brief interval, and the removals were most recent data for highway traffic volume was recorded in known and accounted for in the analysis.246 A Huggins Closed 2001, approximately 25 km south of the southernmost high- Capture estimator was applied to obtain abundance estimates way site. Traffic volume averaged 1,791vehicles/day annually, and the respective confidence intervals. Capture data was including a peak of 2,043 vehicles/day during July and August pooled in three groups representing increasing distances (S. Daniels, Ministry of Transportation, Cranbrook, British from the road (close, mid and distant). Estimates were ob- Columbia, unpublished data). Traffic volume along the trans- tained for the null and other models to represent variability mission line was essentially nil (estimated 1 to 5 vehicles/day in capture and recapture probabilities. Models that did not average on an annual basis; the research team saw <1 vehi- converge were discarded. Remaining models were selected cle/site/day of trapping or baiting). based on AIC value and averaged to obtain final estimates of Traps were placed on three transects: at 50 m, 300 m, and abundance. Differences in abundance estimates were tested 500 m distant from and paralleling the road. The research using Wald test. team consistently set the 50 m transect 20 m into the forest to The ShannonWiener diversity index (H) was used to standardize its distance from a change in habitat type. This compare community diversity at different distances from the placement resulted in an average distance of 49 m from the road.17 The index was calculated for each web or trapping line highway centerline, or 51 m from the transmission line cen- in all transects and tested for distance-related differences terline. Sites were not randomly selected. Rather, the research by the Wilcoxon paired-sample test for 2004 data and by team used 1:20,000 orthophotos and field inspections to locate Friedman's test for 2005 data.250 The least significance differ- all points along the transmission line. The study area had pre- ence (LSD) multiple-comparison test was used with 2005 dominantly mesic soils; continuous or nearly continuous for- data to determine if any pair of distances (close vs. mid; close est cover; and no minimal or major roads, large cut-blocks, vs. distant; mid vs. distant) was significantly different.218 significant habitat shifts, or other sampling sites within 600 m radius on at least one side of the ROW. An equal number of highway sites fitting the same criteria were selected. British Columbia Each transect was 150 m long and oriented parallel to the Permeability and small-mammal trapping. Field sites ROW (326 to 360). The research team established 16 trap were located in the Rocky Mountain Trench of southeastern stations per transect (10 m intervals), with two snap traps British Columbia at elevations of 830 to 1000 m, centered on (Snap-E Mousetrap, Kness Mfg. Co., Inc., Albia, Iowa) occu- 50.1 N by 115.8 W. Eight study sites were selected for each of pying each trap station (Figure 21). The research team used a two treatments (Figure 20): along a 30 km stretch of Highway grease gun to bait traps with a mix of peanut butter and rolled 93/95 (mean total ROW width 57 9 m SD, including 12 m oats, placed them unopened for 1 week, replaced the bait, and wide highway), and along 40 km of a high-voltage transmission left them unopened for an additional week (i.e., a 2-week pre- line (mean ROW width 62 8 m SD). The transmission-line bait). Then the traps were baited again, set for 2 nights, and Figure 20. Right-of-way types: Highway 93/95 (left) and high-voltage transmission line (right).