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Over the past few decades, wildlife crossings have effectively reduced wildlife–vehicle collisions and improved habitat connectivity and genetic exchange for animals. However, wildlife crossings are expensive to construct, and the cost may discourage transportation agencies from implementing new wildlife crossings on public roadways. Additionally, transportation agencies and planners rarely consider the permitting and mitigation costs that wildlife crossings can require. A road profile must be raised to accommodate a wildlife underpass on many Florida roadways, particularly in low‐lying areas. Raising the road can result in new wetland impacts that would not occur but for the wildlife crossing. Consequently, new or more compensatory wetland mitigation may be required to satisfy § 404 of the Clean Water Act—a cost to the transportation agency and taxpayers. We used Florida's Uniform Mitigation Assessment Method (UMAM) to calculate the value of functions in habitats before and after planned wildlife crossings on State Road 40 in Volusia County, Florida. The results of our analysis show that wildlife crossings will enhance the functions in remnant habitats adjacent to the wildlife crossings, generating wetland mitigation credits that reduced the amount of compensatory wetland mitigation required by the U.S. Army Corps of Engineers. Our case study provides a novel application of the UMAM in valuing wildlife crossings. We believe the UMAM can be used in cost–benefit models and transportation planning to determine the functional value of new wildlife crossings, thereby producing a monetary value that can incentivize new wildlife crossing projects. [ABSTRACT FROM AUTHOR]

Abstract Over the past few decades, wildlife crossings have effectively reduced wildlife–vehicle collisions and improved habitat connectivity and genetic exchange for animals. However, wildlife crossings are expensive to construct, and the cost may discourage transportation agencies from implementing new wildlife crossings on public roadways. Additionally, transportation agencies and planners rarely consider the permitting and mitigation costs that wildlife crossings can require. A road profile must be raised to accommodate a wildlife underpass on many Florida roadways, particularly in low‐lying areas. Raising the road can result in new wetland impacts that would not occur but for the wildlife crossing. Consequently, new or more compensatory wetland mitigation may be required to satisfy § 404 of the Clean Water Act—a cost to the transportation agency and taxpayers. We used Florida's Uniform Mitigation Assessment Method (UMAM) to calculate the value of functions in habitats before and after planned wildlife crossings on State Road 40 in Volusia County, Florida. The results of our analysis show that wildlife crossings will enhance the functions in remnant habitats adjacent to the wildlife crossings, generating wetland mitigation credits that reduced the amount of compensatory wetland mitigation required by the U.S. Army Corps of Engineers. Our case study provides a novel application of the UMAM in valuing wildlife crossings. We believe the UMAM can be used in cost–benefit models and transportation planning to determine the functional value of new wildlife crossings, thereby producing a monetary value that can incentivize new wildlife crossing projects.

Highways can fragment habitat and be a significant mortality source for mammals. Wildlife exclusion fencing has been shown to reduce wildlife-vehicle collisions, but can also prevent animals from escaping the highway corridor if they enter at access roads or at fence ends. Earthen escape ramps, or “jumpouts,” have been proposed as a possible solution but remain relatively untested. From 2012-2014, we used wildlife cameras to continuously document wildlife use of four jumpout ramps constructed as part of a 2.5-mile wildlife exclusion fence project along Highway 101 near San Luis Obispo, California. Mule deer occasionally used the jumpouts, but quantifying the rate of utilization was confounded by repeated visits by the same individuals. Male and female deer appeared to have different responses to the jumpouts, which warrants deeper investigation using additional data collected from further monitoring through mid-2017. The longer dataset will also better document how individual deer learn to use the jumpouts. Fenced highways can also reduce connectivity unless there is sufficient use of crossing structures. We documented mountain lion, bobcat, black bear, and mule deer used culverts and underpasses in and adjacent to the wildlife fence zone from 2012-2014. Mule deer used the large underpasses almost exclusively, and rarely if ever used culverts. Bear used a wider variety of structures, and bobcats were detected at almost every site and at a higher rate than the other taxa. Mountain lion detections were quite rare, likely due to lower population density in the study area. We propose a deeper multivariate analysis of the factors influencing these species’ use of culverts including culvert dimensionality, nearby habitat, and proximity to cover, based on an expanded dataset of up to five years of continual monitoring at certain sites. The goal of these analyses is to provide information that will help reduce wildlife-vehicle collisions while facilitating regional wildlife connectivity.

Globally, human activities impact from one-third to one-half of the earth’s land surface; a major component of development involves the construction of roads. In the US and Europe, road networks fragment normal animal movement patterns, reduce landscape permeability, and increase wildlife-vehicle collisions, often with serious wildlife population and human health consequences. Critically, the placement of wildlife crossing structures to restore landscape connectivity and reduce the number of wildlife-vehicle collisions has been a hit-or-miss proposition with little ecological underpinning, however recent important developments in allometric scaling laws can be used to guide their placement. In this paper, we used cluster analysis to develop domains of scale for mammalian species groups having similar vagility and developed metrics that reflect realistic species movement dynamics. We identified six home range area domains; three quarters of 102 species clustered in the three smallest domains. We used HR0.5 to represent a daily movement metric; when individual species movements were plotted against road mile markers, 71.2% of 72 species found in North America were included at distances of less-than-or-equals, slant1 mi. The placement of wildlife crossings based on the HR0.5 metric, along with appropriate auxiliary mitigation, will re-establish landscape permeability by facilitating wildlife movement across the roaded landscape and significantly improve road safety by reducing wildlife vehicle collisions.

Highlights • We propose the Road Permeability Index (RPI) based on expert knowledge. • RPI measures potential restrictions to wildlife movement across roads. • The index varies from −1 to 1, indicating low to high chance of road crossing. • A case study compared the influences of road and landscape attributes on five taxa. • The RPI can assist on rapid assessments of road impacts on wildlife. Abstract Roads impede ecological flows through landscapes, mainly by acting as barriers to animal movement, reducing habitat connectivity and increasing animal mortality. Road permeability is not homogeneous, and animals perceive traffic and road structures differently. There is a lack of information about how species behave when they face a road. Expert knowledge is an alternative source of information when empirical data are not available. We propose the Road Permeability Index (RPI) as a formal method to incorporate expert knowledge into quantitative assessments of road permeability. We used a multi-taxon, expert-based approach that combines landscape structure and road infrastructure effects on fauna throughout landscapes. All codes are in R language, which are freely available at a GitHub repository. As a study case, we applied the RPI to 28 sampling sites along two highways in the north of São Paulo Metropolitan Region-Brazil. We used expert knowledge information on five taxa: primates, bats, medium- and large-sized terrestrial mammals, birds, and amphibians. We also propose a method to rank taxa according to their relative contribution to RPI , which enables prioritization in environmental impact assessments related to roads. For our study case, landscape and road attributes were both important for predicting road permeability, though landscape variables showed a slightly stronger average influence. RPI constitutes a replicable and easily adaptable alternative to evaluate road permeability, particularly in the absence of empirical data. RPI outcomes can inform road impact mitigation strategies and location. [ABSTRACT FROM AUTHOR]

Summary: Road escape ramps are structures developed in the USA to enable large mammals that become trapped on the roadside of a wildlife fence to escape the road and avoid vehicle collision. They are now commonly installed in eastern Australia to enable the Koala (Phascolarctos cinereus) and other fauna to escape through a roadside exclusion fence and return to the forest. We investigated the use of seven of 14 escape ramps over three years on the Oxley Highway at Port Macquarie in New South Wales. The Swamp Wallaby (Wallabia bicolor) was the most frequently detected species, traversing the escape ramps on 502 occasions, followed by bandicoots (Isoodon macrourus and Perameles nasuta) on 148 occasions. Various other species were detected but no Koalas. Swamp Wallabies moved through the escape ramps in the reverse direction (i.e. towards the road) in 53% of detections of that species and bandicoots in 14% of their detections. There was no obvious pattern by these species of proportionately higher use of ramps closer to the end of the exclusion fences. The large number of reverse passages through the escape ramps reveals a poor design of these structures. Trials with taller ramps are required to determine how to minimise reverse passages. Concurrent monitoring of three underpasses detected numerous crossings by large mammals including Swamp Wallabies, and some crossings by Koalas. We believe evidence is needed to demonstrate the necessity for escape ramps along Australian highways. [ABSTRACT FROM AUTHOR]

Road drainage structures, hereafter designated culverts, are often used by wildlife and other animals to cross under roadways. However, crossings may vary by species, culvert design, different environmental factors, and land-use and land-cover (LULC) at culvert sites. We monitored 265 culverts located throughout Maryland, USA, with motion-detecting game cameras to assess seasonal and regional effects on culvert crossing rates by wildlife and other animal species considered common to the areas. Northern raccoon (Procyon lotor) and Virginia opossum (Didelphis virginiana) exhibited lower crossing rates in culverts during winter than at other times of the year. We did not detect any difference in seasonal crossings for other species, but several species exhibited similar patterns of lower crossings/culvert/day during winter. We detected more crossings/culvert/day in the Piedmont ecoregion of Maryland for several species associated with farmland and suburbia (e.g., raccoon and red fox [Vulpes vulpes]). In contrast, opossum and free-ranging domestic cat (Felis catus) crossing rates were greater in the Appalachian Mountain ecoregion. The crossing rates for the only bird species we recorded on camera traps, the great blue heron (Ardea herodias), tended to increase from west to east, with its highest crossing rate on the Eastern Shore (lower coastal plain) of Maryland, where these birds are known to be abundant in tidal marshes. Besides a myriad of LULC and structural variables known to affect wildlife and other animal crossing rates, seasonal and regional differences in animal use must also be taken into consideration for culvert design and placement or retrofitting existing culverts to enhance crossings by particular animal species.

Millions of dollars are spent on wildlife crossing structures intended to reduce the barrier effects of roads on wildlife. However, we know little about the degree to which these structures facilitate dispersal and gene flow., Our study incorporates two elements that are rarely used in the evaluation of wildlife crossing structures: an experimental design including a before and after comparison, and the use of genetic techniques to demonstrate effects on gene flow at both population and individual levels. We evaluated the effect of wildlife crossing structures (canopy bridges and glider poles) on a gliding mammal, the squirrel glider ( Petaurus norfolcensis). We genotyped 399 individuals at eight microsatellite markers to analyse population structure, first-generation migrants and parentage relationships., We found that the freeway was not a complete genetic barrier, with a strong effect evident at only one site. We hypothesise that the presence of corridors alongside the freeway and throughout the surrounding landscape facilitated circuitous detours for squirrel gliders., Installing a crossing structure at the location with a strong barrier effect restored gene flow within just 5 years of mitigation., Synthesis and applications. Our study highlights the importance of using genetic techniques not just to evaluate the success of road-crossing structures for wildlife, but also to guide their placement within the landscape. Managers wishing to reduce the effects of linear infrastructure on squirrel gliders and other arboreal mammals should aim to preserve and enhance vegetation along roadsides and within centre medians, as well as mitigate large gaps by implementing wildlife crossing structures. [ABSTRACT FROM AUTHOR]

Gliding mammals are sensitive to habitat fragmentation that produces canopy gaps beyond their gliding capability. Specific structures (canopy-bridges and glide poles) are now commonly installed in large road construction projects to enable road crossing by threatened gliding mammals. However, these structures are being installed with limited understanding of how their design features influence their use. We conducted field testing of several design features (horizontal glide launch-beams at the top of poles; rope size and complexity in rope-bridges) using free-ranging gliding mammals, and scaled-down structures at two locations. Our aim was to identify preferred features to optimise structure use. This may confirm current designs or identify the need for refinement. We found that squirrel gliders ( Petaurus norfolcensis) and sugar gliders ( Petaurus breviceps) preferred a forward-pointing over a sideways-pointing glide beam. A single-rope rope-bridge was favoured over a mesh rope-bridge by sugar gliders but not squirrel gliders. No preference was shown by either species between mesh or ladder-style rope-bridges that differed in rope strand spacing. Large, permanently installed ladder or mesh rope-bridges commonly have single ropes connecting them to the adjacent forest. We investigated the use of a permanently installed 50-m long single-rope rope-bridge. Infra-red camera monitoring over 366 nights detected squirrel gliders on this bridge on 172 nights, common ringtail possums ( Pseudocheirus peregrinus) on 144 nights and common brushtail possums ( Trichosurus vulpecula) on 120 nights. This confirms acceptance of the single rope by a range of species and provides confidence in installing rope-bridges that may vary in rope size and complexity. [ABSTRACT FROM AUTHOR]

Road drainage structures, hereafter designated culverts, are often used by wildlife and other animals to cross under roadways. However, crossings may vary by species, culvert design, different environmental factors, and land-use and land-cover (LULC) at culvert sites. We monitored 265 culverts located throughout Maryland, USA, with motion-detecting game cameras to assess seasonal and regional effects on culvert crossing rates by wildlife and other animal species considered common to the areas. Northern raccoon (Procyon lotor) and Virginia opossum (Didelphis virginiana) exhibited lower crossing rates in culverts during winter than at other times of the year. We did not detect any difference in seasonal crossings for other species, but several species exhibited similar patterns of lower crossings/culvert/day during winter. We detected more crossings/culvert/day in the Piedmont ecoregion of Maryland for several species associated with farmland and suburbia (e.g., raccoon and red fox [Vulpes vulpes]). In contrast, opossum and free-ranging domestic cat (Felis catus) crossing rates were greater in the Appalachian Mountain ecoregion. The crossing rates for the only bird species we recorded on camera traps, the great blue heron (Ardea herodias), tended to increase from west to east, with its highest crossing rate on the Eastern Shore (lower coastal plain) of Maryland, where these birds are known to be abundant in tidal marshes. Besides a myriad of LULC and structural variables known to affect wildlife and other animal crossing rates, seasonal and regional differences in animal use must also be taken into consideration for culvert design and placement or retrofitting existing culverts to enhance crossings by particular animal species. [ABSTRACT FROM AUTHOR]

Many Eastern European countries still host landscapes with high value due to their habitat quality and size. Some of these countries are new member states of the European Union, and EU-accession is accompanied by huge investments in the development of traffic infrastructure. Environmental assessments mandatory for road constructions in the EU do not necessarily require explicit measures for the mitigation of fragmentation, and technical constructions associated with road building are frequently assumed to provide sufficient possibilities for wildlife crossings. We evaluated those technical structures at two motorway sections separating relevant subpopulations of the brown bear ( Ursus arctos) in Bulgaria. Our assessment revealed that the permeability of the two motorways has been considerably overestimated. A total of just 13 out of the 77 potential crossing possibilities of the two roads together meet the requirements we defined for suitable wildlife crossings. We found that the potential for improvement of the crossing functionality of already existing technical facilities along the motorways is very limited. Given the dependence on a small number of habitat paths connecting suitable crossings with habitat on both sides of the road, connectivity between subpopulations is vulnerable to fragmentation impacts. [ABSTRACT FROM AUTHOR]

Intuitively, wildlife crossing structures should enhance the viability of wildlife populations. Previous research has demonstrated that a broad range of species will use crossing structures, however, questions remain as to whether these measures actually provide benefits to populations. To assess this, studies will need to determine the number of individuals using crossings, their sex, and their genetic relationships. Obtaining empirical data demonstrating population-level benefits for some species can be problematic and challenging at best. Molecular techniques now make it possible to identify species, individuals, their sex, and their genetic relatedness from hair samples collected through non-invasive genetic sampling (NGS). We describe efforts to pilot a method to assess potential population-level benefits of wildlife crossing structures. We tested the feasibility of a prototype NGS system designed to sample hair from black bears (Ursus americanus) and grizzly bears (U. arctos) at two wildlife underpasses. The piloted hair-sampling method did not deter animal use of the trial underpasses and was effective at sampling hair from more than 90% of the bear crossing events at the underpasses. Hair samples were also obtained from non-target carnivore species, including three out of five (60%) cougar (Puma concolor) crossing events. Individual identification analysis revealed that three female and two male grizzly bears used one wildlife underpass, whereas two female and three male black bears were identified as using the other underpass. Of the 36 hair samples from bears analyzed, five failed, resulting in an 87% extraction success rate, and six more were only identified to species. Overall, 70% of the hair samples from bears collected in the field had sufficient DNA for extraction purposes. Preliminary data from our NGS suggest the technique can be a reliable method to assess the population-level benefits of Banff wildlife crossings. Furthermore, NGS can be an important tool for the conservation value of wildlife crossings for other taxa, and we urge others to carry out evaluations of this emerging methodology. [ABSTRACT FROM AUTHOR]

The establishment of protected areas is seen as one solution to preserve remaining components of natural ecosystems. However, the preservation role of protected areas may conflict with human activities such as industrial development and tourism. Canada's Banff National Park (BNP) hosts about 3 million visitors per year, has approximately 8000 full-time residents, and is bisected by nationally significant rail and road transportation routes. The upgrading of the Trans-Canada Highway (TCH) from two to four lanes within BNP has highlighted the park's conflicting roles. The TCH in BNP has been subject to pioneering efforts to reduce its negative effects on wildlife mortality and movement. Over 12 years of monitoring, BNP's highway mitigation measures have made this stretch of road one of the most intensely studied in the world. Both adaptive management and flexible institutional arrangements made this effort possible. The results of monitoring studies are being shared with a broad audience, from transportation practitioners and ecologists to the general public and school children. By learning more about the success of highway mitigation, a community of informed citizens is taking shape and becoming active in their understanding of nature and science. [ABSTRACT FROM AUTHOR]

Abstract: Multiple factors determine the use and effectiveness of wildlife passages and crossings installed in new roads as mitigation measures against the barrier effect. It is unknown whether factors such as seasonality determine the use of these structures. This analyses the seasonality of structure used by vertebrates. Forty-eight transverse structures crossing the A-52 motorway in north-western Spain are studied during the summer and winter of 2002–03. The use of structures by terrestrial vertebrates was monitored by tracks left in marble dust and photographic systems, and comparisons carried out by means of generalized lineal methods for count data. Structural factors mostly determined the differential use of passage types by species but seasonal changes were detected both in the intensity of use and in passage selection by some species. [Copyright &y& Elsevier]

Globally, human activities impact from one-third to one-half of the earth’s land surface; a major component of development involves the construction of roads. In the US and Europe, road networks fragment normal animal movement patterns, reduce landscape permeability, and increase wildlife-vehicle collisions, often with serious wildlife population and human health consequences. Critically, the placement of wildlife crossing structures to restore landscape connectivity and reduce the number of wildlife-vehicle collisions has been a hit-or-miss proposition with little ecological underpinning, however recent important developments in allometric scaling laws can be used to guide their placement. In this paper, we used cluster analysis to develop domains of scale for mammalian species groups having similar vagility and developed metrics that reflect realistic species movement dynamics. We identified six home range area domains; three quarters of 102 species clustered in the three smallest domains. We used HR0.5 to represent a daily movement metric; when individual species movements were plotted against road mile markers, 71.2% of 72 species found in North America were included at distances of ⩽1mi. The placement of wildlife crossings based on the HR0.5 metric, along with appropriate auxiliary mitigation, will re-establish landscape permeability by facilitating wildlife movement across the roaded landscape and significantly improve road safety by reducing wildlife vehicle collisions. [Copyright &y& Elsevier]

A major target for environmental managers when trying to minimise the road-barrier effect on wildlife is to improve permeability to animal movements. Previous studies have demonstrated that drainage culverts are used by vertebrates, although knowledge of the main influencing factors remains limited. The use of 34 culverts from two roads in southern Portugal, differing in traffic volume, vehicle speeds and configuration, was evaluated by the analysis of terrestrial vertebrate footprint data (408 passage-operative days). Culvert crossings were related to various explanatory variables by means of canonical ordination techniques. We recorded 901 complete crossings, corresponding to an average of 2.2 crossings/culvert/operative day. Thirteen taxa were detected, all in more than one passage. Animal species included reptiles, small mammals, lagomorphs, carnivores and domestic dogs and cats. Our results suggest that fencing might have a funnelling effect, directing larger animals toward culverts. Also, vegetation covering culvert entrances seems to have a positive effect, particularly on genets; longer passages with entrances far from the pavement were, apparently, avoided by smaller animals; a lower number of crossings was detected on passages with detritus pits; the closest passages to urban areas are more often used by domestic species; forest-living species favour passages with low, open land cover nearby; and smaller species, like lagomorphs and small mammals, appear to use more culverts near the pavement, which probably reflects the importance of road verges as refuges for these species. Although not used by all species present in the study area, constructing numerous passages of different sizes without detritus pits and which are distributed along roads might be an important step in mitigating road fragmentation effects on animal populations. [ABSTRACT FROM AUTHOR]