Pekania Pennanti Research Articles

Abiotic conditions mediate intraguild interactions between mammalian carnivores.

Intraguild (IG) interactions are common among mammalian carnivores, can include intraguild predation (IGP) and interspecific killing (IK), and are often asymmetrical, where a larger more dominant species (IGpredator ) kills a smaller one (IGprey ). According to ecological theory, the potential for an IGpredator and IGprey to coexist depends on whether the direct consumptive benefits for the IGpredator are substantial (IGP) or insignificant (IK), the extent to which the IGprey is the superior exploitative competitor on shared prey resources, and overall ecosystem productivity. We used resource selection models and spatially explicit age and harvest data for two closely related mesopredators that engage in IG interactions, American martens (Martes americana; IGprey ) and fishers (Pekania pennanti; IGpredator ), to identify drivers of distributions, delineate areas of sympatry and allopatry, and explore the role of an apex predator (coyote; Canis latrans) on these interactions. Model selection revealed that fisher use of this landscape was strongly influenced by late winter abiotic conditions, but other bottom-up (forest composition) and top-down (coyote abundance) factors also influenced their distribution. Overall, fisher probability of use was higher where late winter temperatures were warmer, snowpack was deeper, and measures of productivity were greater. Martens were constrained to areas of the landscape where the probability of fisher use, coyote abundance, and productivity were low and selected for forest conditions that presumably maximized prey availability. Marten age data indicated an increased proportion of juveniles outside of the predicted area of sympatry, suggesting that few animals survived >1.5years in this area that supported higher densities of fishers and coyotes. Consistent with asymmetrical IG interaction theory, the IGpredator (fishers and, to a lesser degree, coyotes) competitively excluded the IGprey (martens) from more productive, milder temperature habitats, whereas IGpredators and IGprey coexisted in low productivity environments, where a combination of abiotic and biotic conditions enabled the IGprey to be the superior exploitative competitor.

Assessing arrays of multiple trail cameras to detect North American mammals.

Motion triggered camera traps are an increasingly popular tool for wildlife research and can be used to survey for multiple species simultaneously. As with all survey techniques, it is crucial to conduct camera trapping research following study designs that include adequate spatial and temporal replication, and sufficient probability of detecting species presence. The use and configuration of multiple camera traps within a single survey site are understudied considerations that could have a substantial impact on detection probability. Our objective was to test the role that camera number (one, two or three units), and spacing along a linear transect (100 m or 150 m), have on the probability of detecting a species given it is present. From January to March, 2017 we collected data on six mammal species in Maine, USA: coyote (Canis latrans), fisher (Pekania pennanti), American marten (Martes americana), short-tailed weasel (Mustela erminea), snowshoe hare (Lepus americanus), and American red squirrel (Tamiasciurus hudsonicus). We used multi-scale occupancy modelling to compare pooled detection histories of different configuration of five cameras deployed at the same survey site (n = 32), and how the configuration would influence the probability of detecting a species given it was available at the site. Across all six species, we found substantial increases in probability of detection as the number of cameras increased from one to two (22 to 400 percent increase), regardless of the spacing between cameras. For most species the magnitude of the increase was less substantial when adding a third camera (4 to 85 percent increase), with coyote and snowshoe hare showing a pronounced effect. The influence of survey station features also varied by species. We suggest that using pooled data from two or three cameras at a survey site is a cost effective approach to increase detection success over a single camera.

Reproductive den selection and its consequences for fisher neonates, a cavity-obligate mustelid

AbstractSelection of habitat characteristics by reproductive females during neonate development can mediate the influence of adverse environmental conditions on the fitness of offspring. Previous research has suggested that cavities and burrows used for reproduction by cavity-obligate species offer thermoregulatory benefits, access to prey, and can limit predation pressure. As fishers (Pekania pennanti) are secondary cavity-obligate breeders, we hypothesized that they select particular characteristics of reproductive den cavities at discrete stages of offspring development to mediate adverse biotic and environmental effects on their neonates. To test our hypothesis, we located 406 reproductive dens and 154 cavity rest sites used by 65 individual adult female fishers during 11 reproductive seasons (2005–2016) in northwestern California. We counted 53 (27 F, 26 M) kits in 31 litters born to 19 females during six of these reproductive seasons. The weight of kits varied significantly by sex and by age, whereas the length of kits varied only by age, suggesting that adult females in this population might be preferentially investing in male kits. We found that natal and early-maternal dens buffered minimum temperatures significantly more than late-maternal dens and cavities used during the nonreproductive season. A male fisher skull was also less likely to fit through the cavity openings of natal dens than through the openings of cavities used by adult females during the nonreproductive season. Litter survival was significantly lower at natal dens than at late-maternal dens. The age of adult female fishers did not affect the probability of litter survival. Our results emphasize the vulnerability of vertebrate offspring during early developmental periods and how cavity-obligate species select cavities to mediate environmental conditions during reproduction.

The Effect of Time and Forest Disturbances on the Structural and Functional Characteristics of Fisher (Pekania pennanti) Resting Structures

The fisher is a mammalian carnivore that chooses resting locations each day. Refugia are essential, thus most of the fisher's resting locations are cavities in large live or dead trees. Tree growth and decomposition influence the creation of cavity-bearing structures, which may take centuries, but they can be lost to fire or harvest in an instant. Thus, the conservation of the fisher relies on an equilibrium between the loss of structures via disturbance and their creation. In the mid-1990s we studied fisher resting habitat by following radio-marked individuals to their resting locations. In 2016, roughly 20 years later, we assessed the risks that the resting structures were exposed to by overlaying the perimeters of fires and tree harvest units on the location of 192 resting structures. We also assess the effect of disturbance by examining 36 of them in the field. The mean distance from a resting structure to the nearest harvest unit was 651 m, with 16.8% estimated to be within a harvest unit. The mean distance of the resting structures to the nearest fire was 635 m with 51.0% estimated to be within a fire. Of 36 resting structures that were reevaluated or relocated in the field, 16 (44.4%) were of questionable use in 2016. Based on GIS analyses of disturbance coupled with field data on relocated structures, approximately 15–25% were potentially usable after 20 years. Managers planning actions should consider this a background level of loss of resting structures over 20 years—a background against which additional vegetation management can be considered.

Habitat selection and spatiotemporal interactions of a reintroduced mesocarnivore

ABSTRACTHabitat quality and quantity are key factors in evaluating the potential for success of a wildlife translocation. However, because of the difficulty or cost of evaluating these factors, habitat assessments may not include valuable information on important habitat attributes including the abundance and distribution of prey, predators, and competitors. Fishers (Pekania pennanti) are one of the most commonly reintroduced carnivores in North America, and they are a species of conservation concern in their western range. We examined the relative importance of landscape features and species interactions in determining habitat use of a reintroduced population of fishers in the southern Cascade Mountains, Washington, USA. We used detections of prey and predators at 134 remote camera stations, remotely sensed forest structure data, and telemetry locations of fishers in a resource selection function to assess the relative importance of prey, predators, and forest structure in fisher habitat selection. Fishers selected habitats based on forest conditions and activity levels of snowshoe hares (Lepus americanus), whereas bobcat (Lynx rufus) and coyote (Canis latrans) activity levels did not directly affect habitat selection. The probability of fisher use increased in older stands, close to recently disturbed stands, and in areas with intermediate levels of hare activity. Bobcat and hare activity levels were positively correlated, and fishers avoided areas with the greatest hare activity, suggesting that fishers may experience a food‐safety tradeoff in the study area. Temporal activity patterns in photo detections indicate that fishers may mediate this danger by avoiding bobcats temporally. Our findings suggest that fishers in Washington prefer habitat mosaics of old and recently disturbed stands where they have greater access to resting structures and hares. Management that maintains mosaics of young and old forest across large landscapes is likely to support fisher recovery. Future reintroduction efforts would benefit from an assessment of prey and predator abundance in proposed reintroduction areas before project initiation. © 2019 The Wildlife Society.

The Debate About Bait: A Red Herring in Wildlife Research

ABSTRACTThe use of bait (or attractants) to lure animals to a sampling site is common in wildlife research and important for optimizing species detection rates. The effect of bait on animal movement and space‐use, however, is contested, fueled by concerns bait may affect animal movement and increase residency time. If founded, bait may bias parameter estimates from density, species distribution, resource selection, or behavioral models, produce spurious ecological inferences, and skew resulting management recommendations. To test whether animal movement varies with proximity to bait, we used high‐resolution global positioning system telemetry data of 10 fishers (Pekania pennanti), temporally paired with 64 baited wildlife camera traps, to quantify the effect of bait on individual and population movement metrics. Although bait appeared to have a significant correlative effect on 1‐hour movement segments, landscape characteristics had an effect 1.7 times greater, where the proportion of mixed forest and cultivation explained the majority of variability in animal movements. We contend that maximizing probability of detection and controlling or modeling local‐scale landscape variability that could affect the probability of detection is a more important consideration in wildlife research than the effect of bait, which is eclipsed by differences incurred by natural habitat heterogeneity. Failing to maximize the probability of detection may obscure the modest bias potentially presented by the use of bait, or attractants, on ecological inference. © 2019 The Wildlife Society

Forest structure predictive of fisher (Pekania pennanti) dens exists in recently burned forest in Yosemite, California, USA

One challenge that land managers face in the southern Sierra Nevada is how to balance conservation of fisher (Pekania pennanti) habitat with the reintroduction of fire. The fisher population in the southern Sierra Nevada is of high conservation priority, due to its small population size, genetic isolation, and the risk of habitat loss due to wildfire and fuel reduction activities. It is unknown whether contemporary forests altered by fire suppression can support fisher habitat following the reintroduction of fire. We examined whether patch-scale forest habitat conditions used by fishers in a landscape with limited recent fire (Dinkey study area) also exist in a landscape with restored fire (Yosemite study area). We developed random forest and logistic regression models using lidar-derived forest structure metrics to distinguish reproductive den presence (n = 261) from randomly-generated “available” points (n = 261) within an estimate of the female population home range. The full logistic regression model correctly classified (under cross-validation) 69.5% of observations and the random forest model correctly classified 74.3%. The parsimonious logistic regression model we selected had comparable accuracy to the full model (correctly classified 68.8% of observations) and included the following variables: cover >2 m, 95th percentile height, and 25th percentile height. Partial dependence plots suggest thresholds at which predicted probability of reproductive den presence exceeds 50%: cover >2 m greater than 60%, 95th percentile height of at least 32 m, and 25th percentile height between 4 m and 14 m. We found that comparable thresholds of forest cover and tree height exist in burned areas in Yosemite; 43.0% of burned pixels had similar lidar-derived forest structural characteristics to those predictive of reproductive dens in Dinkey. Areas with similar forest structures occurred within a range of fire severities and years since the most recent fire, and particularly in low-severity fire conditions (mean differenced normalized burn ratio [dNBR] value: 128.4). These results are promising for land managers who face the challenge of simultaneously reducing the risk of high-severity fire and conserving fisher habitat, however more research is needed to conclude whether suitable fisher habitat can exist in burned areas at all scales of selection and for all activities of the fisher population.

Microsites and structures used by fishers (Pekania pennanti) in the southern Sierra Nevada: A comparison of forest elements used for daily resting relative to reproduction

Many wildlife species rely on unique features of trees during daily activities and fundamental parts of their life cycle. The fisher (Pekania pennanti) is a forest-dwelling carnivore of conservation concern in western North America that uses unique habitat elements as refuges during resting bouts and for reproduction. Prior to this study, little was known about the fine-scale habitat used during reproduction at the southernmost extent of the fisher’s range. Between 2007 and 2015, we attached radio-collars to 55 male and 72 female fishers in the southern Sierra Nevada and documented resting locations of males on 216 occasions (196 structures) and females on 824 occasions (737 structures). Beginning in 2008, we also monitored females over 8 reproductive seasons, confirming 45 females at dens and documenting 95 natal dens (83 structures) and 206 maternal dens (192 structures). We established 3 comparisons to guide our assessment of fine-scale habitat: resting males versus resting females, natal dens versus maternal dens, and resting fishers (both sexes) versus denning fishers (all dens). We expected the need for physical security and thermal protection in combination with morphology, predation risk, and aspects of reproductive ecology would influence patterns of use. Both sexes used a variety of microsites for resting, but females selected tree cavities most frequently (47%) while males used branch platforms most often (39%). For resting structures, live conifers were used most often by both sexes (males 44%, females 34%), but live hardwoods (males 16%, females 28%) and conifer snags (males 16%, females 22%) were also important. Comparing natal and maternal dens, we found that cavity microsites used early in the den season tended to be higher than those used later, and large live hardwoods comprised roughly half of all natal (46%) and maternal (51%) den structures. For resting versus denning, we found that large diameter hardwoods were an important source of cavities for both activities, live conifers used for denning were larger than those used for resting, and den structures tended to be on steeper slopes than rest structures. White fir (Abies concolor), California black oak (Quercus kelloggii), and ponderosa pine (Pinus ponderosa) were selected most often by both sexes for resting. In contrast, denning females relied on California black oak (55%), but also used white fir (24%) and incense cedar (Calocedrus decurrens; 12%). As noted in studies further north, our findings highlight the value of large trees with decay to support fisher reproduction and daily refugia.

Resource limitations and competitive interactions affect carnivore community composition at different ecological scales in a temperate island system

AbstractSelective pressures (i.e. resource limitation and competitive interaction) that drive the composition of ecological communities vary, and often operate on different ecological scales (ecological variables across varying spatial scales) than observed patterns. We studied the drivers of distribution and abundance of the American marten (Martes americana) and the carnivore community at three ecological scales on a Great Lakes island archipelago using camera traps. We found different drivers appeared important at each ecological scale and studying any of the three scales alone would give a biased understanding of the process driving the system. Island biogeography (resource limitation) was most important for carnivore richness, with higher richness on larger islands and lower richness as distance from the mainland increased. Marten presence on individual islands appeared to be driven by island size (resource limitation) and human avoidance (competitive interaction). Marten abundance at camera trap sites was driven by the cascading effect of coyotes (Canis latrans) on fishers (Pekania pennanti) (competitive interaction). Incorporating three ecological scales gave novel insights into the varying effects of resource limitation and competitive interaction processes. Our data suggests that ecological communities are structured through multiple competing ecological forces, and effective management and conservation relies on our ability to understand ecological forces operating at multiple ecological scales.

A carnivores’ oasis? An isolated fisher (Pekania pennanti) population provides insight on persistence of a metapopulation

Landscape level species assessments are rarely available to inform conservation planning. Recent advances in multi-taxa survey techniques, however, have made them more obtainable by improving efficiency of collecting species occurrence data and genetic samples. Here, we used a multi-taxa survey technique to provide a landscape level portrait of fisher (Pekania pennanti) population status in a portion of the northern Rockies where the species’ history has been heavily influenced by humans. From 2010 to 2014 we deployed 497 winter forest carnivore bait stations across a 23,000 km2 study area centered on northern Idaho, United States. The stations collected remote camera images and hair samples for DNA analysis. We used 12 microsatellite loci to identify 58 individual fisher in the study area. We identified two fisher populations for which we estimated effective population size (Ne) and genetic neighborhood size (NS). We calculated local genetic diversity measures [observed (Ho) and expected (He) heterozygosity, allelic richness (Ar), fixation index (FST), and number of migrants per generation (Nm)] and mapped continuous gradients of genetic diversity [Ar and inbreeding coefficient (FIS)] across the study area. We identified a fisher population in the West Cabinet Mountains [Ne of 26 (15.3–55.5), NS of 50–60] which is effectively isolated from the small population we detected in the Saint Joe/Coeur d’Alene Mountains [Ne of 6.5 (2.7–15), NS of 10–25]. We determined fisher have been effectively extirpated from the Selkirk and Purcell mountains and the lack of genetic connectivity between the two small remaining populations casts doubt on long term viability. Our study suggests northern Rockies fisher populations are vulnerable to landscape barriers and successful recovery will depend on future management and augmentation. We recommend these factors be considered when determining how, and if, species recovery should proceed.

A Leucisitic Fisher (Pekania pennanti) and the Prevalence of Leucism in Wild Carnivores

Animal coloration has adaptive roles for communication, concealment, sexual selection, and physiological function. Genetic mutations sometimes cause abnormal coloration such as leucism, in which an animal appears partially or entirely white, except for exposed soft skin tissue. Here we document a leucistic fisher (Pekania pennanti). Fisher fur normally ranges from deep brown to black, but the function of the pelt color is not understood. The literature on the occurrence of leucism includes 33 other records of leucism among carnivores. Reporting cases of rare coloration in the wild helps to understand the distribution, prevalence, and significance of abnormal colors.

Animal movement tools (amt): R package for managing tracking data and conducting habitat selection analyses.

Advances in tracking technology have led to an exponential increase in animal location data, greatly enhancing our ability to address interesting questions in movement ecology, but also presenting new challenges related to data management and analysis. Step‐selection functions (SSFs) are commonly used to link environmental covariates to animal location data collected at fine temporal resolution. SSFs are estimated by comparing observed steps connecting successive animal locations to random steps, using a likelihood equivalent of a Cox proportional hazards model. By using common statistical distributions to model step length and turn angle distributions, and including habitat‐ and movement‐related covariates (functions of distances between points, angular deviations), it is possible to make inference regarding habitat selection and movement processes or to control one process while investigating the other. The fitted model can also be used to estimate utilization distributions and mechanistic home ranges. Here, we present the R package amt (animal movement tools) that allows users to fit SSFs to data and to simulate space use of animals from fitted models. The amt package also provides tools for managing telemetry data. Using fisher (Pekania pennanti) data as a case study, we illustrate a four‐step approach to the analysis of animal movement data, consisting of data management, exploratory data analysis, fitting of models, and simulating from fitted models.

Activity of fishers at multiple temporal scales

Ecologically relevant multi-temporal-scale frameworks elucidate whether patterns of animal activity (movement) are distinct at different temporal scales. We studied fishers (Pekania pennanti) fitted with transmitter collars that measured activity at high temporal resolution during winter in Wisconsin. A multi-temporal-scale framework with two scales, day (number of activity bouts per 24 h) and decision (time spent exploring a small area), revealed that the best models of fisher activity were different at different temporal scales. At the day scale, the fishers that we studied increased activity when temperatures were warmer and increased activity more when it was windy and cold than when it was windy and warm. At the decision scale, when wind speeds increased, female fishers reduced activity more than male fishers. The role of temperature on activity was only detected at the day scale, and intersexual variation was only detected at the decision scale. Results at both scales supported the prey synchrony hypothesis for activity, but support was mixed at the day scale. Assessing activity using a multi-temporal-scale analysis framework leads to a better understanding of factors that influence activity and biological fitness.

Using environmental DNA methods to improve winter surveys for rare carnivores: DNA from snow and improved noninvasive techniques

The management of rare species is a conservation priority worldwide, but this task is made difficult by detection errors in population surveys. Both false positive (misidentification) and false negative (missed detection) errors are prevalent in surveys for rare species and can affect resulting inferences about their population status or distribution. Environmental DNA (eDNA)—DNA shed from an organism in its environment—coupled with quantitative PCR (qPCR) analyses, has become a reliable and extremely sensitive mean for identifying rare species in aquatic systems. Due to the demonstrated effectiveness of these methods, we tested their efficacy in surveys for rare species in terrestrial settings to reduce detection errors for three rare forest carnivores of conservation concern: Canada lynx (Lynx canadensis), fisher (Pekania pennanti), and wolverine (Gulo gulo). We specifically investigated our ability to reliably: 1) identify species directly from snow samples collected within tracks; 2) identify species by collecting snow in locations where an animal had been photographed; and 3) identify species from hair samples collected during the summer after being deployed throughout the winter (i.e., overwinter surveys). Our findings indicated that qPCR assays can effectively detect DNA of all three species, including from snow-track surveys, snow collected at camera stations, and overwinter samples that failed to amplify with conventional PCR techniques. All results indicate that the sources of targeted DNA collection provided adequate quantities of DNA for robust species detection. We suggest that using qPCR methods to detect DNA has the potential to revolutionize winter surveys for rare species in terrestrial settings by reducing or eliminating misidentifications and missed detections.

Establishing Bayesian priors for natural mortality rate in carnivore populations

ABSTRACTIn managed carnivore populations, natural mortality rate (d) is difficult to estimate directly, and context‐specific data are typically weakly informative about it. Nevertheless, natural mortality is potentially an important component of total mortality, particularly if additive to harvest or culling mortality. The natural mortality rate exhibits allometric or life‐history relationships that are invariant across diverse taxonomic groups, and it is valuable to derive estimates on this basis to serve as priors in later Bayesian models, steering parameter uncertainty towards biologically plausible values, and leading to more reliable model predictions and improved management recommendations. We used Bayesian hierarchical modeling and data from the literature to establish informative priors for instantaneous d as predictions scaled from body mass or maximum age. Posterior mean estimates of the scaling parameters of these models were −0.27 (body mass) and −1.07 (maximum age), respectively, conforming to expected values of −0.25 and −1.00. Direct estimates of d from published studies of coyotes (Canis latrans) in southern Texas, fisher (Pekania pennanti) in Sierra Nevada, and slender mongoose (Galerella sanguinea) in the Kalahari Desert were within the credible intervals of predictions for d using both models. We also compared survivorship curves based on model predictions with observed survivorship of red fox (Vulpes vulpes) from a variety of studies in Britain, among which intensity of culling varied markedly. Across all species, there was better support for the d prediction from maximum age, than from body mass. We thus recommend use of maximum age data to establish informative priors for d where possible. Posterior median predictions of d from maximum age were within 0.01–0.14/year of the direct estimates, whereas the differences between direct estimates and predictions from body mass were 0.04–0.27/year. Sensitivity analysis showed trivial effects of between‐sex differences in body mass, and age‐specific mortality, on predictions of d. Differences between body mass and maximum age model predictions were attributed to the relative importance of intrinsic and extrinsic mortality factors in the 2 approaches (i.e., maximum age predictions allowed for extrinsic factors to affect predicted mortality). © 2018 The Wildlife Society.

Estimating density for species conservation: Comparing camera trap spatial count models to genetic spatial capture-recapture models

Density estimation is integral to the effective conservation and management of wildlife. Camera traps in conjunction with spatial capture-recapture (SCR) models have been used to accurately and precisely estimate densities of “marked” wildlife populations comprising identifiable individuals. The emergence of spatial count (SC) models holds promise for cost-effective density estimation of “unmarked” wildlife populations when individuals are not identifiable. We evaluated model agreement, precision, and survey costs, between i) a fully marked approach using SCR models fit using non-invasive genetic data, and ii) an unmarked approach using SC models fit using camera trap data, for a recovering population of the mesocarnivore fisher (Pekania pennanti). The SCR density estimates ranged from 2.95 to 3.42 (2.18–5.19 95% BCI) fishers 100 km−2. The SC density estimates were influenced by their priors, ranging from 0.95 (0.65–2.95 95% BCI) fishers 100 km−2 for the uninformative model to 3.60 (2.01–7.55 95% BCI) fishers 100 km−2 for the model informed by prior knowledge of a 16 km2 fisher home range. We caution against using strongly informative priors but instead recommend using a range of unweighted prior knowledge. Thin detection data was problematic for both SCR and SC models, potentially producing biased low estimates. The total cost of the genetic survey ($47 610) was two-thirds of the camera trap survey ($77 080), or comparable ($75 746) if genetic sampling effort was increased to include sex and trap-behaviour covariates in SCR models. Density estimation of unmarked populations continues to be a series of trade-offs but as methods improve and integrate, so will our estimates.

Genetic monitoring suggests increasing structure following recolonization by fishers

ABSTRACTPopulation bottlenecks, fragmentation, and isolation can have lasting effects on population genetic structure by decreasing diversity and increasing differentiation among regions. Fishers (Pekania pennanti) were extirpated from many regions of Ontario, Canada, in the early twentieth century because of overharvest, habitat loss, and predator control, although the species has since recolonized much of its former range. Between 2001 and 2003, the recolonized population could be split into several genetically distinct clusters likely corresponding to historical trapping refuges. We reassessed the genetic diversity and population structure of fishers approximately 10 years after recolonization to determine whether homogenization had occurred among genetic clusters, and whether hypothesized northward migration had continued following recolonization of southeastern Ontario by fishers from the Adirondack Mountains of New York, USA. We found no significant changes in the uppermost level of genetic structure but did find evidence of increased lower‐level structure and decreased migration throughout the province, contrary to our hypothesis. This may be indicative of a reduction in fisher density or could be due to the population reaching a migration‐drift equilibrium following a period of rapid expansion. Our results highlight the potential importance and utility of continued genetic monitoring following local extirpation and recolonization. Conservation managers can use periodically sampled population genetic information to adapt and update management strategies. © 2018 The Wildlife Society.

Selection of rest structures and microsites by fishers in Oregon

ABSTRACTMost previous studies of resting habitat for fishers (Pekania pennanti) in the Pacific coastal region of the western United States and Canada were focused on habitat conditions within rest sites (typically ≤0.5 ha), which include the rest structure (e.g., live tree, snag, log) at its center. Studies of selection for rest structures were sparse and compared characteristics of rest structures to those occurring within rest sites; none investigated selection by sampling resource availability throughout the study area. In addition, limited data were available on the use of rest microsites (e.g., mistletoe brooms, platform branches, cavities) by fishers, and no studies have quantified their availability. To better inform forest management activities designed to improve resting habitat for fishers, we documented use of rest structures and microsites throughout the year by 12 female and 7 male fishers on the west slope of the Cascade Range in southern Oregon, USA from 1995 to 2001, systematically sampled the availability of rest structures and microsites, and used logistic regression modeling to investigate selection of rest structures. Fishers primarily used live trees (65%), snags (14%), and logs (16%) for resting; in all 3 resulting models, the characteristic that best distinguished used from available rest structures was the presence of a suitable rest microsite: mistletoe broom or cavity in live trees, cavity in snags, and hollow end in logs. Only the snag and log models included covariates associated with tree size, likely reflecting the need for enclosed rest microsites (cavities, hollow ends) to be large enough to contain an adult fisher. We then used our availability data to model the ecological characteristics associated with mistletoe brooms in live trees, cavities in snags, and hollow ends in logs. Whether a tree was a hemlock (Tsuga spp.) had the greatest effect on the presence of suitable mistletoe broom microsites, but the most important characteristics of snags with cavities and logs with hollow ends were being in moderate stages of decay and relatively large in diameter at breast height (snags) or diameter 3 m from the large end (logs). Forest structures containing suitable rest microsites for fishers were uncommon in our study and may represent a limited resource. Accordingly, we recommend that management of resting habitat for fishers be focused on retaining relatively large structures that already contain suitable rest microsites, rather than simply retaining the largest available structures. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Reproductive parameters of the fisher (Pekania pennanti) in the southern Sierra Nevada, California

Quantifying reproductive parameters is essential for developing effective conservation plans for species of concern; however, studying reproduction in wild settings can be challenging and local data are frequently unavailable. The fisher (Pekania pennanti) is an elusive forest-dwelling carnivore of conservation concern that occurs across much of boreal North America and reaches the southernmost limit of its distribution in the southern Sierra Nevada (SSN) in California. Data on fisher reproduction in this region are limited and applicability of parameters from other areas is uncertain. To clarify how fisher populations in the SSN compare with those elsewhere in North America, we conducted a comprehensive review of available literature on reproduction throughout the species’ range in North America. We then compared findings from the review with data we collected during 7 years in the SSN, focusing on the proportion of females reproducing, litter size, and the parturition date. On average across the fisher’s range, the proportion of adult females that reproduced was 0.71 (range: 0.40–1.00; n = 16 studies), litter size was 2.5 (range: 1–4; n = 16 studies), and parturition occurred on 25 March (range: 3 March–17 April; n = 16 studies). In our study area, we tracked 42 adult female fishers, 35 of which reproduced and used 257 reproductive dens (74 natal, 175 maternal, 8 early failures); 0.86 of our females attempted denning (range: 0.79–1.0; n = 93 opportunities) and 0.75 were successful (range: 0.64–1.0; n = 91 opportunities monitored through the den season). Mean litter size was 1.57 (range: 1–3; n = 75 litters) and mean parturition date was 30 March (range: 17 March–12 April; n = 69 natal dens initiated). Female fishers at the southern limit of their distribution in the SSN reproduced at a rate comparable to or higher than elsewhere in North America, but average litter size was the lowest reported for the species. Female fishers in the SSN gave birth at similar or later dates than elsewhere in their range. We explore factors that might explain patterns of variation in fisher reproductive parameters and discuss conservation implications of our findings.

Status of Fishers in Glacier National Park, Montana

Fishers (Pekania pennanti) are a mid-sized forest-dwelling carnivore in the family Mustelidae, once widely distributed across the northern US and Canada. Between 1800 and 1940, they were extirpated across much of their former range through commercial fur harvesting and habitat modification. Glacier National Park (GNP), which maintains a wildlife sighting database containing public and agency sighting and track records of Fishers from 1947 through the present, presumed Fishers extant in the park. Over 2007–2012, GNP made opportunistic efforts to collect Fisher DNA in hair traps but were unsuccessful. In 2013 and 2015, GNP conducted a more intensive effort to document the occurrence of Fishers by systematically placing baited hair traps within putative Fisher habitat across the park. These efforts were also unsuccessful and I show through application of Bayes' Theorem that a resident population of Fishers in GNP is highly improbable. Past credible sightings of Fishers in GNP were probably animals dispersing from occupied habitats to the west of GNP, and I suggest that regular occurrence of deep, unconsolidated winter snow may have prevented Fishers from occupying GNP in the past.