Movement Corridors Research Articles

Population connectivity and genetic diversity of American marten (Martes americana) in the United States northern Rocky Mountains in a climate change context

Climate change is likely to alter population connectivity, particularly for species associated with higher elevation environments. The goal of this study is to predict the potential effects of future climate change on population connectivity and genetic diversity of American marten populations across a 30.2 million hectare region of the in the US northern Rocky Mountains. We use a landscape resistance model validated from empirical landscape genetics modeling to predict the current and expected future extent and fragmentation of American marten dis- persal habitat under five climate change scenarios, corre- sponding to climatic warming of between 0.7 and 3.3 C, consistent with expected climate change by year 2080. We predict the regions of the current and future landscapes where gene flow is expected to be governed by isolation by distance and the regions where population fragmentation is expected to limit gene flow. Finally, we predict changes in the strength and location of predicted movement corridors, fracture zones and the location of dispersal barriers across the study area in each scenario. We found that under the current climate, gene flow is predicted to be limited primarily by distance (isolation), and landscape structure does not significantly limit gene flow, resulting in very high genetic diversity over most of the study area. Projected climatic warming substantially reduces the extent and increases the fragmentation of marten populations in the western and northwestern parts of the study area. In con- trast, climate change is not predicted to fragment the extensive higher elevation mountain massifs in central Idaho, the northern U.S. continental divide, and Greater Yellowstone Ecosystem. In addition, we show locations in the study area that are important corridors in the current landscape that remain intact across the climate change scenarios.

Management and Conservation of San Joaquin Kit Foxes in Urban Environments

Author(s): Cypher, Brian L.; Van Horn Job, Christine L. | Abstract: The San Joaquin kit fox is listed as federally Endangered and California Threatened, primarily due to habitat loss from agricultural, industrial, and urban developments. However, a population of kit foxes estimated at 200-400 persists within the city of Bakersfield, CA. This population appears to be demographically robust with a high probability of persistence. Thus, this population potentially could contribute to range-wide conservation and recovery efforts. The presence of this population in an urban environment creates management challenges. Management issues include human and pet safety, dens in inconvenient locations, and carcass disposal. Resolution of these issues generally is not difficult. Conservation challenges include roads and vehicles, rodenticides and other toxins, sports netting, den destruction during routine maintenance operations, interspecific competition and disease transmission, movement corridors, and regulatory policy. Although the Metropolitan Bakersfield Habitat Conservation Plan provides protective measures for kit foxes during new construction, such measures do not extend to operations, maintenance, and other routine activities. Furthermore, formal policies regarding management and conservation of urban kit foxes have not yet been developed by the U.S. Fish and Wildlife Service and California Department of Fish and Game, resulting in inconsistent responses to urban kit fox issues. Based on a public opinion survey, Bakersfield residents generally support conservation of urban kit foxes. Successful resolution of management issues will minimize conflicts and enhance efforts to conserve kit foxes.

UNICOR: a species connectivity and corridor network simulator

We introduce UNIversal CORridor network simulator (UNICOR), a species connectivity and corridor identification tool. UNICOR applies Dijkstra's shortest path algorithm to individual‐based simulations. Outputs can be used to designate movement corridors, identify isolated populations, and prioritize conservation plans to promote species persistence. The key features include a driver‐module framework, connectivity mapping with thresholding and buffering, and calculation of graph theory metrics. Through parallel‐processing, computational efficiency is greatly improved, allowing analyses of large extents and entire populations. Previously available approaches are limited by prolonged computational times and poor algorithmic efficiency, restricting problem‐size and requiring artificial subsampling of populations.

Movement responses by wolves to industrial linear features and their effect on woodland caribou in northeastern Alberta

Woodland caribou (Rangifer tarandus caribou) populations are declining across most of their range. Predation by wolves (Canis lupus) is believed to be the main proximate cause of these declines. However, it has been hypothesized that recent forestry and energy sector activity in caribou range ultimately might have caused population declines by altering wolf-caribou relationships. We tested the hypothesis that industrial linear features influence wolf movements in woodland caribou range in northeastern Alberta, resulting in increased wolf-caused caribou mortalities close to these features. Using step selection functions (SSF) and observed vs. simulated wolf movement paths, we found that wolf movement was influenced by natural linear features (rivers and streams) throughout the year, possibly because they provide ease of travel and high prey abundance. Wolf movement was further influenced by industrial linear features, but use of these features differed depending on line- type and season. Wolves showed strong selection for steps closer to conventional seismic lines during the snow-free season. Likewise, observed wolf movement paths followed conventional seismic lines more closely than simulated paths during snow-free months. Use of seismic lines as movement corridors might result in wolves hunting in caribou-preferred habitats (bogs and fens) more frequently than they did historically, particularly in the snow-free season when most caribou mortalities occur. However, we found no evidence that caribou mortalities occurred closer to industrial linear features than did live caribou. We conclude that wolf use of seismic lines increases predation risk for caribou close to these features, resulting in caribou avoidance of linear developments and thus functional loss of otherwise suitable habitat for caribou.

Habitat suitability modelling for species at risk is sensitive to algorithm and scale: A case study of Blanding's turtle, Emydoidea blandingii, in Ontario, Canada

Species distribution modelling (SDM) can help conservation by providing information on the ecological requirements of species at risk. We developed habitat suitability models at multiple spatial scales for a threatened freshwater turtle, Emydoidea blandingii, in Ontario as a case study. We also explored the effect of background data selection and modelling algorithm selection on habitat suitability predictions. We used sighting records, high-resolution land cover data (25m), and two SDM techniques: boosted regression trees; and maximum entropy modelling. The area under the receiver characteristic operating curve (AUC) for habitat suitability models tested on independent data ranged from 0.878 to 0.912 when using random background and from 0.727 to 0.741 with target-group background. E. blandingii habitat suitability was best predicted by air temperature, wetland area, open water area, road density, and cropland area. Habitat suitability increased with increasing air temperature and wetland area, and decreased with increasing cropland area. Low road density and open water increased habitat suitability, while high levels of either variable decreased habitat suitability. Robust habitat suitability maps for species at risk require using a multi-scale and multi-algorithm approach. If well used, SDM can offer insight on the habitat requirements of species at risk and help guide the development of management plans. Our results suggest that E. blandingii management plans should promote the protection of terrestrial habitat surrounding residential wetlands, halt the building of roads within and adjacent to currently occupied habitat, and identify movement corridors for isolated populations.

Effects of management options on mammal richness in a Mediterranean agro-silvo-pastoral system

Non-flying mammal richness and distribution were studied in a landscape matrix consisting of a highly managed agro-silvo-pastoral system dominated by a cork oak woodland (montado) to test the predictions of the Intermediate Disturbance Hypothesis (IDH). Sampling consisted on detection of mammalian signs of presence, along with the use of scent stations and small mammal live-trapping. Results were analyzed using generalized linear models, considering land uses, landscape metrics and grazing intensity and gave support to the predictions of the IDH. Pure forestry and intensive agricultural uses showed lower species richness than the silvopastoral system, whilst landscape heterogeneity and riparian corridors were shown to be most beneficial to mammal species richness, with small mammals being directly and negatively affected by grazing intensity. The increasing use of the montado for raising cattle has led to landscape homogenization by means of grazing and shrub clearance for pasture cultivation and this, combined with incremented stocking rates, constrains species richness. In this landscape context, watercourses assume a relevant role as patches of suitable habitat providing shelter, food, movement corridors and dispersion routes for mammals. Recent options of fencing forest patches with good forest natural regeneration or with a high diversity/density of Mediterranean maquis, and restoring degraded watercourses, both to improve landscape heterogeneity, appear to positively affect the mammal community. This is a current challenge in terms of monitoring and research.

Factors affecting mammalian carnivore use of riparian ecosystems in Mediterranean climates

Riparian ecosystems serve as movement and dispersal corridors; however, the factors that determine their use by multiple species of carnivores remain unknown. Two hypotheses can explain carnivore presence in riparian ecosystems. Higher riparian plant richness, diversity, and structure provide the resources used by carnivores (resting sites, cover, and food). Alternatively, areas with higher water availability allow species to withstand water loss and thermal gradients in the high summer temperatures. In southern Portugal we surveyed 70 transects 2 km long along riparian ecosystems during the wet winter months and again in the dry summer months, recording signs of carnivore species and the environmental context in which they occurred (vegetation descriptors, surrounding landscape, and waterway type and condition). Five carnivore species used riparian ecosystems (stone marten [Martes foina], Eurasian badger [Meles meles], common genet [Genetta genetta], Egyptian mongoose [Herpestes ichneumon], and red fox [Vulpes vulpes]). Riparian ecosystems had a diverse and heterogeneous plant community with a mix of obligate riparian, Mediterranean sclerophyllous, and exotic species. Most carnivore species responded to water channel type and standing water availability in both seasons, except for the stone marten in the wet season, which uses areas with rich riparian vegetation. Our results suggest that the use of riparian ecosystems is linked to water availability that provides water, prey, and external temperature regulation.

Using movement and habitat corridors to improve the connectivity for heathland carabid beetles

Heathland areas in the Netherlands are declining in size and quality, and becoming more fragmented. The connectivity of the landscape for threatened insects might be improved by creating networks of corridors. We compared heathy roadside verges and linear forest clearings with heathland nature reserves and forests. The clearings were created in between the roadside verges and the nature reserves. In all four landscape types carabid beetles were inventoried with pitfall and window traps. Principal Component Analyses showed that the carabid species composition in roadside verges differed from that in nature reserves, both before and after the creation of the connecting forest clearings. However, an analysis of data on 31 target species (stenotopic species of drift sand, heathland and other nutrient-poor open habitats) selected from the pitfall trap catches revealed that 21 were present in the roadside verges. In addition, the occurrence of teneral individuals and flightless species indicate the verges provide valuable habitat where reproduction takes place. Forests themselves were barriers for almost all target carabids. In the forest clearings, similar amounts of target carabids were encountered in pitfall traps as in the nature reserves and roadside verges, but only teneral individuals of two species were found. In contrast, flying carabids were very abundant in the forest clearings: more than twice as many as in the nature reserves and the roadside verges. This indicates that dispersing carabids in particular make use of these linear forest clearings. We conclude that roadside verges can act as habitat corridors and that linear forest clearings are particularly used as movement corridors. Thus, both offer simple solutions for increasing the connectivity of fragmented landscapes for a threatened insect group.

Modeling connectivity of black bears in a desert sky island archipelago

Landscape features such as rivers, mountains, desert basins, roads, and impermeable man-made structures may influence dispersal and gene flow among populations, thereby creating spatial structure across the landscape. In the US–Mexico borderland, urbanization and construction of the border fence have the potential to increase genetic subdivision and vulnerability to isolation in large mammal populations by bisecting movement corridors that have enabled dispersal between adjacent Sky Island mountain ranges. We examined genetic variation in black bears (Ursus americanus) from three regions in central and southern Arizona, US, to assess genetic and landscape connectivity in the US–Mexico border Sky Islands. We found that the three regions grouped into two subpopulations: the east-central subpopulation comprised of individuals sampled in the central highland and high desert regions, and the border subpopulation comprised of individuals sampled in the southern Sky Islands. Occupancy for the border subpopulation of black bears was influenced by cover type and distance to water, and occupancy-based corridor models identified 14 potential corridors connecting border Sky Island habitat cores with the east-central subpopulation. Biological quality of corridors, defined as length:width ratio and proportions of suitable habitat within corridors, declined with Sky Island dispersion. Our results show that black bears in the border subpopulation are moderately isolated from the east-central subpopulation, the main population segment of black bears in Arizona, and that connectivity for border bears may be vulnerable to anthropogenic activities, such as those associated with urbanization and trans-border security.

Relationship between landscape connectivity and gene flow for boreal caribou: clues for conservation

In order to ensure the protection of long-ranging species, the composition and configuration of a landscape which determine landscape connectivity or the degree to which the landscape facilitates or impedes the movement of organisms must be assessed. Landscape connectivity influences the species' ability to access habitat, avoid predators, move between core parts of a range and between ranges and contribute to gene flow. Knowing that different species experience landscape in scale-dependent ways and that a given landscape might appear connected to some species while fragmented to others, we used telemetry, habitat and genetic data from different caribou ranges in Manitoba and Saskatchewan to assess the importance of landscape connectivity and identify movement thresholds at different spatial scales; telemetry data for the seasonal and home range scales and genetic data for the landscape or meta-population scale. Using these thresholds, it is then possible to identify biologically relevant clusters of habitat, as these areas most contribute to overall landscape connectivity. For management purposes, the identification of these clusters may point to targeted restoration efforts in proximity of small clusters to increase the size of these core areas or the protection of movement corridors to ensure linkages between these core areas. In cases where movement between clusters is limited, each area may correspond to different ecological units or ranges that can then be analyzed or managed separately. These spatial analyses and results offer additional tools to land use and recovery planners, to support the establishment and management of protected areas. They spatially represent the composition and distribution of core habitat areas and as importantly, corridors allowing for movement and gene flow on these vast landscapes.

Matrix-dependent corridor effectiveness and the abundance of forest birds in fragmented landscapes

Corridor function for wildlife movement constitutes an important and desirable ecological characteristic of linear landscape structures. Changes in the matrix conditions, however, may result in substantial changes in the mechanisms responsible for the use of corridors by animals. I developed a model that describes the influence of matrix quality on the effectiveness of corridors for wildlife movement and the abundance of animals in the corridors. The model predicts that corridor effectiveness is maximized at intermediate matrix quality levels, while the abundance in the corridor increases asymptotically with matrix quality. I tested predictions of this model by comparing the expected and observed relative abundance of forest bird species in two landscape types of southern Chile. In nine out of 12 cases the model correctly predicted the relative abundance of forest birds. Riparian forest strips were expected to be effective functioning as corridors for five out of six studied species, although corridor effectiveness for each species varied between landscape types. A reasonable strategy to improve connectivity is to maintain (or to increase, if necessary) the matrix quality at a level such that corridors can function efficiently as both drift fences and movement conduits.

Ecology of Invasive Melilotus albus on Alaskan Glacial River Floodplains

Melilotus albus (white sweetclover) has invaded Alaskan glacial river floodplains. We measured cover and density of plant species and environmental variables along transects perpendicular to the Nenana, Matanuska, and Stikine Rivers to study interactions between M. albus and other plant species and to characterize the environment where it establishes. Melilotus albus was a pioneer species on recently disturbed sites and did not persist into closed canopy forests. The relationships between M. albus cover and density and other species were site-specific. Melilotus albus was negatively correlated with native species Elaeagnus commutata at the Nenana River, but not at the Matanuska River. Melilotus albus was positively correlated with the exotic species Crepis tectorum and Taraxacum officinale at the Matanuska River and T. officinale on the upper Stikine River. However, the high density of M. albus at a lower Stikine River site was negatively correlated with T. officinale and several native species including Lathyrus japonicus var. maritimus and Salix alaxensis. Glacial river floodplains in Alaska are highly disturbed and are corridors for exotic plant species movement. Melilotus albus at moderate to low densities may facilitate establishment of exotic species, but at high densities can reduce the cover and density of both exotic and native species.

Managing pond-breeding anurans in the selectively harvested forests of coastal New South Wales, Australia

Protective prescriptions are used to protect populations of anurans from the impacts of logging present in areas of eucalypt forestry operations in coastal New South Wales, retaining areas of undisturbed habitat known or perceived to be of importance to their survival. Current evidence indicates that the protective buffer zones applied around bodies of water are likely to provide significant protection to breeding individuals and the aquatic breeding environments. Studies of the activity patterns of anurans, however, suggest that non-breeding individuals often use forest areas falling outside of these buffers. The habitats used when not breeding are afforded some protection through the retention of habitat trees, identified suitable habitat areas and movement corridors, but significant areas can still be disturbed, and often severely, by logging machinery. Australian anuran populations appear to generally be robust to the effects of logging, with only habitat specialists showing obvious declines. I postulate that anurans in this region are pre-adapted to coping with the changes produced by selective logging because they have evolved in a highly changeable environment. Current forestry practices are unlikely to have significant long-term negative effects if current protective measures are retained to protect identified sensitive habitats. If more intensive logging is adopted, it should be the subject of a well planned adaptive monitoring program.

Population viability of the Siberian Tiger in a changing landscape: Going, going and gone?

The Amur tiger ( Panthera tigris altaica) is a flagship species of the boreal forest ecosystem in northeastern China and Russia Far East. During the past century, the tiger population has declined sharply from more than 3000 to fewer than 600 individuals, and its habitat has become much smaller and greatly fragmented. Poaching, habitat degradation, habitat loss, and habitat fragmentation have been widely recognized as the primary causes for the observed population decline. Using a population viability analysis tool (RAMAS/GIS), we simulated the effects of poaching, habitat degradation, habitat loss, and habitat fragmentation on the population dynamics and extinction risk of the Amur tiger, and then explored the relative effectiveness of three conservation strategies involving improving habitat quality and establishing movement corridors in China and Russia. A series of controlled simulation experiments were performed based on the current spatial distribution of habitat and field-observed vital rates. Our results showed that the Amur tiger population could be viable for the next 100 years if the current habitat area and quality were well-maintained, with poaching strictly prohibited of the tigers and their main prey species. Poaching and habitat degradation (mainly prey scarcity) had the largest negative impacts on the tiger population persistence. While the effect of habitat loss was also substantial, habitat fragmentation per se had less influence on the long-term fate of the tiger population. However, to sustain the subpopulations in both Russia and China would take much greater conservation efforts. The viability of the Chinese population of tigers would rely heavily on its connectivity with the largest patch on the other side of the border. Improving the habitat quality of small patches only or increasing habitat connectivity through movement corridors alone would not be enough to guarantee the long-term population persistence of the Amur tiger in both Russia and China. The only conservation strategy that allowed for long-term persistence of tigers in both countries required both the improvement of habitat quality and the establishment of a transnational reserve network. Our study provides new insights into the metapopulation dynamics and persistence of the Amur tiger, which should be useful in landscape and conservation planning for protecting the biggest cat species in the world.

An empirical evaluation of the African elephant as a focal species for connectivity planning in East Africa

AbstractAim Large, charismatic and wide‐ranging animals are often employed as focal species for prioritizing landscape linkages in threatened ecosystems (i.e. ‘connectivity conservation’), but there have been few efforts to assess empirically whether focal species co‐occur with other species of conservation interest within potential linkages. We evaluated whether the African elephant (Loxodonta africana), a world‐recognized flagship species, would serve as an appropriate focal species for other large mammals in a potential linkage between two major protected area complexes.Location A 15,400 km2 area between the Ruaha and Selous ecosystems in central Tanzania, East Africa.Methods We used walking transects to assess habitat, human activity and co‐occurrence of elephants and 48 other large mammal species (> 1 kg) at 63 sites using animal sign and direct sightings. We repeated a subset of transects to estimate species detectability using occupancy modelling. We used logistic regression and AIC model selection to characterize patterns of elephant occurrence and assessed correlation of elephant presence with richness of large mammals and subgroups. We considered other possible focal species, compared habitat‐based linear regression models of large mammal richness and used circuit theory to examine potential connectivity spatially.Results Elephants were detected in many locations across the potential linkage. Elephant presence was highly positively correlated with the richness of large mammals, as well as ungulates, carnivores, large carnivores and species > 45 kg in body mass (‘megafauna’). Outside of protected areas, both mammal richness and elephant presence were negatively correlated with human population density and distance from water. Only one other potential focal species was more strongly correlated with species richness than elephants, but detectability was highest for elephants.Main conclusions Although African elephants have dispersal abilities that exceed most other terrestrial mammals, conserving elephant movement corridors may effectively preserve habitat and potential landscape linkages for other large mammal species among Tanzanian reserves.

Stopover ecology of a migratory ungulate

1. Birds that migrate long distances use stopover sites to optimize fuel loads and complete migration as quickly as possible. Stopover use has been predicted to facilitate a time-minimization strategy in land migrants as well, but empirical tests have been lacking, and alternative migration strategies have not been considered. 2. We used fine-scale movement data to evaluate the ecological role of stopovers in migratory mule deer Odocoileus hemionus- a land migrant whose fitness is strongly influenced by energy intake rather than migration speed. 3. Although deer could easily complete migrations (range 18-144 km) in several days, they took an average of 3 weeks and spent 95% of that time in a series of stopover sites that had higher forage quality than movement corridors. Forage quality of stopovers increased with elevation and distance from winter range. Mule deer use of stopovers corresponded with a narrow phenological range, such that deer occupied stopovers 44 days prior to peak green-up, when forage quality was presumed to be highest. Mule deer used one stopover for every 5·3 and 6·7 km travelled during spring and autumn migrations, respectively, and used the same stopovers in consecutive years. 4. Study findings indicate that stopovers play a key role in the migration strategy of mule deer by allowing individuals to migrate in concert with plant phenology and maximize energy intake rather than speed. Our results suggest that stopover use may be more common among non-avian taxa than previously thought and, although the underlying migration strategies of temperate ungulates and birds are quite different, stopover use is important to both. 5. Exploring the role of stopovers in land migrants broadens the scope of stopover ecology and recognizes that the applied and theoretical benefits of stopover ecology need not be limited to avian taxa.

Fine scale population genetic structure of pumas in the Intermountain West

In this study, I examined the population genetic structure of subpopulations of pumas (Pumaconcolor) in Idaho and surrounding states. Patterns of genetic diversity, population structure, levels of inbreeding, and the relationship between genetic differentiation and dispersal distance within and between 15 subpopulations of pumas were compared. Spatial analyses revealed that the Snake River plain was an important barrier to movement between northern and southern regions of Idaho. In addition, subpopulations south of the Snake River plain exhibited lower levels of genetic diversity, higher levels of inbreeding, and a stronger pattern of isolation by distance relative to subpopulations north of the Snake River plain. Lower levels of diversity and restricted gene flow are likely the result of historically lower population sizes in conjunction with more recent changes in habitat use and available dispersal corridors for movement. The subdivision of puma populations north and south of the Snake River plain, along with the patterns of genetic diversity within regions, indicate that landscape features are affecting the population genetic structure of pumas in Idaho. These results indicate that information about the effects of landscape features on the distribution of genetic diversity should be considered when designing plans for the management and conservation of pumas.

Independent effects of connectivity predict homing success by northern flying squirrel in a forest mosaic

Landscape composition and configuration, often termed as habitat loss and fragmentation, are predicted to reduce species population viability, partly due to the restriction of movement in the landscape. Unfortunately, measuring the effects of habitat loss and fragmentation on functional connectivity is challenging because these variables are confounded, and often the motivation for movement by target species is unknown. Our objective was to determine the independent effects of landscape connectivity from the perspective of a mature forest specialist—the northern flying squirrel (Glaucomys sabrinus). To standardize movement motivation, we translocated 119 squirrels, at varying distances (0.18–3.8 km) from their home range across landscapes representing gradients in both habitat loss and fragmentation. We measured the physical connectedness of mature forest using an index of connectivity (landscape coincidence probability). Patches were considered connected if they were within the mean gliding distance of a flying squirrel. Homing success increased in landscapes with a higher connectivity index. However, homing time was not strongly predicted by habitat amount, connectivity index, or mean nearest neighbour and was best explained as a simple function of sex and distance translocated. Our study shows support for the independent effects of landscape configuration on animal movement at a spatial scale that encompasses several home ranges. We conclude that connectivity of mature forest should be considered for the conservation of some mature forest specialists, even in forest mosaics where the distinction between habitat and movement corridors are less distinct.

Where the wisents roam

Where the wisents roam

野生動物におけるロードキル，バリアー効果とミティゲーション技術に関する研究の現状と課題

This study reviewed recent studies of road-kill, barrier effect and mitigation techniques on wild animals. It also surveyed road-crossing structures used in Japan. By comparing Japanese and international case studies, we addressed the possibility of studies on road-kill, barrier effect and mitigation technique development in Japan. The road-studies in Japan were mostly studies of the road-kill of Sika deer, Cervus nippon yesoensis, and Raccoon dog, Nyctereutes procyonoides. There were fewer Japanese studies on roadkill and barrier effect examining species, taxa, and landscapes than international studies. Most of the road-crossing structures were underpasses, box-culverts, and pipe-culverts targeting large and mid-sized mammals. There were fewer eco-bridges targeting arboreal mammals and amphibian tunnels targeting herptiles in Japan. In the future, it will be necessary to analyze the factors influencing road-kill and barrier effect of various species and taxa in order to develop mitigation techniques targeting arboreal mammals and herptiles, and to develop quantitative methods for monitoring wild mammals utilizing road-crossing structures as movement corridors.