Conservation of at-risk species often requires rapid status assessments and timely policy decisions. However, conservation policy implementation (e.g., species listings) may precede data availability and decisions are often based on sparse, uncertain, or potentially flawed information. Here, we present a case study on Humboldt martens (Martes caurina humboldtensis), rare and cryptic carnivores that occur in coastal forests of California and Oregon. Humboldt martens, and the analogous coastal distinct population segment of Pacific martens, were recently listed as state endangered (California, 2019) and federally threatened (2020), yet little is known about many aspects of Humboldt marten population ecology. We modeled population growth of a Humboldt marten population in northern California, incorporating empirically-derived demographic data under a variety of scenarios. All scenarios indicated substantial variability in population growth trajectories as an artifact of highly variable survival estimates. Our work exemplifies the issues of using sparse data to inform conservation decisions, and we provide a framework to improve outcomes of future research efforts of poorly-understood species. We suggest that increased collaboration, purposeful study designs, use of standardized protocols, application of emerging technologies, and data sharing via public repositories are reliable actions that can better produce biologically relevant results and inform future conservation efforts.

Humboldt martens (Martes caurina humboldtensis), a subspecies of Pacific martens, occur in coastal Oregon and California and were designated as federally threatened and state Endangered (California). We assessed martens’ predicted distribution and interpret our findings as hypotheses correlated with the subspecies’ niche to inform strategic conservation actions. We spatially-thinned 10,229 locations collected 1996–2020 by applying a minimum distance of 500-m between locations, resulting in 384 locations. We independently optimized the spatial scale of each variable and used MaxEnt to create a predicted distribution. Humboldt marten locations were positively associated with increased shrub cover (Gautheria shallon), mast producing trees (e.g., Notholithocarpus densiflorus), increased pine (Pinus sp.) proportion of total basal area, and annual precipitation, areas with low and high amounts of canopy cover and slope, and cooler August temperatures. We found little evidence that Humboldt martens were associated with old-growth structural indices. This study provides an example of how limited information on lesser-known species can lead to differing interpretations, emphasizing the need for study-level replication in ecology. Conservation efforts and assessment of risks to Humboldt marten populations would benefit from continued survey effort to clarify distribution, population sizes, and fine-scale habitat use.

Quantifying the demography of wildlife populations is imperative to evaluating population trends, but identifying mechanisms that influence demographic outcomes can be difficult for cryptic species. We radio-tracked Pacific martens (Martes caurina), an 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 confirmed as predations via clinical forensic evidence, with bobcats (Lynx rufus; n = 5) representing all clinically confirmed predations. The proximate cause of mortality for one marten was attributed to toxicosis from anticoagulant rodenticide exposure, which has not been previously reported in free-ranging martens. Further, martens appeared to be more vulnerable to predation during reproductive periods that incur increased energetic requirements (e.g., lactation, kit-rearing, mating). We propose continued pairing of field and clinical assessments to better substantiate causes of mortality, elucidate pathology, and identify novel stressors.

The fisher is a forest-dwelling carnivore of conservation concern in the southern Sierra Nevada. In recent years, drought followed by extensive tree mortality has dramatically altered the forest in this region. Between 2007 and 2018, we located fisher scat using detection dog teams twice a year in a standardized grid, providing information on fisher space and habitat use prior to and during these climate-induced disturbance events. We found that fisher space-use was positively correlated with live forest prior to the drought, and live forest was strongly associated with areas where fishers persisted during and after disturbance. Fishers persisted in areas with tree mortality if they were already present, but they were unlikely to colonize new areas with tree mortality. The presence of California black oak had a positive influence on space-use at the start of the study and was positively associated with areas where fishers persisted and colonized over time. Fishers were less likely to occur in areas farther from streams. Overall, the proportion of the study area used by fishers declined over time. Our results highlight the value of live forest stands and California black oaks on the landscape if fishers are to persist in this region.

In the past few years, myself and colleagues have published over a dozen papers on Pacific marten survey techniques, ecology, movement, survival, energetics, reproduction, habitat use, and tradeoffs for long-term monitoring. Within this presentation, I provide a brief overview of marten ecology - combining new information with common paradigms. My goal is to provide the audience with a general background that will allow for deeper appreciation and understanding of a forest-dependent species of conservation concern. I highlight recent research on Humboldt or coastal martens, which are Endangered in California and federally Threatened. For managers and researchers alike, I conclude with opportunities to collect more comprehensive data using traditional methods (e.g., remote cameras) and considerations for combining data.