Dataset Information

Density and population viability of coastal marten: a rare and geographically isolated small carnivore.

ABSTRACT: Pacific martens (Martes caurina humboldtensis) in coastal forests of Oregon and northern California in the United States are rare and geographically isolated, prompting a petition for listing under the Endangered Species Act. If listed, regulations have the potential to influence land-use decisions on public and private lands, but no estimates of population size, density, or viability of remnant marten populations are available for evaluating their conservation status. We used GPS and VHF telemetry and spatial mark-resight to estimate home ranges, density, and population size of Pacific martens in the Oregon Dunes National Recreation Area, central coast Oregon, USA. We then estimated population viability at differing levels of human-caused mortality (e.g., vehicle mortality). Marten home ranges were small on average (females = 0.8 km2, males 1.5 km2) and density (1.13 martens/1 km2) was the highest reported for North American populations (M. caurina, M. americana). We estimated 71 adult martens (95% CRI [41-87]) across two subpopulations separated by a large barrier (Umpqua River). Using population viability analysis, extinction risk for a subpopulation of 30 martens, approximately the size of the subpopulation south of the Umpqua River, ranged from 32% to 99% with two or three annual human-caused mortalities within 30 years. Absent population expansion, limiting human-caused mortalities will likely have the greatest conservation impact.

SUBMITTER: Linnell MA

PROVIDER: S-EPMC5889706 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Density and population viability of coastal marten: a rare and geographically isolated small carnivore.

Linnell Mark A MA Moriarty Katie K Green David S DS Levi Taal T

PeerJ 20180404

Pacific martens (<i>Martes caurina humboldtensis</i>) in coastal forests of Oregon and northern California in the United States are rare and geographically isolated, prompting a petition for listing under the Endangered Species Act. If listed, regulations have the potential to influence land-use decisions on public and private lands, but no estimates of population size, density, or viability of remnant marten populations are available for evaluating their conservation status. We used GPS and VHF ...[more]

PMID: 29637018

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Project description: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.

Project description:Forest management guidelines for rare or declining species in the Pacific Northwest, USA, include both late successional reserves and specific vegetation management criteria. However, whether current management practices for well-studied species such as northern spotted owls (Strix occidentallis caurina) can aid in conserving a lesser known subspecies-Humboldt martens (Martes caurina humboldtensis)-is unclear. To address the lack of information for martens in coastal Oregon, USA, we quantified vegetation characteristics at locations used by Humboldt martens and spotted owls in two regions (central and southern coast) and at two spatial scales (the site level summarizing extensive vegetation surveys and regionally using remotely sensed vegetation and estimated habitat models). We estimated amount of predicted habitat for both species in established reserves. If predicted overlap in established reserves was low, then we reported vegetation characteristics to inform potential locations for reserves or management opportunities. In the Central Coast, very little overlap existed in vegetation characteristics between Humboldt martens and spotted owls at either the site or regional level. Humboldt martens occurred in young forests composed of small diameter trees with few snags or downed logs. Humboldt martens were also found in areas with very dense vegetation when overstory canopy and shrub cover percentages were combined. In the South Coast, Humboldt martens occurred in forests with smaller diameter trees than spotted owl sites on average. Coastal Humboldt martens may use stands of predicted high quality spotted owl habitat in the Pacific Northwest. Nonetheless, our observations suggest that coastal Humboldt martens exist in areas that include a much higher diversity of conifer size classes as long as extensive dense shrub cover, predominantly in the form of high salal and evergreen huckleberry, are available. We suggest that managers consider how structural characteristics (e.g., downed logs, shrub cover, patch size), are associated with long-term species persistence rather than relying on reserves based on broad cover types. Describing vegetation may partially describe suitability, but available prey or predation risk ultimately influence likelihood of individual Humboldt marten use. Guidelines for diversifying vegetation management, and retaining or restoring appropriate habitat conditions at both the stand level and regionally, may increase management flexibility and identify forest conditions that support both spotted owls and Humboldt martens.

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Project description:Cougar (Puma concolor) observations have increased in Midwest North America, with breeding populations re-establishing in several regions east of their contemporary range. The Cypress Hills Uplands, located in southwest Saskatchewan and southeast Alberta, was recently re-colonized by cougars and now supports the easternmost confirmed breeding population of cougars in Canada. A number of factors contribute to this cougar range expansion, but it is dispersal that provides the mechanism for re-colonization of historic range. We used GPS-collar data to examine space-use and movement behavior of sub-adult cougars, the age class associated with dispersal, in the Cypress Hills. Conditional logistic regression and a two-stage modeling approach were used to estimate resource selection functions (RSF) of sub-adult cougars during two distinct ranging behaviors: transient movements (i.e., dispersal and exploratory forays) and localizing movements (i.e., temporary home ranges). Linear regression was used to model movement rates, measured as the distance between consecutive 3-h GPS-relocations, of sub-adult cougars relative to different habitats, times of day and between transient and localizing behavior. All individual sub-adult cougars displayed bouts of transient and localizing behavior. All male cougars dispersed from their natal ranges and travelled considerably farther distances than female cougars. One male dispersed over 750 km eastward through the agricultural belt of northern Montana and southern Saskatchewan. Males occupied temporary home ranges in more open habitats on the fringes of the insular Cypress Hills, while females appeared to be recruited into the adult population, occupying treed habitat that provided more suitable cover. During both ranging behaviors, sub-adult cougars selected for rugged terrain and proximity to hydrological features (likely supporting riparian habitats) and avoided open cover types. Differences in habitat selection between ranging behaviors were observed in response to open water, roads and elevation. Although certain habitat characteristics were preferred, transient and localizing cougars used fast-paced nocturnal movements and shortened daytime movements when traversing open habitats to effectively limit their residency and exposure in less-suitable landscapes. Additionally, cougars moved greater distances at night during transient behavior compared to localizing behavior indicating cougars used cover of darkness to traverse novel terrain. In doing so, sub-adult cougars can successfully disperse several hundred kilometres across a matrix of open habitat in search of resources and mates.

Dataset Information

Density and population viability of coastal marten: a rare and geographically isolated small carnivore.

Publications

Density and population viability of coastal marten: a rare and geographically isolated small carnivore.

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