Large, high-severity fire frequency has drastically increased in recent decades in dry conifer forests of the western United States, yet species’ responses to fire are poorly understood, particularly for marten. To address this paucity, we assessed post-fire space use by Pacific marten (Martes caurina), a forest-obligate carnivore, in California (Dixie Fire; 2021) and Oregon (Flat Fire; 2023). Using GPS collar data collected in 2024, we calculated marten use-areas (size, burn severity composition) and examined marten use of burns (Manly-Chesson index; α>1 = selection, α<1 = avoidance). Male and female marten use-areas were 5.25±1.81 (average±SD; n=10) and 4.19 km2 (n=1), respectively. Unburned forest comprised the highest proportion of use-areas (58±29%) with variation across severities (low = 14±7%, moderate-low = 9±7%, moderate-high = 9±9%, high = 11±9%). Marten exhibited weak selection of unburned forest (α = 1.24±0.30) and avoidance of high severity burn patches (α = 0.29±0.37). Our data suggest marten are using a full gradient of burn severities; this is unexpected given that large, high-severity fires typically degrade forest structure features important to marten. Future studies examining whether martens are capable of long-term persistence in post-fire landscapes will be valuable for developing informed forest management practices and species conservation strategies.

Coastal marten (Martes caurina humboldtensis) require multiple structures (e.g., trees, snags, logs) within home ranges for resting and denning, often serving as locations to avoid predators or mitigate adverse weather conditions. Land managers urgently seek vegetation information to identify risks between fuel-focused forest treatments and conservation of essential areas used by martens. We identified 88 resting locations (n = 18 martens) using both fine-scale GPS/accelerometer data or VHF telemetry in southern Oregon. We collected plot-level conditions (basal area, shrub and horizontal cover, woody material, slash/rock pile volume, canopy cover, foliage height diversity, plant area volume density) at used and random locations (n = 76, 74, respectively). Preliminarily, area of both slash and rock piles were higher at used than random locations (slash: 165±1409 m3, 5±33 m3; rock: 9,422±81,317 m3,11±40 m3, respectively). Shrub and horizontal cover were also modestly higher at used than random locations (shrub: 52±20%, 39±23%; horizontal cover: 78±16%, 68±19%, respectively). However, our confidence intervals overlapped, and summarizing vegetation metrics resulted in weak correlations of marten use. Moving forward, we will use machine learning to build decision trees describing selection. Our results highlight challenges of describing coastal marten habitat even within a relatively homogenous study area.

To mitigate worsening fire severity in the western United States, forest managers are increasingly thinning tree stands to reduce available fuels. These treatments have the potential to disrupt the movements and habitat of Pacific marten (Martes caurina), who prefer multistory, dense conifer vegetation. We analyzed the movements from 32 GPS-collared martens within Lassen National Forest, between 2010 and 2019, to provide actionable recommendations to managers looking to lessen the impacts of forest-thinning treatments on martens. We categorized each stand in the study area by structural complexity: complex (i.e., dense), simple managed (i.e., thinned dense stands), simple (i.e., thinned or naturally sparse), and open (i.e., little or no cover canopy). We found that martens selected territories comprising a few large complex and simple managed stands and many small simple and open stands. Within their territories, they preferred large complex and simple managed stands; however, preference between the four stand types was indiscernible at smaller patch sizes. This indicates that complex and simple managed patches of these smaller areas could be good targets for fuel-thinning treatments. With additional analyses, we offer forest managers guidelines for area, shape, and location of thinned stands that minimize disruption of marten habitat.

Many forest-dependent species evolved in disturbance-prone landscapes, with intermittent, low-severity disturbances producing heterogeneous conditions to support their persistence. However, fire suppression and climate change have altered disturbance regimes and drought cycles, resulting in larger, higher severity wildfires and extensive drought-induced tree mortality. Fishers (Pekania pennanti) are a forest-dwelling species often associated with late-seral, complex forests and are sensitive to losses in canopy and forest cover resultant from landscape disturbance. In the southern Sierra Nevada, fishers occur within a federally-endangered distinct population segment and recent landscape-scale tree mortality and increasing risk of high-severity wildfire are persistent threats to their recovery. Here, we estimated the contemporary abundance, density, and distribution of fishers in the southern and central Sierra Nevada, in the area encompassing Sequoia, Kings Canyon, and Yosemite National Parks. We incorporated live-capture, remote camera, and telemetry data into integrated spatial-capture recapture models to estimate fisher abundance and density, and simulated the effects of 1) prescribed fire intended to restore ecosystem function and 2) stochastic wildfires at varying severities and spatial extents. We further incorporated these data and detection-nondetection monitoring data into an integrated occupancy model to estimate structural and landscape features that shape the contemporary distribution of fishers. Through this work, we identify forest structure and landscape conditions associated with the distribution of imperiled fishers, and elucidate the putative, differential effects of prescribed and stochastic fire on their persistence.

The Humboldt marten (Martes caurina humboldtensis) was listed as federally threatened in 2020. Coastal marten occur in small, isolated populations in Oregon and California and are currently threatened with habitat loss, catastrophic wildfire, and threats inherent to small populations. The Endangered Species Act (ESA) of 1973 was a visionary framework designed around protecting species and implementing recovery actions using science-based decision-making. Each section of the ESA contributes towards recovery goals and facilitates collaboration between land managers and researchers. This case study will examine how various sections of the ESA are intended to work in concert to conserve Humboldt marten and their habitat and the challenges with using science to support policy.

Effective wildlife management and conservation requires knowledge of a species or population’s natural history, demography, habitat use, and potential risks for management action or inaction. Using a combination of non-invasive surveys, telemetry, GPS movement data, and directed experiments, we evaluated the distribution, population vulnerability, genomics, and perceived risk and foraging behavior of Humboldt martens (Martes caurina humboldtensis), an endangered subspecies of Pacific marten. Despite working with a team of esteemed scientists to provide extensive information relatively quickly, exterior timelines and resource limitations required assumptions to be made about the natural history and behavior of this elusive subspecies. We provide historical context, highlight current knowledge and persistent gaps, and provide a hopeful vision for future collaborations. Some achievable goals include being kind, using innovative ways to share data, and focusing on prospective meta-analysis by adopting common protocols.