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

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Marie Martin at Oregon State University
Marie Martin
Katie Moriarty at NCASI
Katie Moriarty
Jonathan N. Pauli
Jonathan N. Pauli
Jonathan N. Pauli
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Context 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. Objectives 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). Methods 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. Results 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. Conclusions 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.
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RESEARCH ARTICLE
Landscape seasonality influences the resource selection
of a snow-adapted forest carnivore, the Pacific marten
Marie E. Martin .Katie M. Moriarty .Jonathan N. Pauli
Received: 13 February 2020 / Accepted: 10 February 2021 / Published online: 27 February 2021
ÓThe Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature 2021
Abstract
Context 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 season-
ally snow-covered environments.
Objectives We quantified space-use and scale-de-
pendent 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).
Methods 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, topo-
graphic, 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.
Results 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.
Conclusions 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
Supplementary Information The online version of this
article (https://doi.org/10.1007/s10980-021-01215-9) contains
supplementary material, which is available to authorized users.
M. E. Martin (&)J. N. Pauli
Department of Forest and Wildlife Ecology, University of
Wisconsin-Madison, Madison, WI, USA
e-mail: marie.martin@oregonstate.edu;
martin.marie.ellen@gmail.com
M. E. Martin
Institute for Natural Resources, Oregon State University,
Portland, OR, USA
K. M. Moriarty
Pacific Northwest Research Station, United States Forest
Service, Olympia, WA, USA
K. M. Moriarty
National Council for Air and Stream Improvement, Inc.,
Corvallis, OR, USA
123
Landscape Ecol (2021) 36:1055–1069
https://doi.org/10.1007/s10980-021-01215-9(0123456789().,-volV)(0123456789().,-volV)
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Martens can exhibit habitat selection at multiple spatial scales (Slauson et al. 2007, Thompson et al. 2012. We used bivariate spatial scale optimization to identify the optimal spatial scale for each variable, which is a technique used to capture scale-dependent effects of habitat selection for martens (Shirk et al. 2014, Tweedy et al. 2019, Martin et al. 2021. We created six spatial scales represented by buffers around the 2 km grid point (station A) for each survey unit with radii of 50, 270, 500, 750, 1,170, and 3,000 m. ...
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... scales (Slauson et al. 2019, Moriarty et al. 2021) and we sought to follow these methods, it may 478 have been more appropriate to exclude the use of the smaller spatial scales (50-270-m) as these 479 did not match the scales of habitat selection we were explicitly modeling. We recommend that 480 the spatial scales used in multi-scale habitat analyses carefully evaluate scales of habitat 481 selection that the study design and dataset can address and select only spatial scales for 482 consideration that are relevant to the specific research objectives. ...
Habitat use and distribution of a recently discovered population of Humboldt martens
Preprint
Full-text available
  • Jul 2024
The Humboldt marten (Martes caurina humboldtensis) has declined from over 95 % of its historic range and currently occurs in just four extant population areas (EPAs). Prior to their listing under the Endangered Species Act, a conservation strategy was developed to identify key conservation needs for this species. This assessment identified an area near the California–Oregon (CA–OR) border as the second EPA in California, yet little was known about the overall distribution or habitat used by this population. This prompted our investigation to provide the first systematic survey of the CA–OR EPA and to assess habitat use under an occupancy modeling framework. Between 2017–2018 we surveyed 51 survey units in and around the EPA and detected martens at 20 (39.2 %). We found that occupancy was most influenced by the spatial scale-specific amount of low-elevation late-seral old-growth forest habitat, riparian habitat, and mid-seral forest habitat. Occupancy by marten was greatest in low-elevation (< 800 m) habitat and was positively associated with late-seral forest habitat at the 1,170-m home range scale (Odds Ratio [OR] = 35.31, 95 % CI = 1.30–958.07), riparian habitat at the 1,170-m home range scale (OR = 3.20, 95 % CI = 1.01–10.1), and increased amounts of mid-seral forest habitat at the 50-m microhabitat scale (OR = 1.28, 95 % CI = 0.95–1.73). Our findings identified habitat types important for explaining the distribution of this understudied population, addressing two of the highest priority research needs identified in the Humboldt marten conservation strategy.
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... Resource selection is also known to reflect a species habitat requirements that vary seasonally, forcing analyses to be conducted at the appropriate temporal scales Mayor et al. 2009). This is of utmost importance for species inhabiting temperate ecosystems with predictable seasonal shifts in resource needs and availability (Ellington et al. 2020;Martin et al. 2021). For example, Cougars (Puma concolor) in Canada selected wetlands and avoided forests in summer, while the opposite relationship was observed in winter, probably because prey change habitat seasonally (Smereka et al. 2020). ...
Seasonal shifts in the habitat selection patterns of male American Marten ( Martes americana ) at a fine spatial scale
Article
  • May 2024
Old-growth forests harbor a large amount of complex structural features that result in a wide array of wildlife habitats. However, intensive forest management is gradually converting old-growth forest into younger, even-aged stands, reducing structural complexity and threatening the persistence of old-growth-dependent species. Maintaining elements of complex stand structure is critical to the conservation of old-growth forest specialists that use different habitat components at different periods of their annual cycle, and it requires a comprehensive understanding of seasonal variation in the habitat needs of these species. However, difficulties in observing free-ranging animals have sometimes limited our ability to assess such variations in habitat requirements, especially for small, elusive species. To address this, we used GPS telemetry collars to describe fine-scale habitat selection patterns of 6 male American Martens (Martes americana) during 2 contrasting periods of the year (snow-free, from mid-April to mid-November; snow-covered, from mid-November to mid-April), an objective formerly hard to achieve using conventional VHF telemetry. We used resource selection functions conducted at the fourth order of selection to compare habitat characteristics found at the sites used by martens (GPS locations, n = 100) to those found on an equal number of available sites (random points, n = 100) within each individual seasonal home range. We conducted vegetation surveys on these 200 sites to describe habitat and built candidate models representing different concurrent hypotheses. Our results showed that proxies of prey availability, predator avoidance, and thermal constraints were the primary factors influencing marten habitat selection during both periods, although their respective importance differed between periods. Martens selected sites with a high density of large-diameter snags (≥30·ha−1), high conifer canopy closure (≥53%), and a dense lateral cover (≥81%) during the snow-free period, but selected sites with a high volume of coarse woody debris (≥64 m3·ha−1) and high conifer canopy closure (≥48%) during the snow-covered period. Our results highlight the importance of contrasting seasonal changes in habitat selection patterns of small carnivores and may help maintain structural attributes in the landscape that are suitable for male American Martens.
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... For example, RSFs have been used to identify broad conservation corridors (Chetkiewicz & Boyce, 2009) and high wildlife density areas to improve rabies vaccination programs (McClure et al., 2022). Additionally, RSFs have been used to understand how habitat selection is affected by seasons (Martin et al., 2021) anthropogenic developments (Knopff et al., 2014), and the presence of predators (Florko et al., 2023), and can be used to understand the cumulative effects of such factors (Darlington et al., 2022). ...
A review of statistical models used to characterize species-habitat associations with animal movement data
Preprint
Full-text available
  • Jan 2024
1. Understanding species-habitat associations is fundamental to ecological sciences and for species conservation. Consequently, various statistical approaches have been designed to infer species-habitat associations. Due to their conceptual and mathematical differences, these methods can yield contrasting results. 2. In this paper, we describe and compare commonly used statistical models that relate animal movement data to environmental data. Specifically, we examined selection functions which include resource selection function [RSF] and step-selection function [SSF], as well as hidden Markov models (HMMs) and related methods such as state-space models. We demonstrate differences in assumptions of each method while highlighting advantages and limitations. Additionally, we provide guidance on selecting the most appropriate statistical method based on research objectives and intended inference. To illustrate the varying ecological insights derived from each statistical model, we apply them to the movement track of a single ringed seal (Pusa hispida) in a case study. 3. Through our case study, we demonstrate that each model yields varying ecological insights. For example, the RSF indicated selection of areas with high prey diversity, whereas the SSFs indicated no discernable relationship with prey diversity. Furthermore, the HMM reveals variable associations with prey diversity across different behaviors, for example, a positive relationship between prey diversity and a slow-movement behaviour. Notably, the three models identified different “important” areas. 4. This case study highlights the critical significance of selecting the appropriate model as an essential step in the process of identifying species-habitat relationships and specific areas of importance. Our comprehensive review provides the foundational information required for making informed decisions when choosing the most suitable statistical methods to address specific questions, such as identifying expansive corridors or protected zones, understanding movement patterns, or studying behaviours. In addition, this study informs researchers with the necessary tools to apply these methods most effectively.
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... The approach employed in this study may be valuable for species like Tasmanian devils (Sarcophilus harrisii) and Eastern Quolls (Dasyurus viverrinus) in Australia, which also face high levels of roadkill in Tasmania (Jones 2000). The approach can also be applied to other species, such as the Florida panther (Puma concolor coryi) and Pacific marten (Martes caurina), which are particularly sensitive to human impacts on their habitat, including landscape-scale effects of habitat loss and fragmentation (Kautz et al. 2006;Martin et al. 2021). Based on this study, further research should be undertaken to better understand the causes and consequences of individual movement and space-use behaviour (i.e. ...
Habitat, connectivity, and roadkill of Korea’s apex predator, the yellow-throated marten
Article
Full-text available
  • Jul 2023
Context The yellow-throated marten (Martes flavigula), an endangered species in South Korea, is an important apex predator of that country’s temperate forest ecosystem. Human impacts on the landscape continue to threaten marten populations, for which there is insufficient understanding of critical habitats and areas required for population connectivity. Aims In this study, our aim was to develop models of habitat suitability and connectivity networks for the yellow-throated marten to inform comprehensive landscape conservation strategies. Methods We used an ensemble of five species distribution models (boosted regression trees, BRT; generalised linear model, GLM; multivariate adaptive regression spline, MARS, maximum entropy model, MaxEnt; and random forest, RF) to identify the main environmental factors influencing marten distribution and potential suitable habitats. We employed a network-based landscape lattice approach combined with circuit theory to predict the potential habitat linkages of martens, and we examined their relevance to marten roadkill. Key results Five species distribution models performed well with a range of test area under the curve (AUC) values from 0.809 to 0.826 (mean = 0.820) with true skill statistic values over 0.5. Elevation and the amount of vegetation cover were the first and second-most important factors for occurrence probability, and they generally exerted positive influences. Distances from human settlements and roads were also positively related to occurrence probability. We determined appropriate spatial resolutions for conserving functional habitat linkages, which are related to its roadkill distribution, and identified the distribution pattern of key linkage areas. Conclusions We effectively identified the potential distribution of marten habitats and linkages between them at regional and functional levels to maintain ecological processes. Implications The results and approaches presented here could be useful in understanding and delineating priority habitats and linkage areas for species conservation and landscape management.
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... Differentiation in habitat use can serve to foster co-existence, however evidence found here suggests that, at carrion sites, mustelid interactions could intensify by breaking down habitat niche partitioning. Snow depth can further influence movements and incur metabolic costs to mustelids, which can negate gains made from foraging at carcasses [80][81][82] . Martens are highly adapted to mobility over deep snow 83 though under conditions of high snow accumulation, they also use subnivean cavities as rest sites to reduce heat loss 23 . ...
Influence of heterospecifics on mesocarnivore behaviour at shared scavenging opportunities in the Canadian Rocky Mountains
Article
Full-text available
  • Jul 2023
In seasonal environments, the ability of mustelid species to acquire carrion—a dietary resource heavily depended upon—is driven by a collection local habitat characteristics and competition dynamics. In resource-scarce winter, sympatric mesocarnivores must balance energetic rewards of carrion with avoiding antagonistic interactions with conspecifics. We examined scavenging interactions among three mustelid species in the northern Canadian Rocky Mountains. Camera traps (n = 59) were baited with carrion during winter between 2006 to 2008. Spatial and temporal dimensions of scavenger behaviour (i.e., carcass use) were evaluated using a multi-model approach, which enabled us to recognize potentially adaptive behavioural mechanisms for mitigating competition at carcass sites. Best performing models indicated that carrion site use is governed by a combination of competition threats and environmental factors. A decrease in scavenging with increasing snow depth was observed across all species. Mustelids adopted a host of adaptive behavioural strategies to access shared scavenging opportunities. We found evidence that wolverine (Gulo gulo) and American marten (Martes americana) segregate in space but temporally tracked one another. Short-tailed weasel (Mustela erminea) scavenging decreased with greater site use by marten. Carcass availability across a spatially complex environment, as well as spatial–temporal avoidance strategies, can facilitate carrion resource partitioning.
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... Snow simultaneously limits the presence of larger carnivores that lack similar morphological adaptations (Martin et al. 2021, Smith et al. 2022b) while also facilitating improved hunting efficiency of martens during an energetically demanding time of year (Buskirk and Harlow 1989, Gilbert et al. 2009, Martin et al. 2020. Given the prevalence of shrubs and absence of snow in regions where Humboldt martens occur, we posit that shrub cover serves proxy functions for snow in areas where snow cover is inconsistent or not present. ...
Structural complexity characterizes fine‐scale forest conditions used by Pacific martens
Article
Full-text available
  • Mar 2023
When 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.
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... Based on our results, martens do not appear to be impacted by variation in snow depth, at least within the sampling frame of our camera traps. Snow does not seem to limit marten habitat use (Raine, 1983;Martin et al., 2021), and indeed marten may take advantage of deeper snow to avoid predators (e.g., bobcats [L. rufus] and coyotes; Krohn et al., 2005;Moriarty et al., 2015). ...
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Western spotted skunk spatial ecology in the temperate rainforests of the Pacific Northwest
Article
Full-text available
  • Aug 2024
A major threat to small mammalian carnivore populations is human‐induced land use change, but conservation and management are inhibited by limited knowledge about their ecology and natural history. To fill a key knowledge gap of the western spotted skunk (Spilogale gracilis), we investigated their spatial ecology at the landscape and home range scale in the temperate rainforests of the Oregon Cascades during 2017–2019. For the landscape scale analysis, we used detections of western spotted skunks at 112 baited camera traps and fitted a dynamic occupancy model to investigate spatial distribution and drivers of inter‐seasonal and inter‐annual changes in occupancy. Concurrently, we radio‐collared 25 spotted skunks (9 female, 16 male) and collected 1583 relocations. Using continuous‐time movement models, we estimated large home range sizes for both male and female spotted skunks, relative to their body mass, and highly overlapping home ranges that indicated a lack of territoriality. Using these home ranges, we fitted a resource selection function using environmental covariates that we assigned to various hypotheses such as resources, predator avoidance, thermal tolerance, and disturbance. Overall, western spotted skunks were widely distributed across our study area (seasonal occupancy up to 63.7 ± 5.3%) and highly detectable (weekly detection probability = 41.2%). At both spatial scales, spotted skunks selected wetter areas and local valleys, which we attributed to areas with more food resources. At the home range scale, spotted skunks selected locations with lower predation risk and areas surrounded by more previously logged forests. In this montane environment, inter‐seasonal contractions in the spatial distributions of spotted skunks were strongly driven by their response to cold temperature and accumulated snow. This was especially evident when seasonal occupancy declined significantly following a severe heavy snow event in February 2019. Given that there is little information available on the natural history of the western spotted skunk, these results provide essential information about their ecology to focus future monitoring efforts and may help identify potential threats (e.g., forest management, severe snow events, or wildfires) to this species.
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Comparative Reproductive Ecology of Two Subspecies of Pacific Marten (Martes caurina) in California
Article
Full-text available
  • May 2021
  • NORTHWEST SCI
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.
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Habitat selection patterns are density dependent under the ideal free distribution
Article
Full-text available
Despite being widely used, habitat selection models are rarely reliable and informative when applied across different ecosystems or over time. One possible explanation is that habitat selection is context‐dependent due to variation in consumer density and/or resource availability. The goal of this paper is to provide a general theoretical perspective on the contributory mechanisms of consumer and resource density‐dependent habitat selection, as well as on our capacity to account for their effects. Towards this goal we revisit the ideal free distribution (IFD), where consumers are assumed to be omniscient, equally competitive and freely moving, and are hence expected to instantaneously distribute themselves across a heterogeneous landscape such that fitness is equalised across the population. Although these assumptions are clearly unrealistic to some degree, the simplicity of the structure in IFD provides a useful theoretical vantage point to help clarify our understanding of more complex spatial processes. Of equal importance, IFD assumptions are compatible with the assumptions underlying common habitat selection models. Here we show how a fitness‐maximising space use model, based on IFD, gives rise to resource and consumer density‐dependent shifts in consumer distribution, providing a mechanistic explanation for the context‐dependent outcomes often reported in habitat selection analysis. Our model suggests that adaptive shifts in consumer distribution patterns would be expected to lead to nonlinear and often non‐monotonic patterns of habitat selection. These results indicate that even under the simplest of assumptions about adaptive organismal behaviour, habitat selection strength should critically depend on system‐wide characteristics. Clarifying the impact of adaptive behavioural responses may be pivotal in making meaningful ecological inferences about observed patterns of habitat selection and allow reliable transferability of habitat selection predictions across time and space.
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Can landscape heterogeneity promote carnivore coexistence in human-dominated landscapes?
Article
Full-text available
  • Sep 2020
  • LANDSCAPE ECOL
ContextInterspecific competition can limit species distributions unless competitors partition niche space to enable coexistence. Landscape heterogeneity can facilitate niche partitioning and enable coexistence, but land-use change is restructuring terrestrial ecosystems globally with unknown consequences for species interactions.Objectives We tested the relationship between landscape heterogeneity and carnivore co-occurrence in natural and human-dominated ecosystems to assess the landscape-mediated impacts of anthropogenic change on coexistence.Methods We used boosted regression trees to model the distributions and co-occurrence of two competing forest carnivores, American martens and fishers, at two contrasting sites in the Great Lakes region, USA: a “natural” site largely devoid of human impacts and a “human-dominated” site with substantial development and a history of land-use change. We assessed the importance of climate and habitat variables for each species, measured spatial niche overlap, and quantified co-occurrence as a function of compositional (patch richness), configurational (landscape shape), and topographical (elevation range) heterogeneity per site.ResultsWe observed significant differences in the effect of heterogeneity on co-occurrence between sites. The natural landscape exhibited little niche overlap and co-occurrence had a significant, positive relationship with heterogeneity. Conversely, the human-dominated site exhibited high niche overlap with variable effects of heterogeneity on co-occurrence. Elevation, snowpack, and development had strong, contrasting effects on marten and fisher distributions, suggesting that differential use of habitat and anthropogenic features facilitates coexistence.Conclusions Heterogeneity can facilitate coexistence, but too much may undermine carnivore coexistence in human-dominated landscapes where habitat and space are limited. Moreover, future climate change will likely erode niche partitioning among martens and fishers, with particularly strong consequences for coexistence in human-dominated landscapes and at range boundaries.
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Temperature shapes movement and habitat selection by a heat-sensitive ungulate
Article
Full-text available
  • Sep 2020
  • LANDSCAPE ECOL
ContextWarmer weather caused by climate change poses increasingly serious threats to the persistence of many species, but animals can modify behavior to mitigate at least some of the threats posed by warmer temperatures. Identifying and characterizing how animals modify behavior to avoid the negative consequences of acute heat will be crucial for understanding how animals will respond to warmer temperatures in the future.Objectives We studied the extent to which moose (Alces alces), a species known to be sensitive to heat, mitigates heat on hot summer days via multiple different behaviors: (1) reduced movement, (2) increased visitation to shade, (3) increased visitation to water, or (4) a combination of these behaviors.Methods We used GPS telemetry and a step-selection function to analyze movement and habitat selection by moose in northeastern Minnesota, USA.ResultsMoose reduced movement, used areas of the landscape with more shade, and traveled nearer to mixed forests and bogs during periods of heat. Moose used shade far more than water to ameliorate heat, and the most pronounced changes in behavior occurred between 15 and 20 °C.Conclusions Research characterizing the behaviors animals use to facilitate thermoregulation will aid conservation of heat-sensitive species in a warming world. The modeling framework presented in this study is a promising method for evaluating the influence of temperature on movement and habitat selection.
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Forest structure and snow depth alter the movement patterns and subsequent expenditures of a forest carnivore, the Pacific marten
Article
Full-text available
  • Nov 2019
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 (<5kg) 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 on 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. This article is protected by copyright. All rights reserved.
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Resource selection of mule deer in a shrub‐steppe ecosystem: influence of woodland distribution and animal behavior
Article
Full-text available
  • Nov 2019
Ungulates inhabiting arid ecosystems are reliant on productive forb and shrub communities during summer months to meet nutritional demands for survival and reproduction. In the western United States, expansion of woodland vegetation into shrub‐dominated communities and the potential loss of habitat are of concern with regard to animal populations reliant on robust sagebrush shrub and forb vegetation. We used mixed‐effects logistic regression to model resource selection of female mule deer (Odocoileus hemionus) during the summers of 2005–2008. We considered selection at two spatial scales, and during three daily activity periods (night, crepuscular, and mid‐day) corresponding to resting and foraging. We evaluated habitat variables related to vegetation type, site productivity, terrain attributes, and fine‐scale abundance of pinyon–juniper cover. Those attributes allowed us to account for variation in site productivity and animal behaviors that could obscure the true relationship between density of pinyon–juniper woodland and habitat use by mule deer. We detected observable differences in habitat use by mule deer among the three activity periods with significant differences in movement rates. Deer were most active during crepuscular periods corresponding with foraging activity, and least active mid‐day when temperatures were highest. Summer habitat consisted of sites with high potential productivity, greater shrub abundance, and greater proximity to riparian areas. Deer avoided high levels of tree cover (>40% coverage) at all spatial and temporal scales, and in general selection declined with increasing pinyon–juniper cover, particularly during foraging periods. Nonetheless, mule deer selected areas with low to intermediate tree cover (10% to 40%) during resting periods and avoided areas of productive shrub and forb vegetation and riparian areas, when surrounded by denser stands of pinyon–juniper cover. These results emphasize the importance of productive shrub and forb vegetation to mule deer inhabiting semi‐arid regions and suggest that low levels of tree cover are beneficial, especially during resting periods. Nevertheless, dense pinyon–juniper cover was generally avoided even in areas of high site productivity. These relationships lend support to the concern that increases in large, dense stands of pinyon–juniper reduce availability of summer habitat and alter patterns of resource selection for mule deer, a shrub‐dependent ungulate.
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Resource use by marten at fine spatial extents
Article
  • Aug 2020
Martens (Martes spp.) occupy areas with complex forest structure that can exhibit patchy distribution, particularly in managed forest landscapes. These structures (e.g., downed wood) are often difficult to reliably sample so more easily acquired surrogates may better describe marten habitat. Recent advances in global positioning system (GPS) collars combined with integrated (i.e., imagery with geospatial modeling), resolute, remotely sensed maps offer a potentially efficient means of understanding marten space use. We placed GPS collars on 13 American marten (M. americana), attempted to acquire a locational fix every 15 min, and calculated adaptive kernel home ranges from successful locations. We modeled probability of marten use as a function of covariates derived from remotely sensed data that included proportion of vegetation cover types, and distances to maintained roads and hydrographic features at 2.5, 4.5, and 7.1 ha extents. Average cover type values varied minimally across spatial extents we evaluated, indicating fine-scale homogenization. Amount of tall (> 10 m) deciduous forest, tall and short conifer forests, and riparian forests had positive effects on marten use, whereas distance to maintained roads had a weak negative effect. Broad riparian areas (e.g., scrub–shrub swamps that occur in broad topographic depressions), not necessarily associated with mapped hydrographic lines, were heavily used by marten. We found that core use areas for marten could reliably be predicted from 30 m remotely sensed maps summarized at relatively small extents (2.4–7.1 ha).
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Wave-like Patterns of Plant Phenology Determine Ungulate Movement Tactics
Article
  • Jul 2020
  • CURR BIOL
Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called “green-wave surfing” [3, 4, 5]. Yet general principles describing how the dynamic nature of resources determine movement tactics are lacking [6]. We tested an emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of green-up facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change [10], our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.
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Identifying conservation priority areas for the Andean condor in southern South America
Article
  • Mar 2020
  • BIOL CONSERV
Mobile species face an array of human threats across political boundaries, and their protection relies on identifying and prioritizing areas for conservation. Large avian scavengers are one of the widest ranging and most threatened species globally, and efforts to preserve them have come to the forefront of wildlife management. Vultures require access to functionally distinct habitats for roosting, foraging and flying, yet behavior-specific habitat modelling has been overlooked in management planning. Herein, we developed a spatial prioritization model for the threatened Andean condor (Vultur gryphus) that integrates activity-specific habitat selection across heterogeneous landscapes. We tracked 35 individuals in two regions of Argentina and Chile differing in topography and vegetation composition, and analyzed how landscape covariates influence where condors roost, forage and fly, while accounting for individual differences. We found that individuals responded differently to environmental covariates during each behavior, and identified regional differences for some covariates dependent on behavioral state. We also found important individual differences in habitat selection between birds inhabiting each region. We combined these results into an ensemble spatial prioritization model, and found that most areas of high priority for Andean condor conservation are not under protection. The strategic implementation of conservation measures in these priority areas could have important implications for the recovery of this species. Our study illustrates the value of integrating behavioral- and individual-specific habitat analyses into spatial conservation planning, and points to opportunities for effective management of threatened vultures.
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