Pacific Martens Research Articles

Climate change differentially alters distribution of two marten species in a hybrid zone.

Species' ranges are shifting rapidly with climate change, altering the composition of biological communities and interactions within and among species. Hybridization is among the species interactions that may change markedly with climate change, yet it is understudied relative to others. We used non-invasive genetic detections to build a maximum entropy species distribution model and investigate the factors that delimit the present and future ranges of American marten (Martes americana) and Pacific marten (Martes caurina) in a contact zone in the Northern Rockies. We found that climate change will decrease the suitable habitat predicted for both species, as well as the amount of overlap in predicted suitable habitat between the species. Interestingly, predicted suitable habitat for Pacific marten extended further north in the study region than our genetic detections for the species, suggesting that biotic factors, such as interactions with American marten, may affect the realized range of this species. Our results suggest that future work investigating the interactions among biotic and abiotic factors that influence hybrid zone dynamics is important for predicting the futures of these two species in this area under climate change.

Ecological displacement in a Rocky Mountain hybrid zone informs management of North American martens (Martes)

ContextParapatric sister species are ideal for tests of ecological interactions. Pacific (Martes caurina) and American pine (M. americana) martens are economically and culturally valuable furbearers that hybridize in the north-central Rocky Mountains. Despite preliminary evidence of biased introgression, the hybrid zone has been geographically stable for 70 years, but interspecific ecological interactions have yet to be examined in detail.ObjectivesWe test whether ecological interactions may influence the outcome of hybridization in this system. To that end, we estimate the fundamental niche of each species and gauge how suitability landscapes change when the two species are in contact.MethodsWe genotyped > 400 martens from the Rocky Mountain hybrid zone to diagnose individuals to species-level and identify putative hybrids. We then built range-wide ecological niche models for each species, excluding individuals in the hybrid zone, to approximate their respective fundamental niches. Those models were projected into the hybrid zone and compared with niche models trained on individuals within the hybrid zone to assess how niche dynamics change when the species are in sympatry.ResultsThe fundamental niche of each species differed significantly, while the hybrid zone was equally suitable for both. Niches of each species based on models built within the hybrid zone showed that Pacific martens utilized significantly less suitable habitat than expected based on their range-wide fundamental niche, suggesting that species interactions shape local hybridization. We detected few admixed individuals (12%), with no evidence of directional (sex or species) biases. Interstate-90 further acts as a major dispersal barrier.ConclusionsNorth American martens are currently managed as a single species by some state agencies, yet significant ecological and genetic differences indicate they should be managed separately. The observed ecological displacement of Pacific martens by American pine martens may partially explain the mixed success of historical, mixed-species wildlife translocations and cautions such translocations in the future. Landscape-scale consideration of ecological dynamics, in addition to molecular compatibility, will be essential to the success of future translocations.

Effects of burn severity and postfire salvage logging on carnivore communities in montane forests

Abstract Wildfire and postfire salvage logging are major drivers of forest succession in western North America. Although postfire landscapes support a variety of carnivore species, it is unclear how these animals respond to differing patterns and severities of burning, or to additional landscape change from postfire salvage logging. Open, early-seral habitats created by these disturbances are predicted to benefit generalists such as coyotes (Canis latrans) and weasels (Mustela spp.), but restrict the activity of forest specialists such as Canadaian Lynx (Lynx canadensis) and Pacific Marten (Martes caurina). We used winter track surveys, supplemented with remote cameras, to examine carnivore habitat use in and around large, mixed-severity burns in north-central Washington, United States (burned in 2006), and central British Columbia, Canada (burned in 2010, then partially salvage-logged; some areas reburned in 2017). At 10 to 13 years postfire, marten had similar detection rates across lightly and severely burned areas of the 2006 burn, as did coyotes. Marten selected lightly burned areas of the 2010 burn (6 to 9 years postfire) over higher burn severities, and selected burns over adjacent unburned forests. Weasels selected areas of higher burn severity on both landscapes, while Lynx selected lower burn severities. Weasels and coyotes selected areas with a greater proportion of salvage-logged habitat in the 2010 burn, while marten, lynx, and wolves (Canis lupus) avoided areas with salvage logging. Fishers (Pekania pennanti) showed no clear patterns of selection or avoidance in relation to burn severity or salvage logging. Burn severity strongly influences wildlife activity postfire; lightly burned residual habitats are critical for forest specialists. Postfire salvage logging alters carnivore communities and may hinder species that require structurally complex landscapes.

Development of a non-invasive method for species and sex identification of rare forest carnivores using footprint identification technology

Many wildlife species have sex specific habitat requirements. Due to the unique requirements for birthing and raising offspring, female reproductive habitat is often a limiting factor for a population and has been identified as a priority for conservation. Therefore, the ability to detect where females persist on the landscape and identify these potential reproductive areas is essential in creating effective conservation strategies. Here we describe the development of a non-invasive method to identify species and sex based on track images collected at track plate stations using footprint identification technology (FIT). We developed this technique using data from the southern Sierra Nevada fisher (Pekania pennanti) population and a co-occurring species of conservation concern the Pacific marten (Martes caurina). We coupled track plate footprints with non-invasive genetic samples and camera trap images to create a reference dataset of known species for fisher and marten and known sex for fisher. We used FIT to geo-reference 167 marten and 367 fisher tracks (34 males, 27 females) using 7 landmark points and then extracted 124 morphometric variables (distances, angles, and areas) for use in identifying species and sex for fisher using linear discriminant analyses. Using a single variable, we found species classification accuracy >99% in distinguishing fisher from marten. For fisher sex identification our most parsimonious model consisting of only 2 variables achieved an accuracy of 94.0% for the training set and 89.4% for the test set. We also report a method to quantify classification uncertainty for each track. This method provides a rapid, cost effective, entirely non-invasive method to accurately identify sex that can easily be implemented in field studies.

Divergent or convergent: how do forest carnivores use time in the Greater Yellowstone Ecosystem?

Abstract Divergent activity can change the intensity of species interactions, largely affecting species distributions and abundances, and consequently influencing the composition and function of ecological communities. Few assessments of activity patterns have focused questions around different resource constraints or have examined varying time frames when interaction strengths are expected to increase. We evaluated how activity among carnivores and their prey shifted from early to late winter, coinciding with a presumed decrease in food resources for carnivores, and we measured time between species detections within a camera station. Our study species were three forest carnivores—Pacific martens (Martes caurina), Rocky Mountain red foxes (Vulpes vulpes macroura), coyotes (Canis latrans); and two of their prey—American red squirrels (Tamiasciurus hudsonicus), and snowshoe hares (Lepus americanus). We sampled these species across an extensive network of cameras (n = 107) during the 2014–2017 winter seasons in the Greater Yellowstone Ecosystem, Wyoming. We generated kernel density plots for timing of photographs and calculated the coefficient of overlap among density plots for our predators and prey during early and late winter. Furthermore, we calculated the time-between-detections (i.e., hours) among forest carnivores. We found no consistent trends in time-between-detections across our species pairs. Pacific martens exhibited cathemeral activity that aligned with the peaks in activity of the two prey species. Temporal overlap between coyote and red fox activities was small in early winter, whereas coyotes modified activity in late winter such that they more closely aligned with red foxes. This intraguild convergence of activity may reflect an increase in resource constraints and have consequences for competitive interactions between these two canids. Our study supports the notion that variation in time is an important axis in facilitating coexistence among these forest carnivores and prey species.

Structural complexity characterizes fine‐scale forest conditions used by Pacific martens

AbstractWhen wildlife species exhibit unexpected associations with vegetation, replication of studies in different locales can illuminate whether patterns of use are consistent or divergent. Our objective was to describe fine‐scale forest conditions used by Pacific martens (Martes caurina) at 2 study sites in northern California that differed in forest composition and past timber harvest. We identified denning and resting locations of radio‐marked martens and sampled structure‐ and plot‐level vegetation using standardized forest inventory methods between 2009–2021. Woody structures used by martens were significantly larger than randomly available structures across types (e.g., live tree, snag, log) and at both study sites. Den and rest structures occurred in areas characterized by higher numbers of logs and snags, lower numbers of live trees and stumps, larger diameter live trees and logs, and greater variation in live tree and log diameter. Features of denning and resting locations were largely consistent across study sites and were generally representative of fine‐scale forest heterogeneity and increased structural complexity, conditions that martens have been widely associated with at broader spatial scales (i.e., home range or landscape). The spatial occurrence of denning and resting locations may indicate that fine‐scale structural complexity facilitates marten foraging while reducing predation risk. Our work offers timely and directed information that can guide forest management in the context of increased landscape change.

Spaceborne LiDAR and animal-environment relationships: An assessment for forest carnivores and their prey in the Greater Yellowstone Ecosystem

Animal conservation requires understanding animal-habitat relationships. The integration of novel remote sensing platforms such as Light Detection and Ranging (LiDAR) technology has dramatically improved the resolution of insight when evaluating animal-habitat relationships by characterizing forest structure. However, conventional LiDAR collection (e.g., airborne or terrestrial laser scanning) may be limited by small spatial extents and logistical constraints (e.g., budget) associated with sampling. NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission provides an alternative and complement to conventional LiDAR sampling with globally available waveform LiDAR, which is being collected to characterize vertical and horizontal structure of Earth’s forests. Forest carnivores are wide-ranging species occupying forested ecosystems, and are generally associated with vertical and horizontal forest structure for their survival and reproduction. We evaluated patterns in occurrence and habitat use of forest carnivores, which included Pacific martens (Martes caurina), Rocky Mountain red foxes (Vulpes vulpes macroura), and coyotes (Canis latrans) and patterns in occurrence of their prey; American red squirrels (Tamiasciurus hudsonicus) and snowshoe hares (Lepus americanus). Camera trap data were collected during the 2014–2017 winters in the Greater Yellowstone Ecosystem in Wyoming, USA. Our objectives were to (1) combine GEDI samples with multispectral satellite imagery from Landsat 8 to upscale vertical forest structure metrics; (2) assess the relative importance of environmental characteristics influencing occurrence and habitat use of forest-associated predators and prey; and (3) determine if GEDI-derived variables aided our efforts in characterizing animal-environment relationships. We used Random Forest regression models to upscale GEDI samples across our study area and implemented a multi-tiered approach using generalized linear mixed effect models to simultaneously evaluate animal-environment relationships and how GEDI-derived metrics improved the animal-habitat models. GEDI-derived metrics of relative height and foliage height diversity improved our animal-environment models and were among the strongest covariates (effect sizes were 1.3–1.8 times larger than the next closest) in the coyote, red squirrel, and snowshoe hare models. All five species were influenced to some degree by the frequency of rebaiting a camera trap and varying conditions of snow depth. Collectively, our work indicates forest canopy height and complexity variables significantly improved our ability to assess the importance of forest characteristics on forest carnivores and their prey. Indeed, there is an untapped opportunity to enhance animal ecology and conservation planning with continued integration of GEDI information with freely available satellite data to characterize attributes of forest structure across expansive areas.

Combined field and clinical methods clarify mortality causes and survival patterns of Pacific martens

AbstractQuantifying the demography of wildlife populations is imperative to evaluating population trends. Understanding patterns of influential demographic parameters often requires investigation of mechanisms influencing demography, which can be difficult to determine for cryptic species. We radio‐tracked Pacific martens (Martes caurina), a small‐bodied and elusive mesocarnivore, to estimate survival, determine causes of mortality, and assess co‐occurring pathological conditions. We tracked 18 female and 33 male martens for an average (±SD, range) of 16.35 months (±8.7, 1–41) from 2009–2013 and 2015–2017 in northern California. Annual survival rates were 0.81 (95% CI = 0.66–0.95) and 0.68 (95% CI = 0.57–0.79) for female and male martens, respectively. We documented 16 marten mortalities, 13 of which were suspected predation events. Seven mortalities were empirically linked to predation via clinical forensic evidence, with bobcats (Lynx rufus; n = 5) representing the majority of predator species identified. The proximate cause of mortality for 1 marten was attributed to toxicosis from anticoagulant rodenticide exposure, which has not been previously reported in free‐ranging martens. Our findings suggest the timing of marten mortality aligned with reproductive periods that incurred increased energetic requirements, which may result in increased predation risk. We propose continued pairing of field and clinical assessments to better substantiate mortality sources of wildlife, elucidate underlying pathology, and identify novel stressors.

Residual forest structure influences behaviour of Pacific marten (

Wildfires are broad-scale disturbances in North American forests, with impacts that persist for many decades. Further disturbance from post-fire salvage logging is extensively modifying burned landscapes. The removal of habitat structure by fire and salvage logging may affect the persistence of forest-specialist wildlife such as Pacific marten (Martes caurina). However, it is unclear which resources are important to marten on burned landscapes. We used snow tracking and habitat surveys to examine marten habitat selection after three large fires in north-central Washington, USA (10–13 years post-fire), and central British Columbia, Canada (1–2 and 6–9 years post-fire). We developed site-scale habitat models to explain marten foraging and scent-marking post-fire, and assessed further structural changes from salvage logging. Foraging marten chose sites with lower burn severity, greater canopy closure, more vertical structures (trees, snags, saplings, and shrubs), and greater moss/lichen cover than what was generally available. When scent-marking, marten selected structurally-complex sites with abundant deadfall or saplings. Marten moved more quickly when canopy cover was sparse, and rarely used salvage-logged areas. Our results suggest that marten rely on residual habitat structure within large burns, and that secondary disturbance from salvage logging is substantially more harmful to marten than the original fire.

Evaluating the effects of alternative landscape management scenarios on three old-forest-associated predators over 100 years in the fire-prone forests of the Sierra Nevada, USA

Developing and implementing landscape-scale management strategies capable of balancing the need for restoring natural fire regimes and promoting ecosystem resiliency for future climate change remains an urgent need globally. To help guide development of a landscape management strategy capable of meeting multiple objectives, five alternative landscape management scenarios for reducing the risk of uncharacteristically severe wildfire using thinning or managed and prescribed wildfire were developed by local forest managers in the Lake Tahoe region of the Sierra Nevada mountains. Effects of each scenario on forest structure, composition, and wildfire behavior were simulated over a 100-year period using the dynamic landscape simulation model LANDIS-II. We developed empirical territory occurrence models for three old-forest-associated predators, using 22 California Spotted Owl, 28 Northern Goshawk, and 16 female Pacific marten territories and presence-only modeling to evaluate the effects of each management scenario. The recruitment of more old-forest habitat across the simulated landscape was a more significant factor than any differences in the management scenarios, resulting in increases in the numbers of territories for all three predators, regardless of scenario. Increases in the numbers of territories were slowed in Scenario 4, which had the greatest amount of thinning, but the positive trend continued decades beyond when the other scenarios began to show a decline in territory numbers from severe wildfire. However, increases in the numbers of territories over time were slowed and overall were the lowest for the two old-forest predators that were most sensitive to the amount of old forest at the territory scale in the scenario with the greatest pace and scale of treatments. This suggests a trade-off between slowing the increase in the numbers of territories in the short term from forest growth by using fuels treatments with increased pace and scale to create forest structure that is less susceptible to severe wildfire in the long term, and that these management scenarios may need to be re-evaluated in 50 years before committing to continuing management efforts that may ultimately become detrimental for old-forest predators within 100 years.

Post-fire movements of Pacific marten (Martes caurina) depend on the severity of landscape change

BackgroundWildfires and forestry activities such as post-fire salvage logging are altering North American forests on a massive scale. Habitat change and fragmentation on forested landscapes may threaten forest specialists, such as Pacific marten (Martes caurina), that require closed, connected, and highly structured habitats. Although marten use burned landscapes, it is unclear how these animals respond to differing burn severities, or how well they tolerate additional landscape change from salvage logging.MethodsWe used snow tracking and GPS collars to examine marten movements in three large burns in north-central Washington, USA (burned in 2006) and central British Columbia, Canada (burned in 2010 and 2017). We also assessed marten habitat use in relation to areas salvage-logged in the 2010 burn. We evaluated marten path characteristics in relation to post-fire habitat quality, including shifts in behaviour when crossing severely-disturbed habitats. Using GPS locations, we investigated marten home range characteristics and habitat selection in relation to forest cover, burn severity, and salvage logging.ResultsMarten in the 2006 burn shifted from random to directed movement in areas burned at high severity; in BC, they chose highly straight paths when crossing salvage-blocks and meadows. Collared marten structured their home ranges around forest cover and burn severity, avoiding sparsely-covered habitats and selecting areas burned at low severity. Marten selected areas farther from roads in both Washington and BC, selected areas closer to water in the 2006 burn, and strongly avoided salvage-logged areas of the 2010 burn. Marten home ranges overlapped extensively, including two males tracked concurrently in the 2010 burn.ConclusionsAreas burned at low severity provide critical habitat for marten post-fire. Encouragingly, our results indicate that both male and female marten can maintain home ranges in large burns and use a wide range of post-fire conditions. However, salvage-logged areas are not suitable for marten and may represent significant barriers to foraging and dispersal.

Predicted distribution of a rare and understudied forest carnivore: Humboldt marten (Martes caurina humboldtensis).

BackgroundMany mammalian species have experienced range contractions. Following a reduction in distribution that has resulted in apparently small and disjunct populations, the Humboldt marten (Martes caurina humboldtensis) was recently designated as federally Threatened and state Endangered. This subspecies of Pacific marten occurring in coastal Oregon and northern California, also known as coastal martens, appear unlike martens that occur in snow-associated regions in that vegetation associations appear to differ widely between Humboldt marten populations. We expected current distributions represent realized niches, but estimating factors associated with long-term occurrence was challenging for this rare and little-known species. Here, we assessed the predicted contemporary distribution of Humboldt martens and interpret our findings as hypotheses correlated with the subspecies’ niche to inform strategic conservation actions.MethodsWe modeled Humboldt marten distribution using a maximum entropy (Maxent) approach. We spatially-thinned 10,229 marten locations collected from 1996–2020 by applying a minimum distance of 500-m between locations, resulting in 384 locations used to assess correlations of marten occurrence with biotic and abiotic variables. We independently optimized the spatial scale of each variable and focused development of model variables on biotic associations (e.g., hypothesized relationships with forest conditions), given that abiotic factors such as precipitation are largely static and not alterable within a management context.ResultsHumboldt marten locations were positively associated with increased shrub cover (salal (Gautheria shallon)), mast producing trees (e.g., tanoak, Notholithocarpus densiflorus), increased pine (Pinus sp.) proportion of total basal area, annual precipitation at home-range spatial scales, low and high amounts of canopy cover and slope, and cooler August temperatures. Unlike other recent literature, we found little evidence that Humboldt martens were associated with old-growth structural indices. This case study provides an example of how limited information on rare or lesser-known species can lead to differing interpretations, emphasizing the need for study-level replication in ecology. Humboldt marten conservation would benefit from continued survey effort to clarify range extent, population sizes, and fine-scale habitat use.

Comparative Reproductive Ecology of Two Subspecies of Pacific Marten (Martes caurina) in California

Accurate information on reproductive ecology is necessary to develop conservation actions for at-risk wildlife species. Our objective was to describe female reproductive parameters and den use of two subspecies of wild, untrapped Pacific martens (Humboldt marten, Martes caurina humboldtensis; Sierran marten, M. c. sierrae) of conservation interest in California. We used radio telemetry and remotely triggered cameras to monitor 10 Humboldt martens (2014 to 2016) and six Sierran martens (2016 to 2017) over 23 total denning periods. For Humboldt martens, mean parturition date was 13 April, proportion of adult females reproducing was 80% (n = 12 of 15), and mean litter size was 1.8 ± 0.6 kits (x̄ ± SD). For Sierran martens, mean parturition date was 29 April, proportion of adult females reproducing was 87% (n = 7 of 8), and mean litter size was 1.9 ± 0.7 kits. Humboldt and Sierran marten dens were predominantly located in woody structures, with live trees, snags, and logs comprising 91% and 79% of dens, respectively. Although reproductive ecologies of Humboldt and Sierran martens were largely similar, Sierran marten parturition dates were significantly later. We compare our study populations to other North American marten populations and examine factors that could influence consistency or variability in reproductive parameters between populations.

Resource use by an apex mesocarnivore, Pacific marten, in a highly modified forested island ecosystem

Apex mesocarnivores can have a large influence on the functioning of plant and animal communities. Such effects can be more pronounced in relatively depauperate island ecosystems, especially in the context of a legacy of landscape change and introduced species. One such ecosystem is Haida Gwaii, British Columbia, Canada, where a long history of introduced species and forest harvesting has greatly influenced the composition of the plant and animal communities. Most notably, Sitka black-tailed deer (Odocoileus hemionus sitkensis), an introduced and unchecked invasive species, has interacted with forest harvesting to greatly change the understory structure and composition of those temperate rainforests. Little is known of the habitat ecology of Pacific marten (Martes caurina), the small-bodied apex predator on those islands. We used camera traps to monitor the distribution and habitat ecology of marten across 2 winters. We used mixed-effects logistic regression to test 14 a priori hypotheses represented by statistical models formulated at two spatial scales (100 and 1000 m), with four categories of explanatory factors: sampling bias, forest structure, topography, and human disturbance. Relationships between detections and covariates from the top models revealed that at the 100-m scale, marten were more likely to use habitat that was closer to streams and marine shorelines and that contained a small area of forest harvesting. Marten detections were associated with habitat containing some component of forest edge and road, suggesting foraging behavior adapted to invasive deer, an important source of carrion for marten during winter. The broad use of habitats by Pacific marten suggests that intraguild competition and predation might occur with several species at risk including the endemic Haida ermine (Mustela ermine haidarum). Those two species would likely overlap in diet and distribution when co-occurring across low-elevation coastal habitats. Conservation planning on Haida Gwaii should consider measures that decrease the potential for competition or predation between marten and species at risk.

Whole‐genome resequencing reveals persistence of forest‐associated mammals in Late Pleistocene refugia along North America’s North Pacific Coast

AbstractAimNumerous glacial refugia have been hypothesized along North America's North Pacific Coast that may have increased divergence of refugial taxa, leading to elevated endemism and subsequently clustered hybrid zones following deglaciation. The locations and community composition of these ice‐free areas remains controversial, but whole‐genome sequences now enable detailed analysis of the demographic and evolutionary histories of refugial taxa. Here, we use genomic data to test spatial and temporal processes of diversification among martens with respect to the Coastal Refugium Hypothesis, to understand the role of climate cycling in shaping diversity across complex landscapes.LocationNorth America and North Pacific Coast archipelagos.TaxonNorth American martens (Martes).MethodsShort‐read whole‐genome resequencing data were generated for 11 martens: four M. americana, four M. caurina, two hybrids, and one outgroup (Martes zibellina). Sampling was representative of known genetic clades within New World martens, including sampling within insular and continental hybrid zones and along the North Pacific Coast (five island populations). ADMIXTURE, F‐statistics, and D‐statistics (ABBA‐BABA) were used to identify introgression and infer directionality. Heterozygosity densities, estimated via PSMC, were used to characterize historical demography at and below the species level to infer refugial and colonization processes.ResultsForest‐associated Pacific martens (M. caurina) are divided into distinct insular and continental clades consistent with the Coastal Refugium Hypothesis. There was no evidence of introgression on islands that received historical translocations of American pine martens (M. americana), but introgression was detected in two active zones of secondary contact: one insular and one continental. Only early‐generational hybrids were identified across multiple hybrid zones, a pattern consistent with potential genetic swamping of M. caurina by M. americana.Main conclusionsDespite an incomplete fossil record, genomic evidence supports the persistence of forest‐associated martens, likely the insular Pacific marten lineage, along the western edges of the Alexander Archipelago during the Last Glacial Maximum. This discovery informs our understanding of refugial paleoenvironments, critical to interpreting refugial timing, duration, and community composition. Genomic reevaluations of other taxa along North America's North Pacific Coast may yield new and deeper perspectives on the history of refugial forest communities and the role of dynamic climate shifts in shaping high‐latitude diversity across complex insular landscapes.

Spatial and temporal variability in the diet of Pacific marten (Martes caurina) on Haida Gwaii: an apex predator in a highly modified ecosystem

Knowledge of the diet ecology of apex predators in insular island ecosystems has direct applications to the conservation of endemic species at risk of extinction. We used stable isotopes of carbon and nitrogen to infer resource-use strategies of an indigenous predator, the Pacific marten (Martes caurina (Merriam, 1890)), in a highly modified ecosystem on Haida Gwaii, British Columbia, Canada. We used Bayesian isotopic mixing models to estimate the relative contributions of different food sources to marten diet across seasons and during overall lifetime, and to determine how diet varied with different levels of access to marine resources. Isotopes of carbon and nitrogen measured in hair and muscle tissue suggested that marten consumed salmon (3%–17%) and berries (25%–37%) seasonally; these diet groups were relatively minor components of the lifetime diet. Analysis of bone collagen suggested that terrestrial fauna — including birds, deer, small mammals, and invertebrates — contributed the most to diet (41%–55%), and marine invertebrates (38%–48%), not salmon (0%–3%), were the main allochthonous marine nutrient subsidy to lifetime diet. Plasticity in foraging ecology, combined with a broad dietary niche, introduced prey, notably the invasive Sitka black-tailed deer (Odocoileus hemionus sitkensis Merriam, 1898), as well as abundant marine resources, may allow marten to outcompete other indigenous and endemic carnivores on Haida Gwaii.

Landscape seasonality influences the resource selection of a snow-adapted forest carnivore, the Pacific marten

Characterizing animal space-use and resource selection is central to effective conservation. In seasonally variable systems, animals may alter space-use to minimize risk, mediate physiological costs, and maintain access to resources. However, it is often unclear which environmental features influence space-use across seasons, and whether resource selection of non-migratory animals varies in seasonally snow-covered environments. We quantified space-use and scale-dependent resource selection of Pacific martens (Martes caurina) in northern California to evaluate the relative influence of abiotic (e.g., topography, weather) and biotic (e.g., forest structure) covariates on spatial ecology of martens in ecologically distinct seasons (i.e., snow-covered, snow-free). We obtained fine-scale location data from GPS-collared martens (n = 26) in the Cascade and Sierra Nevada mountain ranges in California, USA. We incorporated spatially explicit weather, topographic, and forest structure data in a scale-optimized, seasonal resource selection function framework to determine the relative importance of abiotic and biotic conditions during snow-covered and snow-free periods. During snow-free periods, martens selected for features associated with complex forest structure, including increasing stem basal area. Conversely, space-use was associated with dense forest structure and topographic features in snow-covered periods. Though the relative influence of abiotic and biotic covariates on resource selection varied by season, the scale at which these variables best explained space-use did not. Our results highlight seasonality and scale-dependence of resource selection by martens and emphasize the importance of understanding spatio-temporal responses of free-ranging animals to landscape heterogeneity. We suggest behavioral or ecological requirements that differ by season and scale may influence space-use and resource selection patterns, and, consequently, can inform conservation actions.

Pliocene-Early Pleistocene Geological Events Structure Pacific Martens (Martes caurina).

The complex topography, climate, and geological history of Western North America have shaped contemporary patterns of biodiversity and species distributions in the region. Pacific martens (Martes caurina) are distributed along the northern Pacific Coast of North America with disjunct populations found throughout the Northwestern Forested Mountains and Marine West Coast Forest ecoregions of the West Coast. Martes in this region have been classified into subspecies; however, the subspecific designation has been extensively debated. In this study, we use genomic data to delineate conservation units of Pacific marten in the Sierra-Cascade-Coastal montane belt in the western United States. We analyzed the mitochondrial genome for 94 individuals to evaluate the spatial distribution and divergence times of major lineages. We further genotyped 401 individuals at 13 microsatellite loci to investigate major patterns of population structure. Both nuclear and mitochondrial DNA suggest substantial genetic substructure concordant with historical subspecies designations. Our results revealed that the region contains 2 distinct mitochondrial lineages: a Cascades/Sierra lineage that diverged from the Cascades/coastal lineage 2.23 (1.48-3.14 mya), consistent with orogeny of the Cascade Mountain chain. Interestingly, Pacific Martes share phylogeographic patterns similar with other sympatric taxa, suggesting that the complex geological history has shaped the biota of this region. The information is critical for conservation and management efforts, and further investigation of adaptive diversity is warranted following appropriate revision of conservation management designations.

Forest structure and snow depth alter the movement patterns and subsequent expenditures of a forest carnivore, the Pacific marten

Energetic balance is central to the survival and persistence of free‐ranging animals. Quantifying expenditures and identifying factors that drive energetics informs our understanding of species' ecology and their responses to shifting environmental conditions. Approaches used to estimate energetic expenditures of free‐ranging species, such as doubly‐labelled water (DLW), are precise but difficult to implement. Global positioning system (GPS) collars and accelerometers have emerged as alternatives for estimating expenditures, but these techniques have few applications in terrestrial species and no applications in small‐bodied (<5 kg) terrestrial animals. Here, we estimated movement characteristics and field metabolic rates (FMR) of Pacific martens Martes caurina, a small‐bodied carnivore with relatively high energetic costs, in a heterogeneous landscape to explore the role of movement and landscape characteristics in energetics. We concurrently used DLW and GPS collars to investigate the relationship between movement characteristics and FMR. Movement velocity explained the greatest amount of variation in mass‐specific FMR and we used this relationship to predict expenditures of previously collared martens. We found that predicted mass‐specific FMR was highest among males and increased in open patches primarily as a result of increased velocity and more erratic movements. Additionally, martens moving through deep snow also exhibited increased FMR. Our work shows movement metrics can effectively explain variation in FMR and identify landscape features, like forest structure and snow depth, that influence movements with cascading effects on energetics for free‐ranging mammals in rapidly changing systems.

Using fine scale resolution vegetation data from LiDAR and ground-based sampling to predict Pacific marten resting habitat at multiple spatial scales

Pacific marten (Martes caurina) populations have become fragmented and constricted throughout their western range, often due to factors such as increased severity of wildfires and timber harvesting. Future population declines are predicted given decreasing snow packs and changes in vegetation communities. One element of marten habitat, rest and den structures, may be particularly vulnerable. These structures are used for protection from inclement weather and predation, as well as sites for parturition. Rest structures are often considered a limiting habitat element; characterizing their abundance, type, and distribution has been suggested as a way to evaluate habitat quality. We evaluated marten resting habitat, combining vegetation data from light detection and ranging technology (LiDAR) and ground-based surveys. From 2009–2013 and 2015–2017, we located 312 unique rest structures used by 31 martens (18 males, 13 females). With ground-based surveys, we examined selection of used structures by measuring the diameter at breast height for comparison of rest structures and trees located in random plots. For broader landscape-level predicted habitat, we paired used locations with 624 randomly-sampled locations, and optimized 14 habitat covariates at 12 spatial scales using case-controlled logistic regression. Each covariate’s optimized scale was used to develop a series of a priori hypothesized multi-scale habitat selection models. Martens selected woody structures that were larger than random structures (rest structures = 97.8 ± 31.0 cm; random = 52.7 ± 24.9 cm, x̅ ± SD, t = 21.6, p < 0.001). Marten habitat selection was also positively associated with increased canopy cover and structural complexity within 270 m radius of suitable rest structures and increased tree cover at the broadest scale evaluated (990 m). Our models revealed elevation was positively correlated with predicted marten resting habitat; average elevation at our used sites was 1940 m. Finally, our model depicted areas of predicted habitat near road systems, but we assumed this was an artifact from our sampling bias. Because both canopy cover and structural complexity were optimized at a 270 m radius, this may be an appropriate scale to consider for management activities such as establishing leave islands or focal areas of restoration. We provide one of the first evaluations of marten habitat incorporating the use of LiDAR, which can be broadly and accurately extrapolated for management planning and restoration prioritization.