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Distribution and abundance of tree voles in the northern Coast Ranges of Oregon.

ABSTRACT--We sampled 86 randomly selected survey plots to evaluate the distribution and abundance of Red Tree Voles (Arborimus longicaudus) on the Tillamook and Clatsop State Forests in the northern Coast Ranges of Oregon in 2011-2013. We conducted surveys by visually searching for tree vole nests while walking along 500 m of transect in each plot. Trees with potential nest structures were climbed to determine if the structures were tree vole nests. We found tree vole nests in only 4 random plots, all of which were located near the coast, at the western edge of the Tillamook State Forest. Of 33 tree vole nests located, 20 (61%) were in old forests ([greater than or equal to] 80 y old), and 13 (39%) were in 1 plot in a young forest that was 65 y old. We concluded that tree voles were absent from most of the Tillamook and Clatsop State Forests, probably due to the fact that most of the area was either logged or burned in the early 1900s, and subsequently intensively managed on short rotations. We also suggest that remnant stands of old forest on Bureau of Land Management and state lands are acting as source populations from which tree voles populate adjacent young forests. Cuttings found in nests provided evidence that most of the voles were feeding on needles of Western Hemlock (Tsuga heterophylla) or Sitka Spruce (Picea sitchensis).

Key words: Arborimus albipes, Arborimus longicaudus, Arceuthobium, Clatsop State Forest, Coast Ranges, dwarf mistletoe, line transect surveys, Oregon, Red Tree Vole, Tillamook Burn, Tillamook State Forest, White-footed Vole

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In 2011, the US Fish and Wildlife Service concluded that the Red Tree Vole (Arborimus longicaudus) warranted listing as a threatened or endangered distinct population segment in the Oregon Coast Range north of the Siuslaw River (USFWS 2011). However, the USFWS did not develop a proposed listing rule for the Red Tree Vole because other species had priority. The USFWS finding that the species warranted listing was based on evidence that tree voles were uncommon or absent in the Oregon Coast Ranges (Franklin and Dyrness 1973) north of the Siuslaw River and were susceptible to habitat loss from timber harvest (USFWS 2011). However, the USFWS also emphasized that surveys for tree voles had been largely focused on federal lands and that most state and private lands in the Coast Range of northwest Oregon had never been surveyed to determine whether Red Tree Voles were present. This made it difficult to assess the status of the species in much of the northern Coast Range. In 2011-2013, we conducted a survey to determine if tree voles were present on the Tillamook and Clatsop State Forests in northwestern Oregon. This region includes the northern periphery of the range of the Red Tree Vole in the Coast Range of Oregon. Our motivation for conducting these surveys was to resolve uncertainty about the distribution and abundance of tree voles in the northern Oregon Coast Range and to plan ahead for the likelihood that federal and state land managers will be pressed to provide more quantitative data on the distribution of tree voles in future assessments. Our primary objectives were to determine where tree voles occurred on state forest lands and what kinds of forests they occurred in.

METHODS

Study Area

Tillamook and Clatsop State Forests (Fig. 1) are characterized by a maritime climate, with cool, wet winters and warm, dry summers (Franklin and Dyrness 1973). The 204,000-ha area is largely mountainous and covered by forests of Douglas-fir (Pseudotsuga menziesii) in inland areas and forests of Western Hemlock (Tsuga heterophylla), Sitka Spruce (Picea sitchensis), and Red Alder (Alrius rubra) closer to the coast. Red Alder is an early-seral dominant on many sites, often forming nearly pure stands. Although Tillamook and Clatsop State Forests are both covered primarily by young forests, the management history of the 2 forests differs somewhat. Much of the area within the Tillamook State Forest burned 1 or more times during a series of 4 large human-caused fires that occurred in 1933-1951. Collectively referred to as the "Tillamook Burn", those fires destroyed approximately 143,000 ha of forest, much of which was old forest (Fig. 1; Highsmith and Beh 1952; Wells 1999). The Tillamook Burn fires were subsequently followed by extensive salvage logging and clear-cutting of the remaining forests in 1934-1960. The combination of fire, logging, and intensive silviculture on the burned areas produced a landscape that is now dominated by a mosaic of young forests and recent clear-cuts (Fig. 2; Highsmith and Beh 1952; Heinrichs 1983). The Clatsop State Forest consists of lands that were privately owned when the old-growth and mature forests that covered that area were largely removed by clear-cut logging in 1920-1940. Clatsop and Columbia Counties eventually deeded the cutover lands to the state of Oregon when the previous owners failed to pay taxes after logging the old forests (ODF 2010). At the time of our survey, old forests (80 to 250 y old) on the Clatsop and Tillamook State Forests were present in less than 4% of the study area (Fig. 2), and were mostly concentrated along the western edge of the region that burned during the Tillamook Burn fires (Fig. 3). The remnant stands of old forest were growing on areas that had never been harvested and were primarily the result of natural regeneration on areas that burned in the 1800s or early 1900s. There were only a few small parcels of federal lands within the study area (Fig. 1), and forests on virtually all of the state-owned lands were managed on relatively short rotations (40-80 y), with a primary emphasis on timber production (ODF 2010).

We used a stand inventory map from the Oregon Department of Forestry to determine ownership boundaries and forest age within the study area (Fig. 1, Fig. 2). The map consisted of a 2010 Geographic Information System (GIS) polygon shape file in which stand ages were estimated based on multiple sources, including on-the-ground inventories, photo interpretation, and growth-ring increment samples.

Sample Selection and Survey Methods

We used ArcGIS (ESRI, Redlands, CA) and Hawth's generate random points tool (http:// www.spatialecology.com/htools/tooldesc.php) to generate a random sample of 100 survey plots in the Tillamook and Clatsop State Forests. Age distribution of forest stands in which the randomly selected plots were located included 95 young stands (0 to 79 y old) and 5 mature or old-growth stands (80 to 250 y old). Our goal was to survey >80 of the randomly selected plots, assuming that some plots would be inaccessible due to road closures, dangerous terrain, or snow. Random plots were sampled regardless of forest age. Because there were so few old forests in the initial random sample, Oregon Department of Forestry biologists were concerned that we might overlook the presence of remnant vole populations in old forests. Therefore, we selected a 2nd random sample of 10 plots in forests [greater than or equal to] 80 y old. Our objective was to survey all 10 of the latter plots, but because of time constraints we were only able to survey 4 of them.

Surveys of random plots were conducted during September-February by walking along transects while visually searching for nests in the forest canopy. Transect design consisted of 5 parallel 100-m transects (corrected for slope) that were 50 m apart (Fig. 4). Slope corrections were calculated by estimating the average slope with a clinometer and adjusting transect length such that the horizontal distance covered by each transect was 100 m. The middle transect was centered on the randomly selected coordinates at the center of the plot and transects were laid out so that they were approximately parallel to the main slope aspect at the center of the plot (Fig. 4). Each plot was placed so that trees in the plot were all approximately the same age (same year of origin). In 41 cases in which randomly selected plots were near a boundary between 2 different-age stands, we moved plot centers slightly so that transects fell entirely among trees that were the same age as the trees at the randomly selected plot center. In 5 cases in which plot centers fell on extremely steep, snow-covered slopes that were deemed unsafe to survey, we moved the plot centers so that they fell in the same forest age-class, but on safer ground. To accommodate odd-shaped stands, transects were jittered to fit, as long as they were 50 m apart and parallel to each other. Two surveyors conducted the transect layout and surveys concurrently by searching for nests while pulling a 50-m tape along the predetermined compass bearing. All visible structures that looked like nests were considered potential nests. When potential nests were detected, surveyors measured the horizontal distance to the potential nest tree perpendicular to the transect. With the exception of 1 plot, potential nest trees were climbed to inspect nests on the day of the survey or within a week after the survey. The exception was a plot in which the road washed out and we could not get back to inspect potential nests until 5 wk after the survey. Tree vole nests were identified based on the presence of fecal pellets, resin ducts, debarked twigs, or fresh cuttings (Benson and Borell 1931; Clifton 1960; Maser 1966). Most (86%) tree vole nests were probed with a stiff wire or fingers to determine if they were occupied (Swingle and others 2004). Tree vole nests were assigned to 1 of 4 categories, depending on sign observed at the nest, as follows: (1) occupied--tree vole observed; (2) probably occupied--nest not probed, but intact with very fresh green cuttings present; (3) recently occupied--nest probed, no vole detected, green cuttings or green resin ducts present, but slightly desiccated; (4) old nest old cuttings, resin ducts, debarked twigs, or fecal pellets present.

Data Analysis

Our original objective was to use distance sampling methods to estimate the density of tree vole nests within different forest age-classes on the study area (Program DISTANCE; Thomas and others 2010). However, the number of nest detections was so small that precise estimates of density were not possible. Therefore, we summarized the data using simple comparisons of the number and percentage of survey plots with and without detections of tree vole nests. We also quantified survey effort as the number of person-hours spent conducting surveys and climbing trees to examine nests (Forsman and others 2009).

RESULTS

We surveyed 86 plots, including 82 of the original random sample and 4 of the random sample of old forest plots (Fig. 3, Appendix). The total number of potential nest structures located during the survey was 163. This included 119 structures detected from transects and 44 nests located while we were climbing trees or hiking in areas that were in or adjacent to transects. We physically examined 156 (96%) of these structures. The 7 structures not examined included 3 in trees deemed unsafe to climb and 4 that had disintegrated when we returned to climb trees. Of the 156 structures examined, 33 were Red Tree Vole nests, 80 were either Northern Flying Squirrel (Glaucomys sabrinus) or Douglas' Squirrel (Tamiasciurus douglasii) nests, 2 were White-footed Vole (A. albipes) nests, 3 were Deer Mouse (Peromyscus maniculatus) nests, 1 was a Bushytailed Woodrat (Neotoma cinerea) nest, 11 were bird nests, and 26 were debris platforms, clumps of moss, or dwarf mistletoe (Arceuthobium spp.) brooms. The 2 White-footed Vole nests were identified based on the presence of freshly harvested Red Alder leaves on top of the nests, and 1 of the nests also had a few greenish fecal pellets (Forsman and Swingle 2006).

Tree vole nests were detected in 4 (5%) of the 86 plots surveyed, including 1 plot in the original random sample and 3 plots in the additional random sample of old forest stands (Appendix). Of the plots with tree vole nests, 3 were in old forests that were 90 to 125 y old and 1 was in a 65-y-old forest that was located approximately 150 m from a 140-y-old forest. The 4 plots with tree vole nests were all located on the western edge of the Tillamook State Forest outside the areas that burned during the Tillamook Burn fires (Fig. 3).

Of the 33 tree vole nests detected, 8 were detected from transects during initial surveys, and 25 were located after initial surveys when we were climbing trees to inspect structures detected from transects or hiking in areas that were in or adjacent to transects (Appendix). Of the 33 tree vole nests, 6 (18%) were occupied or likely occupied and 27 (82%) were unoccupied nests. Of the 4 plots with tree vole nests, 2 had [greater than or equal to] 1 nests that were occupied or likely occupied by tree voles, and 2 had only old, unoccupied nests. The number of tree vole nests located per person-hour of survey effort was 0.02.

With the exception of 3 nests in a single old-growth Douglas-fir, all of the tree vole nests that we located were in Western Hemlock (n = 16) or Sitka Spruce (n = 14). Of the 33 tree vole nests, 5 were on branch whorls or single limbs, 5 were in tree cavities, 6 were in broken tree tops, 6 were wedged between forked trunks, and 11 were in dwarf mistletoe brooms. Based on 18 nests with recently harvested cuttings, we concluded that most of the tree voles were feeding primarily on Western Hemlock, although there were 4 nests that contained a mixture of Western Hemlock and Sitka Spruce cuttings, and 1 nest that contained an approximately equal mix of cuttings from Douglas-fir and Western Hemlock. It was unclear if the voles with 2 species of cuttings in their nests were feeding on both species or were feeding on 1 species and using the other as nest material.

DISCUSSION

Based on our survey and other recent surveys on federal, state, and private lands in the northern Coast Ranges of Oregon (Forsman and others 2008, 2012, in prep; USDA FS 2011; USDI BLM 2011), we concluded that tree voles were largely absent from most of the 4-county region in the northwest corner of Oregon, including most of the Clatsop and Tillamook State Forests. Within this region, tree voles appear to be present only in scattered locations along the coast, up to about 15 km inland, and north to Tillamook Head and Saddle Mountain (Fig. 5). If tree voles were ever present further north or further inland in this region, they appear to have been largely eliminated by fire, logging, and the almost complete conversion to a forest landscape covered by intensively managed young forests. Unfortunately, there is little information on the historical distribution of tree voles in much of northwest Oregon, so there is no way to determine how much of this region was occupied by tree voles prior to the conversion to a landscape dominated by young forest. The small amount of evidence that is available suggests that tree voles likely occurred throughout much of the northern Coast Ranges prior to European settlement (Hubbard 1940; Clifton 1960; Verts and Carraway 1998; Forsman and others 2004, in prep.).

There are some historical records that indicate that tree voles were at one time fairly common and widespread in the coastal forests west of the Tillamook and Clatsop State Forests. For example, Walker (1928, 1930) collected a number of tree voles on Cape Lookout and Cape Meares and a logger (D Bake) collected 98 tree voles while harvesting old-growth and mature forests in Tillamook and Lincoln Counties in 1966-1977 (Forsman and Swingle 2010). Another logger (R Brown), collected a tree vole near Saddle Mountain in 1967 (University of Puget Sound Slater Museum Specimen PSM23927), and Forsman and others (2004) found remains of 2 tree voles in pellets collected from Northern Spotted Owls (Strix occidentalis camina) near Jewell in Clatsop County. Our survey, and other surveys that we have conducted in state parks in the coastal forests of northwest Oregon (Forsman and others 2008), lead us to conclude that tree voles are still widely distributed in the region west of the Tillamook and Clatsop State Forests, but the number and distribution of occupied nests found in those areas during recent surveys suggest that densities are low and that remnant populations are mostly isolated in or adjacent to patches of old forest (Fig. 5).

Because some tree vole nests will go undetected during ground-based surveys (Swingle 2005), it is possible that we underestimated the proportion of survey plots with tree vole nests. Even if some nests were missed, however, we think it highly unlikely that no nests would be found on an entire survey plot if voles were present in an area (false negative). Because of this uncertainty, however, we think that additional studies are needed to evaluate detection probabilities of tree vole nests based on ground surveys in different forest age-classes. Such studies will almost certainly require climbing large samples of randomly selected trees in areas where tree voles are present.

Tree voles in the Sitka Spruce Zone (Franklin and Dyrness 1973) of northwest Oregon feed primarily on Western Hemlock and Sitka Spruce, and the resin ducts in their nests differ from resin ducts in nests of tree voles that feed on Douglas-fir. Voles feeding on Western Hemlock eat the outer edges of the needle and discard the center of the needle where the single resin duct is located (Clifton 1960; Kelsey and other 2009). Though our experience is limited, we have not found any resin ducts of Sitka Spruce in nests with Sitka Spruce cuttings. Apparently, tree voles do not remove the discontinuous resin ducts from Sitka Spruce or just eat the portion of the spruce needle that does not contain resin ducts (Kelsey and others 2009). Because nests of tree voles that feed on Sitka Spruce may not contain resin ducts, tree climbers that examine such nests will have to rely on other evidence that the nest is a tree vole nest, such as debarked twigs, fecal pellets, and small spruce cuttings.

Of the tree vole nests we located, 39% were in a young forest that was 65 y old. This result deserves several comments. First, the only young-forest plot in which we found vole nests was located 150 m from old forests. This, and many other cases in which we have found tree vole nests in young forests adjacent to old forests, leads us to hypothesize that old forests act as population sources for recolonization of adjacent young stands. Second, tree vole nests are probably more detectable in young forests than in old forests (Swingle 2005), especially in our study area, where old trees typically had numerous cavities and dwarf mistletoe brooms, and heavy accumulations of mosses and lichens that made it difficult to detect nests without climbing every tree. Thus, readers should use caution in comparing the proportion of nests found in young and old forests because those numbers are likely biased by unequal detection probabilities. Third, the vast majority of young forests that we examined had no evidence of occupancy by tree voles. Whether this deficit was due to silvicultural treatments or distance from remnant source populations of tree voles, or both, was unclear, but it does suggest that most young forests on the study area did not provide suitable habitat for tree voles.

In contrast to our results, there is considerable evidence that tree voles occur at low to moderate densities in some young forests in other regions of western Oregon and California (Maser 1966; Thompson and Diller 2002; Swingle 2005; Forsman and others 2009). Thus, we think that the almost complete absence of tree voles in most of the Tillamook and Clatsop State Forests may represent the extreme condition in which virtually all old forests were removed by fire and logging across a very large area and then followed by the almost complete conversion to a regime of intensive silviculture of young forests. The latter scenario has been the norm on non-federal lands in northwest Oregon for the last century, and is unlikely to change.

Our initial objective in this study was to use a distance sampling approach to estimate the density of tree voles in different forest age-classes on the Clatsop and Tillamook State Forests. This proved to be not very informative because the number of vole nests detected was zero in 95% of our plots, and even in stands with the most nests only a few nests were detected from transects. It did not require complex statistical methods and tenuous modeling assumptions to reach the obvious conclusion that tree vole density was zero in most of the Clatsop and Tillamook State Forests. Despite this result, we think that distance sampling methods may still be useful for estimating densities of tree voles in areas where tree voles are more abundant. Alternatively, researchers might forgo estimates of density entirely and use presence-absence data from multiple surveys to estimate occupancy rates of tree voles in different forest types. Neither of these alternatives will be cheap or easy.

APPENDIX. Nest detections in randomly selected survey plots on the
Tillamook and Clatsop State Forests, Oregon, 2011-2013. Data were
subdivided by the most recent species that occupied the nest.
Incidental nests found in or adjacent to the random plots while
climbing trees and searching off-transect are listed in parentheses.
Codes for nest types are: ARLO = Red Tree Vole (Arborimus
longicaudus); ARAL = White-footed Vole (Arborimus albipes); SQRL =
Douglas' Squirrel (Tamiasciurus douglasii) or Northern Flying
Squirrel (Glaucomys sabrinus); NECI = Bushy-tailed Woodrat (Neotoma
cinerea); PEMA = Deer Mouse (Peromyscus maniculatus).

                                             Number of nests
                                          detected, subdivided
                                                 by type
                              UTM         Stand
Location                coordinates (1)    age     ARLO    ARAL

Granite Creek           448759 5060089      52    0         0
Miami River             437147 5052624      57    0         0
Cook Creek              441825 5060982      39    0         0
NF Wilson               458119 5052073      46    0         0
McPherson Creek         442440 5062061      47    0         0
Strum Creek             467541 5087273      21    0         1
Big Creek               463680 5101139      53    0         0
Sam Downs Creek         444762 5044689      55    0         0
Hollywood               450919 5030104      41    0         0
Murphy Camp             461404 5026365      54    0         0
Sager Creek             469766 5090274      84    0         0
Elliott Creek           469758 5048199      57    0         0
Belding Creek           460110 5061072      45    0         0
Scoggins Creek          477177 5042555      85    0         0
Diamond Creek           437174 5050734      66    0         0
Fawcett Creek           439422 5026016      31    0         0
Knots Creek             464644 5106915       2    0         0
Mutt Peak               444158 5046842      40    0         0
George Creek            445043 5041131      55    0         1
Spaur Creek             458953 5042436      63    0         0
Lost Creek              445904 5063267      45    0         0
Kilchis River           438477 5048523      70    0         0
Cochran                 466982 5060467      21    0         0
Power House Road        437806 5051482      57    0         0
Timber                  473931 5066949      68    0         0
Keenig Creek            451835 5043671      46    0         0
Phipps Creek            461434 5040983      57    0         0
Cedar Butte             448128 5047236      48    0         0
Garibaldi               431942 5046060       2    0         0
Buick Canyon            450015 5063014      62    0         0
Bradwood                464586 5116264      28    0         0
Fishhawk Creek          454468 5090313      54    0         0
Upper Sager             470895 5089242       7    0         0
Idiot Creek             466722 5053595      53    0         0
Hopirvhome              448925 5072445      63    0         0
Fox Creek Ridge         456697 5039449      57    0         0
Windy Point             446409 5035870      58    0         0
Quarry Road             458033 5032174      60    0         0
Beaver Eddy             448796 5068878      65    0         0
NF Salmonberry          460868 5063511      50    0         0
Elkhom Headwaters       461120 5025913      54    0         0
Smith Creek             446433 5039527      55    0         0
Isler Creek             478702 5048399      60    0         0
Gales Headwaters        469903 5058879      71    0         0
EF Cook Creek           449032 5057700       0    0         0
Wolf Creek Grade        465840 5058787      71    0         0
Barney Reservoir        468239 5031735      58    0         0
Section 10 Road Spur    468412 5066873      21    0         0
Kerry Road              468518 5103208      63    0         0
Military Creek Road     466214 5079009      71    0         0
Step Creek              476786 5058665      60    0         0
Bateman Creek           478088 5051980      62    0         0
John Day River          442390 5111353       3    0         0
Nehalem River           446921 5065523      60    0         0
Mudge Loop              495842 5088177      23    0         0
Sunday Creek            472475 5038093      45    0         0
Green Mountain          444099 5097431       8    0         0
SF Trask River          452016 5024555      46    0         0
Crystal Creek           435663 5057184      65    2 (11)    0
Olson Creek             469436 5072881       0    0         0
McGregor Road           468693 5072895      62    0         0
Headquarters Grade      460375 5021397      60    0         0
Mesabi Creek            456062 5024849      50    0         0
Trailover Road          461758 5095734      54    0         0
Bauer Dam               478820 5056179      55    0         0
Lake Tahoe              453283 5020741      41    0         0
Fall Creek              438205 5065155      70    0         0
North Lousignont        472889 5066324      68    0         0
Stage Road              466358 5048840      57    0         0
Wildcat Mountain        479544 5056755      66    0         0
Little Clatskanie       497830 5087855     110    0         0
County Line Road        438844 5069654      37    0         0
Rackheap Ridge          437420 5067131      38    0         0
NF Cronin Creek         453827 5069306     100    0         0
Acey Creek              436572 5069395      40    0         0
Burma Road              451202 5067135      60    0         0
Blowout Ridge           446044 5043459       2    0         0
Williamsport Road       438196 5113005       2    0         0
Tunnel Creek            456341 5064925      32    0         0
Pipeline Road           441691 5111671      39    0         0
Helloff Grade           442480 5067675      80    0         0
Whitney Creek           441355 5048895      44    0         0
Little SF Kilchis (2)   439644 5043192     125    1 (5)     0
Doty Ridge (2)          436139 5044151      84    0         0
Rackheap Creek (2)      437783 5068514     100    3 (2)     0
Tillamook Ridge (2)     438665 5038861      90    2 (7)     0

Totals                                            8 (25)    2

                         Number of nests detected,
                             subdivided by type

Location                SQRL      BIRD   NECI   PEMA

Granite Creek            2          1     0      0
Miami River              0          0     0      0
Cook Creek               0          0     0      0
NF Wilson                0          0     0      0
McPherson Creek          0          0     0      0
Strum Creek              5 (3)      1     0      0
Big Creek                3          0     0      0
Sam Downs Creek          2 (1)      1     0      1
Hollywood                0          0     0      0
Murphy Camp              0          0     0      0
Sager Creek              4 (1)      0     0      1
Elliott Creek            2          1     0      0
Belding Creek            1 (1)      0     0      0
Scoggins Creek           1          0     0      0
Diamond Creek            2          0     0      0
Fawcett Creek            3          0     0      0
Knots Creek              0          0     0      0
Mutt Peak                0          0     0      0
George Creek             0          0     0      0
Spaur Creek              0          0     0      0
Lost Creek               0          0     0      0
Kilchis River            0          0     0      0
Cochran                  1 (1)      0     0      0
Power House Road         1          0     0      0
Timber                   0          0     0      0
Keenig Creek             2          0     0      0
Phipps Creek             0          0     0      0
Cedar Butte              1          0     0      0
Garibaldi                0          0     0      0
Buick Canyon             1          0     0      0
Bradwood                 0          0     0      0
Fishhawk Creek           3 (2)      1     0      0
Upper Sager              2          0     0      0
Idiot Creek              1          0     0      0
Hopirvhome               0          0     0      0
Fox Creek Ridge          2          1     0      0
Windy Point              0          0     0      0
Quarry Road              0          0     0      0
Beaver Eddy              2 (4)      0     0      0
NF Salmonberry           1          0     0      1
Elkhom Headwaters        0          0     0      0
Smith Creek              0          0     0      0
Isler Creek              0          0     0      0
Gales Headwaters         0          0     0      0
EF Cook Creek            0          0     0      0
Wolf Creek Grade         0          0     0      0
Barney Reservoir         0          0     0      0
Section 10 Road Spur     3          0     0      0
Kerry Road               0          0     0      0
Military Creek Road      0          0     0      0
Step Creek               1          0     0      0
Bateman Creek            0          0     0      0
John Day River           0          0     0      0
Nehalem River            0          0     0      0
Mudge Loop               2          3     0      0
Sunday Creek             0          0     0      0
Green Mountain           0          0     0      0
SF Trask River           0          0     0      0
Crystal Creek            0 (1)      2     0      0
Olson Creek              0          0     0      0
McGregor Road            0          0     0      0
Headquarters Grade       0          0     0      0
Mesabi Creek             0          0     0      0
Trailover Road           0          0     0      0
Bauer Dam                0          0     0      0
Lake Tahoe               0          0     0      0
Fall Creek               0          0     0      0
North Lousignont         1 (1)      0     1      0
Stage Road               0          0     0      0
Wildcat Mountain         0          0     0      0
Little Clatskanie        0          0     0      0
County Line Road         3          0     0      0
Rackheap Ridge           0          0     0      0
NF Cronin Creek          3          0     0      0
Acey Creek               1          0     0      0
Burma Road               0          0     0      0
Blowout Ridge            0          0     0      0
Williamsport Road        0          0     0      0
Tunnel Creek             1          0     0      0
Pipeline Road            0          0     0      0
Helloff Grade            0          0     0      0
Whitney Creek            0          0     0      0
Little SF Kilchis (2)    3 (1)      0     0      0
Doty Ridge (2)           0          0     0      0
Rackheap Creek (2)       0 (3)      0     0      0
Tillamook Ridge (2)      1          0     0      0

Totals                  61 (19)    11     1      3

(1) Universal Transverse Mercator Zone 10 coordinates at the center
of the survey plot (North American 1927 datum).

(2) Plots from the random sample of old forests.


ACKNOWLEDGMENTS

We thank C Smith, E Marcy, N Stumpf, H Harrison, K Skinner, J Johnson, B Moore, R Zilli, J Brandt, and F Lertora at the Oregon Department of Forestry for their help with maps and logistics. R Davis at the US Forest Service, Region 6, provided crucial GIS support. For their help with access across private lands we thank C Olson of Longview Timber Company, S Sweeney of Stimson Lumber Company, and T Tompkins of the Weyerhaeuser Company. Funding and in-kind support for this study was provided by the USDA Forest Service, USDI Bureau of Land Management, and Oregon State University.

LITERATURE CITED

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CLIFTON PL. 1960. Biology and life history of the Dusky Tree Mouse Phenacomys silvicola (Howell) [thesis]. Walla Walla, WA: Walla Walla College. 140 p.

FORSMAN ED, SWINGLE JK. 2006. White-footed Voles living in arboreal nests. Northwest Science 80:308-310.

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Submitted 22 January 2014, accepted 24 September 2014. Corresponding editor: Denim Jochimsen.

AMY L PRICE (1), JASON S MOWDY, AND JAMES K SWINGLE

Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331 USA

ERIC D FORSMAN

US Department of Agriculture, Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR 97331 USA

(1) Present Address: Bureau of Land Management, Grants Pass Field Office, 2164 Spaulding Ave., Grants Pass, OR 97526, USA; a_price@hotmail.com

* Unpublished
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Author:Price, Amy L.; Mowdy, Jason S.; Swingle, James K.; Forsman, Eric D.
Publication:Northwestern Naturalist: A Journal of Vertebrate Biology
Article Type:Report
Geographic Code:1USA
Date:Mar 22, 2015
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