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Structure and movements of a community of small mammals along a powerline right-of-way in subalpine coniferous forest.

Linear disturbances such as roads and powerline right-of-ways may influence abundance and species composition of communities of small mammals (Adams and Geis, 1983; Carthew et al., 2009). Although there have been studies on communities of small mammals near forest-field edges (e.g., Manson et al., 2001; Nickel et al., 2003; Hopkins and Kennedy, 2004) and in forest-clearcuts (Kirkland, 1990; Fisher and Wilkinson, 2005), relatively few have addressed powerline right-of-ways. Powerline rights-of-ways often have abrupt edges and differ from forest-field edges and clearcuts in being narrow and linear and maintained at an early stage of succession (Chasko and Gates, 1982). The effect of powerline right-of-ways on communities of small mammals, therefore, may be different from that of clearcuts and forest-field edges.

The early successional habitats of powerline right-of-ways often provide habitats for species not present in adjacent forest (Schreiber and Graves, 1977; Johnson et al., 1979; Goosem and Marsh, 1997; King and byers, 2002). Previous studies of small mammals in powerline right-of-ways have revealed that species richness and diversity are higher in right-of-ways and edges compared to surrounding forests (Quarles, 1978; Johnson et al., 1979; Gates, 1991). Higher diversity often is a result of an influx of species adapted to early successional habitats that do not occur in surrounding forests (Goosem and Marsh, 1997). Although powerline right-of-ways can increase diversity, they also may form a barrier to movements of forest-adapted species (Schreiber and Graves, 1977; Quarles, 1978; Ladino, 1980; Gates, 1991). The specific effect a powerline right-of-way has on movements of small mammals depends on width of the right-of-way, plants within the right-of-way (Gates, 1991), and, perhaps, perceptual ability of species under consideration (Zollner and Lima, 1997).

Previous studies of communities of small mammals along powerline right-of-ways have occurred in eastern deciduous forests (Schreiber and Graves, 1977; Quarles, 1978; Johnson et al., 1979; Ladino, 1980) and tropical rainforests (Goldingay and whelan, 1997; Goosem and Marsh, 1997). However, response of small mammals to powerline right-of-ways in these ecosystems may not be representative of other ecosystems, such as montane coniferous forests. in our study, we compared species composition, density, and movement patterns within and along a powerline right-of-way to that of an undisturbed subalpine coniferous forest in the southern Rocky Mountains. we hypothesized that diversity and abundance would be higher on right-of-ways than in undisturbed forest. in particular, we expected the right-of-way and adjacent forest to be dominated by North American deermice (Peromyscus maniculatus). in addition, we hypothesized that the right-of-way would be a barrier to movements of southern red-backed voles (Myodes gapperi), but not least chipmunks (Tamias minimus) or North American deermice.

MATERIALS AND METHODS--Six sites were selected within a subalpine coniferous forest in Roosevelt-Arapahoe National Forest near Idaho Springs, Clear Creek County, Colorado (ca. 39[degrees]42'N, 105[degrees]39'W). Selection of sites was based on successional stage of the right-of-way, accessibility, and permission from the United States Forest Service. Sites were ca. 3,140-3,320 m in elevation and faced east-northeast. Three sites contained a 40-m-wide powerline right-of-way constructed in the late 1960s (powerline sites), whereas the three others were in undisturbed, subalpine coniferous forest (control sites). Maintenance in the right-of-way included periodic tree-cutting to provide clearance for two 230-kV transmission lines (T. Wooley, pers. comm.). A 3-m-wide trail for off-highway vehicles was within the right-of-way at powerline sites 1 and 2.

Vegetation in the right-of-way included bearberry (Arctostaphylos uva-ursi), quaking aspen (Populus tremuloides), lodgepole pine (Pinus contorta), common lupine (Lupinus argenteus), and several graminoids. All trees were <9 m tall. Edge habitats adjacent to the right-of-way contained mature conifers with a subcanopy of quaking aspens, lodgepole pines, subalpine firs (Abies lasiocarpa), and Engelmann spruces (Picea engelmannii). Ground cover was various graminoids and arnica (Arnica cordifolia). Vegetation at control sites was typical of mature, subalpine coniferous forest consisting of a mixture of mature Engelmann spruces and subalpine firs (Fitzgerald et al., 1994); the forest was less dense and had less ground cover than at powerline sites. Small streams occurred within or adjacent to powerline sites 1 and 2 and control sites 1 and 2.

During our study (June-July 2000), mean daily temperature was slightly above average (1975-1999, mean = 11.7[degrees]C; 2000, mean = 12.8[degrees]C) and average precipitation was below average (1975-1999, mean = 38.6 mm; 2000, mean = 30.7 mm). Climatic data were from Dillon, Summit County, Colorado (United States Historical Climatology Network), which was at 2,763 m elevation and ca. 35 km from the sites studied.

In June and July of 2000, we placed 130 Sherman live traps (7.6 by 9.0 by 23.0 cm; H. B. Sherman Traps, Tallahassee, Florida) on a 10-by-13 grid at 15-m intervals at each site (2.43 ha). Each powerline site was separated by [greater than or equal to] 150 m along the right-of-way, and each control site was [greater than or equal to] 300 m from the right-of-way. Grids were set square to the right-of-way at each site using a magnetic compass. At powerline sites, three traplines were in the right-of-way (0-15 m from center of right-of-way), two were in edge habitats on each side of the right-of-way (15-30 m from boundary of right-of-way), and three were in forested habitats on each side of the right-of-way (45-75 m from boundary of right-of-way). Although control sites were in undisturbed forest, we labeled traplines in control grids as being in either right-of-way, edge, or forested habitats as per powerline grids for the purpose of comparison to powerline sites.

Traps were baited with a mixture of peanut butter and rolled oats that was wrapped in wax paper and suspended above the treadle as described by Stout and Sonenshine (1973). Because bright moonlight influences activity of small mammals (Price et al., 1984), trapping never occurred within 3 days of a full moon. Each trapping session was 13 days comprised of 3 days of prebaiting (trap baited and locked open), 5 days of mark-recapture, and 5 days of mark-translocation, for a total of 1,300 trap-nights at each of the six sites. one powerline and one control site were trapped simultaneously during each 13-day session. individuals were marked uniquely by toe-clipping and released at site of capture. Species, mass, sex, and location were recorded for each individual. To avoid potential impact on the endangered Preble's jumping mouse (Zapus hudsonicus preblei), all captured jumping mice were identified to species and then released immediately without being marked.

Voucher specimens were collected on the last day of each trapping session and were deposited in the Sternberg Museum of Natural History. Because of the difficulty of distinguishing between the least chipmunk (T. minimus), Colorado chipmunk (T. quadrivittatus), and uinta chipmunk (T. umbrinus), any of which could occur in the study area (Bergstrom and Hoffmann, 1991), the baculum of voucher specimens was excised and identified using morphological features (Lechleitner, 1969). Identification of female chipmunks was problematic; therefore, females were assigned the same species as males from a given location. Procedures for capturing and handling small mammals followed guidelines of the American Society of Mammalogists (Animal Care and Use Committee, 1998).

We calculated species richness and a Chao1 (bias-corrected) species-richness estimator for each site using program Estimates (R. K. Colwell, http://purl.oclc.org/estimates). The Chao1 model was used because it incorporates rare species (singletons and doubletons) into its estimate and is well suited to data that include several species of low abundance (Chao, 1987). when encountered, the number of western jumping mice at a site was assumed to be three, providing a conservative estimate of diversity at each site. When encountered, two to five western jumping mice often were captured on the same day; therefore, it is likely that three or more individuals were present at the site. A Chao-Jaccard estimated-abundance-similarity index also was calculated using Estimates to determine similarity in species composition between powerline and control sites. The Chao-Jaccard index is a probability-based index that is less biased than the traditional Jaccard index because it compensates for the effect of unseen shared species (Chao et al., 2005).

We estimated mean abundance of southern red-backed voles, North American deermice, and least chipmunks for each site using the closed-capture function in program MARK (White and Burnham, 1999). We estimated density of these species at each site by dividing the estimate of abundance by the effective area of the trapping grid as determined by mean-maximum-distance moved by individuals of each species (Wilson and Anderson, 1985). Mean-maximum-distance moved was calculated for nontranslocated individuals during the 10-day trapping period. Naive density was calculated when there was insufficient data to estimate abundance or mean-maximum-distance moved. Average daily probabilities of capture for southern red-backed voles, North American deermice, and least chipmunks were 0.28, 0.37, and 0.29, respectively; thus, most individuals at each site should have been captured at least once during the 10-day trapping session. Densities of southern red-backed voles, North American deermice, and least chipmunks were compared between powerline and control sites with a one-way analysis of variance (ANOVA).

Habitat preference (right-of-way, edge, forest) at powerline sites was determined using a chi-square test of independence. observed values were calculated by pooling number of captures in each habitat during the mark-recapture period. Expected values were weighted by sampling effort within each habitat. Habitat preference also was calculated for control sites (right-of-way, edge, forest) for the purpose of comparison with powerline sites.

We assessed natural movements of nontranslocated southern red-backed voles, North American deermice, and least chipmunks to determine whether individuals crossed the right-of-way. These movements were compared to movements of individuals at control sites. We also assessed whether the right-of-way was a barrier to movements by comparing homing success of individuals translocated across the right-of-way to those translocated across the right-of-way at control sites. During mark-translocation, individuals captured in edge and forested habitats at powerline sites were moved directly across the right-of-way to edge habitats on the opposite side of the right-of-way as described by Schreiber and Graves (1977). At control sites, individuals captured in edge and forested habitats were moved directly across the right-of-way in the same manner as at powerline sites. individuals were never translocated >110 m from site of capture (mean = 75-83 m for each species). The maximum distance of translocation was within the range of movements exhibited during natural movements of each species. Homing success of translocated individuals was pooled within powerline and control sites and compared using a Fisher's Exact-probability test. only individuals that were recaptured after translocation were included in the analysis.

We used data from captured, nontranslocated southern red-backed voles and North American deermice at powerline sites to assess whether direction of movements in edge and forested habitats were random in reference to the right-of-way. Movements between captures were standardized such that 0[degrees] represented movement directly toward the right-of-way and 180[degrees] was directly away from the right-of-way. We used a Rayleigh's test for circular statistics on pooled data from all three powerline sites to determine whether direction of movements in edge and forested habitats was random following Batschelet (1981). We performed separate Rayleigh's tests for North American deermouse captured in edge and forested habitats to determine whether direction of movements differed with distance from the right-of-way. Southern red-backed voles were pooled across edge and forested habitats due to a small sample. Directions of movements for southern red-backed voles were bimodal and were, therefore, drawn from an axial distribution (Batschelet, 1981). Rayleigh's tests were performed using program PAST ([empty set]. Hammer et al., http://folk.uio.no/ohammer/past/index. html). All other statistical analyses were performed in STATISTICA 6.1 (StatSoft, Tulsa, Oklahoma).

RESULTS--During a total of 7,800 trap-nights (powerline sites, 3,900; control sites, 3,900), we captured 181 individuals representing 10 species at powerline sites and 128 individuals of 9 species at control sites (Table 1). The North American deermouse was the most prevalent species at powerline sites, accounting for 33.1% of individuals captured at powerline sites. The southern red-backed vole was the most common species at control sites, accounting for 43.0% of individuals captured at control sites. The least chipmunk, montane vole (Microtus montanus), and red squirrel (Tamiasciurus hudsonicus) were more prevalent at powerline sites. Despite variation in rates of capture among species at powerline and control sites, a Chao-Jaccard estimated-abundancesimilarity index (0.933 [+ or -] 0 SE) suggested that powerline and control sites were similar in species composition.

The masked shrew (Sorex cinereus) was captured significantly more often in forested habitats at powerline sites ([chi square] = 16.6, P < 0.001) but did not demonstrate any habitat preference at control sites ([chi square] = 0.22, P = 0.894). North American deermice did not exhibit habitat preference at powerline ([chi square] = 1.46, P= 0.482) or control sites ([chi square] = 1.26, P = 0.532). Captures of southern redbacked vole were higher in forested habitats at powerline sites ([chi square] = 22.02, P < 0.001) and in forested habitats at control sites ([chi square] = 32.17, P < 0.001). Least chipmunks preferred the right-of-way ([chi square] = 11.93, P = 0.003) at powerline sites. There were not enough captures of least chipmunks to assess habitat preference at control sites.

Density of southern red-backed voles at control sites was more than twice that at powerline sites (ANOVA, [F.sub.1,4] = 19.04, P = 0.012, Table 2). Least chipmunks had a significantly greater density at powerline sites ([F.sub.1,3] = 12.96, P = 0.037), while density of North American deermice was not significantly different between sites ([F.sub.1,4] = 0.39, P = 0.570).

An adult male southern red-backed vole crossed the right-of-way at powerline site 2 during its natural movements (two crosses by one individual). At control sites, the right-of-way also was crossed during natural movements of southern red-backed voles (nine crosses by six individuals). However, when translocated across the right-of-way, southern red-backed voles at powerline sites were less likely to cross the right-of-way than individuals at control sites were to cross the right-of-way (Fisher's Exact test, P = 0.013). At control sites, 12 southern red-backed voles were translocated across the right-of-way and 10 of these individuals subsequently were recaptured on the side of original capture. At powerline sites, however, only one of six translocated southern red-backed voles was recaptured on the side of original capture.

During their natural movements, North American deermice readily crossed the right-of-way (13 crosses by nine individuals) and the right-of-way at control sites (four crosses by four individuals). After translocation, North American deermice readily crossed the right-of-way at control sites (Fisher's Exact test, P = 1.000). At control sites, 15 North American deermice were translocated across the right-of-way and 10 of them returned to the site where they were captured originally. At powerline sites, 31 individuals were translocated across the right-of-way and 19 were recaptured on the side where they were captured originally.

Least chipmunks crossed the right-of-way in their natural movements (four crosses by three individuals) and after translocation at powerline sites. There was no translocation of least chipmunks at control sites; thus, we were unable to compare homing success at powerline and control sites. At powerline sites, however, 13 least chipmunks were translocated across the right-of-way, nine of which returned to the side where they were captured originally.

Southern red-backed voles in edge and forested habitats at powerline sites exhibited significant directional movements parallel to the right-of-way (Rayleigh's test, P < 0.001, n = 15, mean direction of movement = 82.2[degrees]). North American deermice moved randomly in edge habitats adjacent to the right-of-way (P = 0.714, n = 21) but exhibited a significant directional movement toward the right-of-way in forested habitats (P < 0.001, n = 22, mean direction of movement = 353.5[degrees]).

DISCUSSION--Overall abundance of small mammals was greater at powerline sites than at control sites. There are several ecological factors that could result in this difference including an edge effect, higher ground cover, or greater abundance of seeds at powerline sites. Dense vegetation in powerline right-of-ways previously have been shown to benefit small mammals by providing runways and nesting sites (Johnson et al., 1979). Our results differ from Goldingay and Whelan (1997), who reported that abundance decreased along a powerline right-of-way in eucalyptus forests. The effect of the powerline right-of-way on abundance at our sites was similar to disturbances such as partially cut forests, clearcut forests (Kirkland, 1990; Fisher and Wilkinson, 2005), and ski runs (Hadley and Wilson, 2004a, 2004b).

Species richness was similar at powerline and control sites, and, based on a Chao-Jaccard similarity index, these sites also were similar in species composition. The greatest difference between powerline and control sites was relative abundance of southern red-backed voles, North American deermice, and least chipmunks. As expected, we captured more southern red-backed voles at control sites and greater numbers of North American deermice and least chipmunks at powerline sites.

Density of southern red-backed voles at control sites was more than twice that of powerline sites. The southern red-backed vole is a mature-forest species (Sekgororoane and Dilworth, 1995; Sullivan et al., 2001) that prefers habitats containing rotting logs, loose litter (Gunderson, 1959; Nordyke and Buskirk, 1991), and hypogeous ectomycorrhizal fungi (ure and Maser, 1982). it is common in mature lodgepole pine and mixed sprucefir forests (Fitzgerald et al., 1994) but may be rare in early successional habitats such as subalpine meadows (Brown, 1967), clearcuts (Ramirez and Hornocker, 1981; Martell, 1983; Walters, 1991), and ski runs (Hadley and Wilson, 2004a).

We were surprised that powerline sites did not have significantly higher density of North American deermice. However, a retrospective power analysis following the confidence-interval method of Steidl et al. (1997) suggested our results for density of North American deermouse were inconclusive. Assuming a 20% increase in density of North American deermice at powerline sites is biologically significant, the 95% confidence interval for density of North American deermice at powerline sites (CI, 2.07 [less than or equal to] 4.73 [less than or equal to] 6.32 individuals/ha) included the expected density (4.21 individuals/ha). Least chipmunks and North American deermice tend to be more abundant in disturbed habitats than in unbroken coniferous forests (Armstrong, 1977; Carey and Wilson, 2001; Hadley and Wilson, 2004a, 2004b). The open, early-successional habitats created by the powerline right-of-way likely favors increased abundance of least chipmunks and North American deermice.

Along powerline right-of-ways, small mammals generally are most abundant in species-specific habitats (Quarles, 1978; Johnson et al., 1979). In our study, southern red-backed voles were significantly more abundant within forested habitats at powerline sites. Although rate of capture may have increased in forested habitat due to greater distance from the right-of-way, the higher rate of capture in forested habitat at control sites suggests that availability of water also was a factor. Streams were more prevalent within forests at powerline sites and forested habitats within control sites, and captures of southern red-backed voles generally were within 30 m of water. This is not surprising given the high water requirements of southern red-backed voles (Getz, 1968; Merritt and Merritt, 1978) and their preference for mesic habitats (Orrock et al., 2000).

Although presence of riparian habitats may have influenced our results, we suggest that the right-of-way also had an effect on distribution and density of southern red-backed voles. For example, at powerline site 1, there was a stream running parallel to the grid alongside the right-of-way as well as the forested and edge habitats on each side of the right-of-way. At this site, all captures of southern red-backed voles were within forest and edge habitats near the stream, suggesting an avoidance of right-of-way habitat near the stream. in addition, there was no riparian habitat at powerline site 3 or control site 3, yet the density of southern red-backed voles was 224% greater at control site 3. Taken together, these data suggest that southern red-backed voles prefer forested habitats and avoid powerline right-of-ways.

Masked shrews also were more abundant within forested habitats at powerline sites, likely due to their preference for mesic habitats (Williams, 1955). For example, at powerline site 1, 8 of the 11 cinereus shrews were captured in forested habitats parallel to a stream. At powerline site 2, all 11 cinereus shrews were captured in forested habitats at the western edge of the trapping grid where there were two small streams. in contrast to southern red-backed voles, cinereus shrews did not exhibit any habitat preference at control sites. At control site 2, all seven shrews were captured near a stream. Although cinereus shrews may have been avoiding the right-of-way, previous research has shown this species to have no attraction to, or avoidance of, edge habitats (Sekgororoane and Dilworth, 1995). We do not believe our data support avoidance of the right-of-way by cinereus shrews. Rather, distribution of water on our trapping grids and lower abundance of shrews at control sites led to their preference for forested habitats at powerline sites.

Least chipmunks were significantly more abundant within the right-of-way at powerline sites. Given the affinity of this species for open habitats and general avoidance of closed coniferous forests (Vaughan, 1974; Fitzgerald et al., 1994), the right-of-way created an area of favorable habitats for least chipmunks.

Powerline right-of-ways can form a barrier to movements of small mammals (Schreiber and Graves, 1977; Quarles, 1978; Gates, 1991; Goosem and Marsh, 1997). The influence a right-of-way has on movements often depends on successional stage of the right-of-way, with early succession being a barrier to forest-dwelling species (Gates, 1991). At our study sites, the right-of-way was not a barrier to movements of North American deermice or least chipmunks. The fact that movements of North American deermice within forested habitats at powerline sites was biased toward the right-of-way suggests that North American deermice prefer to be near early successional habitats of the right-of-way. The right-of-way and adjacent edge may serve as suitable foraging habitats for North American deermice.

Although a male southern red-backed vole crossed the right-of-way in its natural movements, the few right-of-way crossings following translocation suggest the right-of-way formed at least a partial barrier to southern red-backed voles. The bias in movements of southern red-backed voles parallel to the right-of-way also suggested that the right-of-way formed a behavioral barrier to movements. our results are similar to those of Keinath and Hayward (2003), who reported that in the central Rocky Mountains, southern red-backed voles do not cross the boundary of forested habitats and regenerating clearcuts.

Although our study was limited to one season and suffers from a limited sample and the influence of riparian habitats, we believe that some general inferences can be made for management of small mammals along powerline right-of-ways. Retention of downed woody debris in ski runs benefits the southern red-backed vole (Hadley and Wilson, 2004b). We believe that retention of downed woody debris in powerline right-of-ways would provide refugia and reduce the impact of the right-of-way on abundance and movement of southern red-backed voles. Powerline right-of-ways may also impact higher trophic levels within subalpine forests. For example, powerline right-of-ways provide roosting habitats for predators such as red-tailed hawks (Buteo jamaicensis; Knight and Kawashima, 1993). Southern red-backed voles often are the most abundant small mammal in subalpine forests (Hayward and Hayward, 1995); thus, changes in their abundance may influence populations of predators. For example, southern red-backed voles are a favored prey item of martens (Martes americana; Sherburne and Bissonette, 1993). Least chipmunks are an important prey for northern goshawks (Accipiter gentilis Squires, 2000); thus, powerline right-of-ways may provide favorable foraging habitats. Additional research is necessary to understand the full impact that powerline right-of-ways have on communities of small mammals and how these changes may influence dynamics of food webs.

We thank R. Channell, G. Farley, S. Lima, W. Stark, D. Sparks, and M. Storm for comments on the manuscript. R. Storm provided assistance in the field, J. Boyles assisted with program MARK, R. Jean helped with program Estimates, and C. Booher translated the abstract.

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Submitted 22 June 2010. Accepted 21 June 2012.

Associate Editor was Jennifer K. Frey.

JONATHAN J. STORM * AND JERRY R. CHOATE

Department of Biological Sciences, Fort Hays State University, Hays, KS 67601 (JJS)

Sternberg Museum of Natural History, Fort Hays State University, Hays, KS 67601 (JRC)

Present address of JJS: Division of Natural Sciences and Engineering, University of South Carolina Upstate, Spartanburg, SC 29303

* Correspondent: jstorm@uscupstate.edu
TABLE 1--Number of individuals captured and diversity of the
community of small mammals at three sites that contained a 40-m-wide
powerline right-of-way and three control sites in undisturbed
forests in Roosevelt-Arapahoe National Forest near Idaho Springs,
Clear Creek County, Colorado. There was a total of 1,300 trap
nights at each site.

        Species                                Powerline

                                1            2           3       Total

Southern red-backed             4           12           10       26
  vole, Myodes gapperi
Montane vole, Microtus          2            4           0         6
  montanus
Ermine, Mustela erminea         0            0           0         0
Bushy-tailed woodrat,           0            1           0         1
  Neotoma cinerea
North American                 21           26           13       60
deermouse, Peromyscus
  maniculatus
Masked shrew, Sorex            11           11           6        28
  cinereus
Cinereus shrew, Sorex           2            5           4        11
  monticolus
American water shrew,           0            1           0         1
  Sorex palustris
Golden-mantled ground           0            0           0         0
squirrel, Spermophilus
lateralis
Least chipmunk, Tamias          7           16           9        32
  minimus
Red squirrel,                   0            0           10       10
  Tamiasciurus
  hudsonicus
Western jumping mouse,          3            3           0         6
  Zapus princeps
Total individuals              50           79           52       181
Species richness                7            9           6        10
Chao 1 [+ or -] 1 SE       7 [+ or -]   10 [+ or -]  6 [+ or -]
                              0.01          0.8         0.00

        Species                                Control

                               1            2            3        Total

Southern red-backed            16          23            16        55
  vole, Myodes gapperi
Montane vole, Microtus         0            1            0          1
  montanus
Ermine, Mustela erminea        0            0            1          1
Bushy-tailed woodrat,          0            0            0          0
  Neotoma cinerea
North American                 15          13            6         34
deermouse, Peromyscus
  maniculatus
Masked shrew, Sorex            0            7            10        17
  cinereus
Cinereus shrew, Sorex          0           11            4         15
  monticolus
American water shrew,          0            1            0          1
  Sorex palustris
Golden-mantled ground          0            0            1          1
squirrel, Spermophilus
lateralis
Least chipmunk, Tamias         0            1            2          3
  minimus
Red squirrel,                  0            0            0          0
  Tamiasciurus
  hudsonicus
Western jumping mouse,         0            0            0          0
  Zapus princeps
Total individuals              31          57            40        128
Species richness               2            7            7          9
Chao 1 [+ or -] 1 SE       2 [+ or -]  10 [+ or -]  7.5 [+ or -]
                              0.00        4.44          1.29

TABLE 2--Estimates of abundance and density (individuals/ha) with
standard errors (SEE) for the southern red-backed vole (Myodes
gapperi), North American deermouse (Peromyscus maniculatus), and
least chipmunk (Tamias minimus) at three sites that contained a
40-m-wide powerline right-of-way and three control sites in
undisturbed forest in Roosevelt-Arapahoe National Forest near Idaho
Springs, Clear Creek County, Colorado. Estimates of abundance are not
given at some sites due to few or no captures.

          Site             Abundance   SE    Density      SE

Southern red-backed vole
  Powerline 1                  -        -    1.65 (a)      -
  Powerline 2                12.0      0.0   2.49        0.44
  Powerline 3                10.1      1.3   2.03        0.55
  Control 1                  17.4      1.5   4.49        0.88
  Control 2                  25.0      2.8   4.58        0.69
  Control 3                  16.0      0.0   6.58 (a)      -
North American deermouse
  Powerline 1                25.0      5.1   6.32        1.49
  Powerline 2                26.0      0.0   5.80        0.64
  Powerline 3                13.0      0.0   2.07        0.25
  Control 1                  15.0      0.0   6.17 (a)     -
  Control 2                  13.0      0.0   3.04        0.45
  Control 3                   6.0      0.0   1.33        0.74
Least Chipmunk
  Powerline 1                 7.0      0.0   2.88 (a)     -
  Powerline 2                16.0      0.0   3.28        0.37
  Powerline 3                 9.0      0.0   1.85        0.44
  Control 1                    -        -    0.00         -
  Control 2                    -        -    0.41(a b)    -
  Control 3                    -        -    0.82 (a)     -

(a) Naive estimate of density due to limited captures or lack of
mean-maximum-distance moved.

(b) Only one individual was captured.
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Author:Storm, Jonathan J.; Choate, Jerry R.
Publication:Southwestern Naturalist
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Geographic Code:1USA
Date:Dec 1, 2012
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