Arborimus Longicaudus Research Articles

Characterizing long‐term population conditions of the elusive red tree vole with dynamic individual‐based modeling

AbstractOld growth forests are declining globally, threatening dependent wildlife. Many arboreal old‐growth obligates, such as the threatened red tree vole, are difficult to monitor for changes in habitat occupancy, and abundance. Yet, conservation planning relies on this information to prevent population declines. We integrated a range of species, habitat, and landscape change information to develop a dynamic habitat‐population model. The spatial individual‐based model simulated dynamic patterns of occupancy that responded to annual habitat maps, describing 36 years of observed change. We simulated population dynamics and local movement to characterize changes in occupancy and abundance, and the capacity of remaining habitat to support red tree voles. Red tree vole redistribution patterns strongly corresponded to wildfire footprints and timber extraction locations. Population strongholds are likely to exist in clumped pockets of old‐growth forest that were unaffected by wildfire and in protected old forest reserves. However, the exact number and locations of local clusters remain uncertain. Simulated population losses occurred at different paces in different places, underscoring the need for recurring evaluation of population changes with field occupancy surveys and modeled evaluations that can anticipate potential connectivity and extirpation thresholds. This modeling approach was effective at leveraging existing information for a data‐light species to assess how historical changes to the quantity, quality, and configuration of habitat likely influenced the potential landscape capacity, species abundance, and distribution. Dynamic individual‐based modeling can benefit conservation planning for red tree vole and other reclusive forest species by providing biologically nuanced assessments of abundance and distribution. Such models can also project the long‐term benefits and impacts of spatially explicit land management plans.

Ecosystem Conditions That Influence the Viability of an Old-Forest Species with Limited Vagility: The Red Tree Vole

We evaluated ecosystem conditions known to influence the viability of a strictly arboreal species (the red tree vole, Arborimus longicaudus) endemic and historically distributed in the forests across the Coast Range, Cascades, and Klamath Mountains ecoregions in the Western United States of America. We found widespread reductions in ecosystem conditions needed to support the long-term viability of the red tree vole. This was particularly evident in the Coast Range where the weighted watershed index (WWI) was 26% of its historical value, and the current probability of maintaining viability departed the most from historical viability probabilities in ecoregions that were evaluated. In contrast, in the Cascades and Klamath Mountains, the WWI was 42% and 52% of their respective historical values, and the current probabilities of maintaining viability departed less from historical conditions than in the Coast Range. Habitat loss from timber harvest represented the most immediate threat in the Coast Range, while habitat loss from wildfires represented the most risk to the red tree vole in the Cascades and Klamath Mountains. Reducing the risks to the viability of the red tree vole will depend largely on the implementation of conservation practices designed to protect remaining habitat and restore degraded ecosystems in the Coast Range. However, the risk of large, high-severity wildfires will require the protection and increased resilience of existing ecosystems. Our results indicate that considerable adaptation to climate change will be required to conserve the red tree vole in the long term. Conservation may be accomplished by revising land and resource management plans to include standards and guidelines relevant to red tree vole management and persistence, the identification of priority areas for conservation and restoration, and in assessing how management alternatives influence ecosystem resiliency and red tree vole viability.

Timber harvest and wildfires drive long-term habitat dynamics for an arboreal rodent

Animals dependent on old, closed-canopy forests may be particularly sensitive to forest disturbances, such as timber harvest and high-severity fires, that may take centuries to recover from. Tracking habitat trends can provide broader context to conservation decisions, including the role of forest disturbance type. We assessed habitat dynamics across the range of the red tree vole (Arborimus longicaudus), a canopy-obligate rodent with low-mobility that typically occurs in old forests. We developed and applied a red tree vole habitat model to imagery data each year across 37 years (1986–2022). We quantified changes in habitat across four regions that differed by land ownership and dominant disturbance type. Overall, habitat declined 18 % since implementation of a major conservation initiative (1994–2022). Habitat change was highest in the northern coast (65 %) where timber harvest was the most common disturbance. Within interior regions, several large wildfires in the previous two decades correlated with a 15 % decline of habitat on federal lands, particularly at the northern range periphery where tree voles were already scarce due to historic disturbances. Recruitment of old forest and subsequent recolonization by red tree voles and other low mobility species after high-severity disturbance can take centuries whereas old forest loss can happen rapidly. Given their strong association with old forest, scarcity within historic disturbance footprints, and relatively limited geographic range, we anticipate red tree voles will remain a species of conservation concern.

Predator-prey interactions in the canopy.

Small mammal abundances are frequently limited by resource availability, but predators can exert strong lethal (mortality) and nonlethal (e.g., nest abandonment) limitations. Artificially increasing resource availability for uncommon small mammals provides a unique opportunity to examine predator–prey interactions. We used remote cameras to monitor 168 nest platforms placed in the live tree canopy (n = 23 young forest stands), primarily for arboreal red tree voles (tree voles; Arborimus longicaudus), over 3 years (n = 15,510 monitoring‐weeks). Tree voles frequently built nests and were detected 37% of monitoring‐weeks, whereas flying squirrels (Glaucomys oregonensis) built nests infrequently but were detected 45% of monitoring‐weeks. Most nest predators were detected infrequently (<1% of monitoring‐weeks) and were positively correlated with tree vole presence. Weasels (Mustela spp.) were highly effective predators of tree voles (n = 8 mortalities; 10% of detections) compared to owls (n = 1), flying squirrels (n = 2), and Steller's jays (n = 1). Tree vole activity decreased from 84.1 (95% confidence interval [CI]: 56.2, 111.9) detections/week 1‐week prior to a weasel detection to 4.7 detections/week (95% CI: 1.7, 7.8) 1‐week postdetection and remained low for at least 12 weeks. Interpretations of predator–prey interactions were highly sensitive to how we binned continuously collected data and model results from our finest bin width were biologically counter‐intuitive. Average annual survival of female tree voles was consistent with a previous study (0.14; 95% CI: −0.04 [0.01], 0.32) and high compared to many terrestrial voles. The relative infrequency of weasel detections and inefficiency of other predators did not provide strong support for the hypothesis that predation per se limited populations. Rather, predation pressure, by reducing occupancy of already scarce nest sites through mortality and nest abandonment, may contribute to long‐term local instability of tree vole populations in young forests. Additional monitoring would be needed to assess this hypothesis.

Tardigrades in the Forest Canopy: Associations with Red Tree Vole Nests in Southwest Oregon

Tardigrades live in many ecosystems, but local dispersal mechanisms and the influence of ecological gradients on tardigrade communities are not fully understood. Here we examine tardigrade communities in nests of the red tree vole (Arborimus longicaudus True), an arboreal mammal occupying the canopy of coniferous forests in western Oregon and northwestern California. We found 12 species of tardigrades from resin ducts sampled from 43 nests along a transect that spanned the east-west range of the red tree vole in southern Oregon. Tardigrade occurrence was more likely in larger trees and species numbers were significantly higher in areas that received more precipitation. At sites where they occurred, tardigrades were more abundant in red tree vole nests at greater heights within the forest canopy. Of the 12 species of tardigrades that were found, seven have not been previously reported in Oregon. Our results suggest that tardigrades in forest canopies in the Pacific Northwest are affected by regional precipitation gradients as well as local environmental variables, and that nest building by small mammals may facilitate dispersal of tardigrades within the forest canopy.

Age Distribution of Red Tree Voles in Northern Spotted Owl Pellets Estimated from Molar Tooth Development

We used molar measurements from 136 known-age red tree voles (Arborimus longicaudus) to develop regression models that could estimate tree vole age from skeletonized remains. The best regression included a quadratic structure of the ratio between two measurements, crown height and anterior height, and natural log-transformed age in days. The regression predicted that molar roots begin to develop at 40 days of age and that molar crowns are worn completely away at 1,177 days of age. We used the regression to estimate the age distribution of 1,703 red tree voles found in northern spotted owl (Strix occidentalis caurina) pellets collected in western Oregon during 1970–2009. The age distribution of red tree voles in pellets was dominated by young individuals, with 81% younger than one year and only 0.5% older than two years. The proportion of individuals 61–120 days old was particularly high relative to other age classes. The proportion of subadult (52–120 days old) individuals exhibited regional variation between the Oregon Cascades and the Coast Range. Localized annual variation in age distribution was low, exhibited no evidence of cyclic variation, and was positively associated with local precipitation rates during the spotted owl nesting season (March–June). We hypothesize that the age distribution of tree voles in owl pellets may be similar to the age structure of tree vole populations in the wild, but acknowledge that this is virtually impossible to test because tree voles cannot be adequately sampled using conventional small mammal capture methods.

Landscape connectivity and conservation prioritization for an old forest species with limited vagility

AbstractOld forests are often patchily distributed in contemporary forested landscapes leading to conservation concerns for species dependent on these forest types. In the absence of broad‐scale recovery of old forests, conservation initiatives have emphasized connecting forested landscapes to facilitate movement of genes or individuals. We assessed forest connectivity for a low‐vagile arboreal rodent (red tree vole; Arborimus longicaudus), an obligate of old forests within a distinct population segment that is a candidate for listing under the US Endangered Species Act in the northern Oregon Coast Range (USA). Within the distinct population segment, old forests (&gt;80 years old) have contracted by &gt;80% in the previous century, comprise 10.9% of the contemporary landscape and reside in a matrix of young forests (20–80 years old). We combined complimentary graph and circuit theory metrics into spatial conservation prioritization to provide insights into the composition and function of the contemporary forested landscape and to identify potential conservation and research priorities for this area. Given average distances from patches of old forests (3.4 km), we predicted that connectivity can only be achieved if red tree voles move and settle iteratively through young forest matrix, which is suboptimal habitat. We found that the top 1% conservation priorities were a series of small, spatially central patches and several large patches located where old forest cover was most extensive. Most of these patches were in protected reserves. Up to 30% of the top 10% prioritization were forests outside of reserves, highlighting the potential for these forests to contribute to landscape connectivity for this low‐vagile species that is dependent on old forest.

A tale of two voles: The challenge of the commonness-rarity continuum in conservation planning

Species rarity is often an important driver of conservation priorities in lieu of greater knowledge of extinction risk. Land management agencies often prioritize management based in part on the commonness of a species, yet identifying what constitutes where a species lies on the commonness-rarity continuum is difficult. Given limited resources, incorrect classification may have detrimental effects on species conservation. In a large area of the Northwest Forest Plan, which guides management of 9.1 million ha of federal forests in the Pacific Northwest, USA, forest management is closely tied to mitigation for the red tree vole (Arborimus longicaudus), a species considered uncommon due in part to its association with older forests. I explore the ability to provide insight into where a species lies along the commonness-rarity continuum by a multi-species comparison. I compared the relative distribution, abundance, and extrinsic conservation threats of red tree voles to western red-backed voles (Myodes californicus), a similar species considered common. Both species occur in younger forests with legacy components of older forests, but reach their greatest densities within older forests. Densities of the two vole species were qualitatively similar. If assignment of a species along a commonness-rarity continuum is a goal of species surveys, their value may be enhanced by including in the survey a set of similar species whose level of rarity is better understood. Although management of the red-tree vole was intended to be guided by adaptive management, challenging policy and legal issues have made that difficult; rarity as a criterion for prioritizing management is partly responsible.

Response of arboreal rodents to increased availability of nest substrates in young forests

Many forest-dependent animals require complex branch and bole structural features as substrates for nesting, and these features may take decades or centuries to develop. In young forests, lack of suitable nest substrates may limit occurrence and abundance of arboreal rodents. To test this hypothesis, we measured the response of arboreal rodents to installation of 429 artificial nest platforms at 17 young forest sites in the Coast Range of Oregon, United States. We compared the percentage of 100-m2 plots at sites containing nests before and after installation of nest platforms, and examined 5 a priori hypotheses of spatial patterns of use using logistic regression. One year after installation, we observed a 5.8-fold increase (95% CI = 2.4–9.2) in plots containing nests of red tree voles (Arborimus longicaudus) and a 2.9-fold increase (95% CI = 1.3–4.4) of tree squirrels (Glaucomys oregonensis, Tamiasciurius douglasii). In addition, we captured 37 adult red tree voles (30 females, 7 males). Presence of conspecific nests < 75 m away increased the odds of use by red tree voles but not by tree squirrels. Our results support the hypothesis that lack of suitable nest substrates limits occurrence of red tree voles in young forests, but results were ambiguous for tree squirrels. Increasing the availability of nest substrates via installation of nest platforms may increase abundance of red tree voles in young forests. However, we do not know if this will allow red tree voles to persist in young forests that are subjected to repeated commercial thinning and clear-cut harvesting.

Cytochrome P450 2B diversity in a dietary specialist—the red tree vole (Arborimus longicaudus)

AbstractAlthough herbivores rely on liver enzymes to biotransform plant secondary metabolites ingested in plant-based diets, only a few enzymes from a handful of species have been characterized at the genomic level. In this study, we examined cytochrome P450 2B (CYP2B) sequence diversity and gene copy number in a conifer specialist, the red tree vole (Arborimus longicaudus). We fed captive individuals exclusively Douglas-fir (Pseudotsuga menziesii) foliage, cloned and sequenced their liver CYP2B cDNA, and estimated CYP2B gene copy number. We identified 21 unique CYP2B nucleotide sequences, and 20 unique CYP2B amino acid sequences. Gene copy number of CYP2B was estimated at 7.7 copies per haploid genome. We compared red tree vole CYP2B with CYP2B sequences of a generalist, the prairie vole (Microtus ochrogaster), found in GenBank. Our study revealed that the CYP2B enzymes of red tree voles possess unique sequences compared to CYP2B enzymes of other herbivorous species. The unique combination of amino acid residues at key substrate recognition sites of CYP2B enzymes may underlie the ability of the red tree vole to specialize on a highly toxic diet of Douglas-fir.

Conservation and relative habitat suitability for an arboreal mammal associated with old forest

Contraction of native old forest can limit occurrence of old forest associated species, especially species with limited vagility. Patterns of size and distribution of remaining patches of old forest along with forest disturbance and what replaces old forest can influence whether species adapt or perish after forest loss. The arboreal red tree vole (Arborimus longicaudus) is a small arvicoline rodent that is associated with old coniferous forest and typically emigrates short distances. Since 1911, old forest (≥80years old) in the northern half of the Oregon Coast Range has been reduced by >80%, primarily due to large stand replacing wildfires, timber harvest, and subsequent conversion to young forest (<80years old). In 2011, the tree vole population in the northern half of the Oregon Coast Range was listed as a candidate species as a distinct population segment under the United States Endangered Species Act, primarily due to habitat loss. We examined the contribution of current and historical (early 20th century) old forest cover, and recent disturbances (1984–2012) on relative habitat suitability for tree voles using light detecting and ranging (LiDAR) data, Landsat imagery, and machine learning. We used a step-wise variable removal procedure to build a parsimonious model and to rank contribution of variables in our final model. We further described the configuration of large patches of old forest using metrics of amount and distance from patch for historical, current, two forest loss scenarios, and two forest restoration scenarios within our study area. Red tree vole relative habitat suitability was positively correlated with current old forest cover at the local-scale and negatively correlated with distance from large patches of current old forest. Landscape context, specifically proximity to old forest and absence of recent disturbance contributed most to relative habitat suitability of young forest matrix. If old forest contracted to only reserves on federal lands, amount would decrease from 10.9% to 9.5% and be spatially clumped with an increase in average distance to nearest patch from 3.1km to 11.1km. Alternatively, a random addition of patches equivalent to a 1.4% increase in amount, would reduce distance to nearest patch to 1.8km. Given the history of large historical wildfires in the Oregon Coast Range, restoration of even a small amount of old forest throughout the study area would likely enhance connectivity and resiliency of red tree vole populations in the event of large-scale loss of old forest.

Patterns of red tree vole distribution and habitat suitability: implications for surveys and conservation planning

AbstractEnvironmental regulations often require wildlife surveys prior to habitat disturbance to avoid impacts or as the basis for planning mitigation, yet project‐level surveys may not provide the insights needed to guide long‐term management. Management of the red tree vole (Arborimus longicaudus) has largely been based on such surveys. As an alternative approach, we evaluated distribution patterns using frequency of red tree vole occurrence and habitat suitability models to guide conservation planning. We developed a suite of models based on subsets of covariates from two previously developed models and evaluated the extent to which spatial covariates improved the models. We used presence–absence data that were collected from 364 randomly selected 1‐ha Current Vegetation Survey and Forest Inventory and Analysis plots to develop models and describe occurrence patterns. The best models included a spatial covariate, maximum tree diameter, distance from suitable habitat, forest age class, and the interaction between maximum tree diameter and forest age class. We compared performance of the previously published models, our best model, and an ensemble model that used predictions from all three models. Under the ensemble model, correct classification rates were relatively high and considerably improved, suggesting that the application of all three models provided greater accuracy than any individual model. We argue that habitat models, coupled with spatial patterns of the frequency of occurrence, can provide useful tools for addressing species management and may provide more insight than project‐level surveys. The use of habitat suitability models can therefore be closely tied to red tree vole management decisions and conservation strategies, as well as reducing survey costs that otherwise often make projects infeasible.

High‐resolution habitat modeling with airborne LiDAR for red tree voles

ABSTRACTHabitat suitability maps are important tools for conservation planning and species investigations, but maps at resolutions that are biologically meaningful and useful for local‐level decision‐making are lacking for many species that use resources at fine scales. Airborne light detection and ranging (LiDAR) describes 3‐dimensional structure of forests and other habitats at high resolution, which can improve habitat models for many species and facilitate investigations otherwise impossible with field data or other remote‐sensing techniques. We used an information‐theoretic approach and logistic regression to model habitat of red tree voles (Arborimus longicaudus) at multiple spatial scales with predictors derived from airborne LiDAR in southwestern Oregon. We developed a priori models to evaluate habitat associations and identify good models useful for high‐resolution mapping of habitat suitability across a large spatial extent. Our best models that compared habitats around nest trees of red tree voles to available sites performed well (i.e., accuracy = 0.83) on an independent test data set. We found fair performance in comparisons of habitat around nest trees to unused locations within areas previously identified as red tree vole habitat (i.e., accuracy = 0.71). Red tree vole nests were often in the largest trees in the stand and away from forest edges. Both analyses suggested that fine‐ and broad‐scale predictors are important for modeling habitat of red tree voles. Habitat suitability for red tree voles should be predicted effectively by LiDAR acquisitions even with low point densities because maps were robust to reductions in point densities as low as 1 point/m2. We found that LiDAR was effective for modeling habitat of red tree voles and expect it to improve performance of models for other species with similar habitat requirements. © 2016 The Wildlife Society.

Evaluating carbon storage, timber harvest, and habitat possibilities for a Western Cascades (USA) forest landscape.

Forest policymakers and managers have long sought ways to evaluate the capability of forest landscapes to jointly produce timber, habitat, and other ecosystem services in response to forest management. Currently, carbon is of particular interest as policies for increasing carbon storage on federal lands are being proposed. However, a challenge in joint production analysis of forest management is adequately representing ecological conditions and processes that influence joint production relationships. We used simulation models of vegetation structure, forest sector carbon, and potential wildlife habitat to characterize landscape-level joint production possibilities for carbon storage, timber harvest, and habitat for seven wildlife species across a range of forest management regimes. We sought to (1) characterize the general relationships of production possibilities for combinations of carbon storage, timber, and habitat, and (2) identify management variables that most influence joint production relationships. Our 160 000-ha study landscape featured environmental conditions typical of forests in the Western Cascade Mountains of Oregon (USA). Our results indicate that managing forests for carbon storage involves trade-offs among timber harvest and habitat for focal wildlife species, depending on the disturbance interval and utilization intensity followed. Joint production possibilities for wildlife species varied in shape, ranging from competitive to complementary to compound, reflecting niche breadth and habitat component needs of species examined. Managing Pacific Northwest forests to store forest sector carbon can be roughly complementary with habitat for Northern Spotted Owl, Olive-sided Flycatcher, and red tree vole. However, managing forests to increase carbon storage potentially can be competitive with timber production and habitat for Pacific marten, Pileated Woodpecker, and Western Bluebird, depending on the disturbance interval and harvest intensity chosen. Our analysis suggests that joint production possibilities under forest management regimes currently typical on industrial forest lands (e.g., 40- to 80-yr rotations with some tree retention for wildlife) represent but a small fraction of joint production outcomes possible in the region. Although the theoretical boundaries of the production possibilities sets we developed are probably unachievable in the current management environment, they arguably define the long-term potential of managing forests to produce multiple ecosystem services within and across multiple forest ownerships.

Distribution and Abundance of Tree Voles in the Northern Coast Ranges of Oregon

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 (≥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).

Water Consumption by Red Tree Voles (Arborimus longicaudus)

We studied consumption of free water by a sample of 7 Red Tree Voles (Arborimus longicaudus) maintained in captivity on a natural diet of Douglas-fir (Pseudotsuga menziesii) foliage. Mean consumption of free water by individual voles was 0.016 ± 0.001 ml/g/d, which is much lower than has been reported for most other species of voles. The small amount of free water consumed per day suggests that Tree Voles need little access to free water and can obtain nearly all of their water from their diet of conifer needles, which is low in caloric value but high in water content.

Hierarchical Bayesian Spatial Models for Multispecies Conservation Planning and Monitoring

Biologists who develop and apply habitat models are often familiar with the statistical challenges posed by their data's spatial structure but are unsure of whether the use of complex spatial models will increase the utility of model results in planning. We compared the relative performance of nonspatial and hierarchical Bayesian spatial models for three vertebrate and invertebrate taxa of conservation concern (Church's sideband snails [Monadenia churchi], red tree voles [Arborimus longicaudus], and Pacific fishers [Martes pennanti pacifica]) that provide examples of a range of distributional extents and dispersal abilities. We used presence-absence data derived from regional monitoring programs to develop models with both landscape and site-level environmental covariates. We used Markov chain Monte Carlo algorithms and a conditional autoregressive or intrinsic conditional autoregressive model framework to fit spatial models. The fit of Bayesian spatial models was between 35 and 55% better than the fit of nonspatial analogue models. Bayesian spatial models outperformed analogous models developed with maximum entropy (Maxent) methods. Although the best spatial and nonspatial models included similar environmental variables, spatial models provided estimates of residual spatial effects that suggested how ecological processes might structure distribution patterns. Spatial models built from presence-absence data improved fit most for localized endemic species with ranges constrained by poorly known biogeographic factors and for widely distributed species suspected to be strongly affected by unmeasured environmental variables or population processes. By treating spatial effects as a variable of interest rather than a nuisance, hierarchical Bayesian spatial models, especially when they are based on a common broad-scale spatial lattice (here the national Forest Inventory and Analysis grid of 24 km(2) hexagons), can increase the relevance of habitat models to multispecies conservation planning.

Identifying Shared Genetic Structure Patterns among Pacific Northwest Forest Taxa: Insights from Use of Visualization Tools and Computer Simulations

BackgroundIdentifying causal relationships in phylogeographic and landscape genetic investigations is notoriously difficult, but can be facilitated by use of multispecies comparisons.Methodology/Principal FindingsWe used data visualizations to identify common spatial patterns within single lineages of four taxa inhabiting Pacific Northwest forests (northern spotted owl: Strix occidentalis caurina; red tree vole: Arborimus longicaudus; southern torrent salamander: Rhyacotriton variegatus; and western white pine: Pinus monticola). Visualizations suggested that, despite occupying the same geographical region and habitats, species responded differently to prevailing historical processes. S. o. caurina and P. monticola demonstrated directional patterns of spatial genetic structure where genetic distances and diversity were greater in southern versus northern locales. A. longicaudus and R. variegatus displayed opposite patterns where genetic distances were greater in northern versus southern regions. Statistical analyses of directional patterns subsequently confirmed observations from visualizations. Based upon regional climatological history, we hypothesized that observed latitudinal patterns may have been produced by range expansions. Subsequent computer simulations confirmed that directional patterns can be produced by expansion events.Conclusions/SignificanceWe discuss phylogeographic hypotheses regarding historical processes that may have produced observed patterns. Inferential methods used here may become increasingly powerful as detailed simulations of organisms and historical scenarios become plausible. We further suggest that inter-specific comparisons of historical patterns take place prior to drawing conclusions regarding effects of current anthropogenic change within landscapes.

Survival, Mortality, and Predators of Red Tree Voles (Arborimus longicaudus)

Abstract Although estimations of vital rates are important to understand population dynamics of small mammals, there is little information on survival rates and causes of mortality for many species. In 2002–2003, we estimated monthly and annual survival of 50 radiocollared red tree voles (Arborimus longicaudus) during a study of movements and diel activity patterns in western Oregon. Estimated annual survival for both sexes combined was 0.15 (95% CI = 0.06 to 0.31) and was influenced little by mass at initial capture. In the analysis of explanatory variables, we did not find strong effects of gender, vole age, or forest age on survival. We suspect this may have been due to small sample size and low power to detect effects, because some of the point estimates were suggestive of large differences among groups. Most mortality was due to predation, with 15 of 25 deaths attributed to weasels (Mustela spp.). Weasels preyed upon significantly more females than males (14:1, respectively). Other confirmed or suspe...

Doug Bake and Red Tree Voles: A Tale of Discovery in the Pacific Northwest

In 2002, we began compiling a database on all historical locations of Red Tree Voles (Arborimus longicaudus) and Sonoma Tree Voles (A. pomo) in Oregon and California. Part of that exercise involved visiting museums that had Tree Vole specimens and reading the old field notes of previous researchers who had collected museum specimens. As we began reading field notes and looking at specimens, we noticed that a remarkable number of Red Tree Voles had been collected around Tillamook, OR, in the 1960s and 1970s by a logger named Doug Bake. Most of the Red Tree Voles that Doug collected were prepared by Murray Johnson, then curator of mammals at the Slater Museum of Natural History at the University of Puget Sound in Tacoma, WA. Prior to preparing them as study skins, Murray kept many of Doug’s voles in captivity to study their behavior. He even used them in experimental crosses with Sonoma Tree Voles that he collected in California and found that these matings were not very successful, suggesting a reproductive barrier between Red and Sonoma Tree Voles (Johnson and George 1991). Murray also used some of Doug’s voles in feeding trials to see if individuals that normally fed on needles of Western Hemlock (Tsuga heterophylla) could switch to Douglas-fir (Pseudotsuga menziesii); he discovered that they did poorly at this. Though Murray had passed away by the time we started compiling our database, we were curious about whether Doug Bake was still alive, and, if so, we hoped to talk to him about how he came to be interested in Red Tree Voles and how he was able to capture so many of them. So we checked the Tillamook phone directory and found him listed. Because we knew that he had to be quite old, we were reluctant to simply call him up, so we decided to write him instead. About a week after we sent him a letter, we got a response back from Doug, written in his distinctive block print, saying that ‘‘It’s been over 20 years since I fell timber and my memory is a little rusty. However, if I can recollect anything beneficial, I’d be glad to talk with you.’’ We were elated by Doug’s quick response, so we immediately called him up and arranged to meet with him at his home on the outskirts of Tillamook. We met on 1 August 2003 and spent a couple of hours sitting on Doug’s couch, talking to him about his days in the woods and his interactions with Murray Johnson and Alex Walker, another Tillamook resident and one of the earliest naturalists to study mammals in northwest Oregon (Walker 1928, 1930). After our visit, we were so impressed with Doug and his unique contribution to science that we were inspired to write the following article. It is part obituary, but more than that, it is an example of what an ordinary lay person can contribute to science if they really desire to.