Beavers have become a source of inspiration for public and private land managers over the past decade. Beaver dams can help control flooding, raise groundwater levels, and improve surface water flows. Some land managers are now designing stream restoration projects that mimic the way beaver dams shape river ecosystems. Beaver-related restoration may even help the recovery of endangered species that depend on healthy aquatic and riparian areas.
The approach also holds promise for ranchers who graze livestock on rangelands in the Western United States where drier conditions are expected in the coming years. Those already experimenting with beaver-related restoration are discovering that it can increase water and forage availability for their livestock.
Until recently, the social factors that influence the success or failure of these projects on rangelands were not well understood. To assess the social and regulatory environment associated with this new approach, Susan Charnley, a research social scientist with the USDA Forest Service, Pacific Northwest Research Station, and her colleagues conducted five case studies in California, Idaho, Nevada, and Oregon. Interviews with more than 100 ranchers, nongovernmental organizations, and regulatory agencies shed light on their attitudes and motivations, as well as the regulatory landscape that influences successful implementation. The findings are important for successfully implementing beaver-related restoration projects in other areas.
Pacific martens (Martes caurina) remain common in montane regions of the Pacific states, yet their distribution and status on the Olympic Peninsula, Washington, is uncertain. Between 1968–2008, six reliable marten detections exist; a dead juvenile female (2008) indicates martens were reproducing on the Peninsula within the last decade. To assess the status of martens, we describe carnivore surveys conducted from 1991–2008 (n = 223 stations). Additionally, we present results from three survey efforts we conducted from 2013–2016 (n = 747 stations). Although a suite of carnivore species was detected, surveys from 1991–2008 failed to detect either martens or fishers. Surveys from 2013–2016 detected reintroduced fishers, and resulted in two marten detections near Mt. Olympus, 4 km apart. A marten was photographed opportunistically near Mt. Cruiser in 2015, 44 km from Mt. Olympus. Altogether, nine reliable detections of Pacific martens were obtained between 1968 and 2016, including three since 2008. Evidence suggests martens are absent from the lower elevation regions they once occupied and occur at exceedingly low densities at higher elevations. To understand the trend in marten populations on the Peninsula and develop appropriate conservation strategies, additional broad- and fine-scale surveys using detection devices that enable the genetic identification of individuals will be needed.
Live trapping is a common tool used to assess demography of small mammals. However, live-trapping is often expensive and stressful to captured individuals. Thus, assessing the relative tradeoffs among study goals, project expenses, and animal well-being is necessary. Here, we evaluated how apparent bias and precision of estimates for apparent annual survival, abundance, capture probability, and recapture probability of Humboldt’s flying squirrels (Glaucomys oregonensis) varied with the number of secondary trapping occasions. We used data from forested sites trapped on 12 consecutive occasions annually in the HJ Andrews Experimental Forest (9 sites, 6 years) and the Siuslaw National Forest (seven sites, three years) in Oregon. We used Huggins robust design models to estimate parameters of interest for the first 4, 8, and 12 trapping occasions. We also estimated the effect of attaching Tomahawk traps to tree boles on site- and year-specific flying squirrel capture frequencies. Our estimates with 12 occasions were similar to those from previous studies. Abundances and capture probabilities were variable among years on both sites; however, variation was much lower on the Siuslaw sites. Reducing the length of primary trapping occasions from 12 to 8 nights had very little impact on parameter estimates, but further reducing the length of primary trapping occasions to four nights caused substantial apparent bias in parameter estimates and decreased precision. We found that attaching Tomahawk traps to tree boles increased the site- and year-specific capture frequency of flying squirrels. Our results suggest that live-trapping studies targeting Humboldt’s flying squirrels in the Pacific Northwest of the United States could reduce per-site costs and stress to captured individuals without biasing estimates by reducing the length of primary trapping occasions to 8 nights. We encourage similar analyses for other commonly-trapped species in these and other ecosystems.
Old 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 (>80 years old) have contracted by >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.
Recurrent environmental changes often prompt animals to alter their behavior leading to predictable patterns across a range of temporal scales. The nested nature of circadian and seasonal behavior complicates tests for effects of rarer disturbance events like fire. Fire can dramatically alter plant community structure, with important knock‐on effects at higher trophic levels, but the strength and timing of fire's effects on herbivores remain unclear. We combined prescribed fire treatments with fine‐scale location data to quantify herbivore responses to fire across three temporal scales. Between 2001 and 2003, 26 stands of fir (Abies spp.) and Douglas‐fir (Pseudotsuga menziesii) were thinned and burned; 27 similar stands were left untreated as experimental controls. Analyzing female elk (Cervus canadensis) locations across 21 yr (1996—2016), we found crepuscular, seasonal, and successional shifts in behavioral responses to fire. Elk displayed “commuting” behavior, avoiding burns during the day, but selecting them at night. Elk selection for burns was strongest in early summer and the relative probability of elk using burns peaked quickly (5 yr post burn) before gradually returning to pre‐treatment levels (15 yr post burn). Our results demonstrate that fire history has complex, persistent effects on herbivore behavior, and suggest that herbivores benefit from heterogeneous landscapes containing a range of successional stages.
In this article we respond to a recent paper in which Rosenberg (2019) suggested that red tree voles (Arborimus longicaudus) were just as common as western redbacked voles (Myodes californicus) and implied that federal management agencies should consider dispensing with field surveys of red tree voles in favor of an unspecified adaptive management approach. Our primary purpose in writing this response is not to debate how management agencies should manage red tree voles. Our objective is to demonstrate that Rosenberg’s (2019) attempt to compare the distribution and relative abundance of red tree voles and western red-backed voles was fundamentally flawed. The data that he used to compare the two species are not analogous because they are based on different metrics, biased samples, and different sampling techniques. Rosenberg (2019) also failed to include data from numerous studies that suggest that, compared to red tree voles, western red-backed voles are much more uniformly distributed in the coniferous forests of western Oregon. In addition to assessing the methodological flaws and inconsistencies in Rosenberg’s (2019) analysis, we review additional data that we think are useful for understanding differences in the distribution of tree voles and red-backed voles. We conclude that Rosenberg’s (2019) analysis served little purpose except to muddy the waters regarding the actual distribution and abundance of red tree voles.
Effective conservation and management of small mammals require knowledge of the population dynamics of co-occurring species. We estimated the abundances, autocorrelations, and spatiotemporal associations of 4 small-mammal species from 2011–2016 using live-trapping mark-recapture methods on 9 sites across elevation and canopy openness gradients of a late-successional forest in the H. J. Andrews Experimental Forest, on the west slope of the Oregon Cascades. We also quantified species-specific spatial variation in adult sex ratios and body mass. We used Huggins closed capture models to estimate site and year-specific abundances of 4 target species: Humboldt’s flying squirrels (Glaucomys oregonensis), Townsend’s chipmunks (Neotamias townsendii), western red-backed voles (Myodes californicus), and deer mice (Peromyscus maniculatus). We estimated the temporal autocorrelations among site- and species-specific abundance estimates and used generalized linear mixed effects models to investigate the effects of 7 spatiotemporal covariates on species-specific mean abundance estimates. Species-specific adult sex ratios, juvenile to adult ratios, and adult body masses were not widely variable among study sites. Abundance estimates varied by as much as 4-fold among years and 6-fold among sites. Humboldt’s flying squirrel abundance was temporally autocorrelated at intervals of 1 and 5 years, Townsend’s chipmunk abundance was temporally autocorrelated at intervals of 1–4 years, and western red-backed vole abundance was temporally autocorrelated at 1, 4, and 5 years. Mean fall abundance estimates were associated with elevation and climate and in some cases, canopy openness and berry-producing shrubs, but the direction of the association differed among species for some covariates. Our findings could provide additional management tools for small-mammal abundance objectives, and highlight the importance of careful covariate selection in studies using indices of small-mammal abundance.
Recently, Stewart et al. (2017) investigated the origins of contemporary fisher populations in the Cooking Lake Moraine (CLM) of east-central Alberta, Canada, where fishers (Pekania pennanti) from Ontario and Manitoba, Canada were reintroduced in the early 1990s. To address this objective, Stewart et al. (2017) compared microsatellite alleles from extant fisher populations in the CLM to those from Ontario, Manitoba, and other Alberta populations. They reported that the CLM population clustered with adjacent native Alberta populations, consistent with recolonization, but also that 2 of 109 microsatellite alleles in the CLM occurred only in the source populations from Ontario and Manitoba. Rather than allowing for the possibility that these alleles descended from reintroduced fishers, the authors speculated that they represented random mutations among fishers that recolonized the area naturally from nearby populations in Alberta, and concluded that the reintroduction had failed completely. We disagree with this conclusion for 2 reasons. We contend it is more likely that the 2 alleles represent a genetic signature from the individuals released during the reintroduction, rather than being the result of mutations. We further suggest that, irrespective of the genetic legacy of introduced fishers in the recovered population, the presence of reintroduced fishers in the CLM may have helped facilitate natural recolonization of the area by fishers from surrounding areas. In our view, Stewart et al.’s (2017) findings do not demonstrate conclusively that the reintroduction program failed; on the contrary, we argue that their findings indicate that reintroduced fishers likely contributed to the long-term persistence of fishers in the CLM. The uncertainty surrounding this case underscores the importance of genetic monitoring following reintroductions.