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Schematic representation of US Highway 441 across Paynes Prairie State Preserve. The road is bordered by a prefabricated concrete barrier wall and underlain by 8 culverts. Light boxes (squares) occur across the road only in the new small culverts (g, h, i, j) to allow light; a small grate is in culvert l. An access road enters on the southbound lane near the northern prairie rim (d), and a visitor turn out is located between culverts g and h. A type-A fence borders private property along the southbound lanes on the north prairie rim (b to c).
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Because of high numbers of animals killed on Paynes Prairie State Preserve, Alachua County, Florida, the Florida Department of Transportation constructed a barrier wall-culvert system to reduce wildlife mortality yet allow for passage of some animals across the highway. During a one year study following construction, we counted only 158 animals, ex...
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... eight culverts that underlie US 441 also were monitored for wildlife use. Culverts were numbered one to eight from north to south (Fig. 2). Culverts 1 and 8 were usually dry with an earthen substrate, whereas culverts 2 and 7 were inundated throughout the study. Culverts 3-6 were installed as part of the new barrier wall-culvert system. Culvert 4 was usually wet, whereas the other culverts (3, 5, and 6) were dry or wet de- pending on prairie water levels. These culverts ...
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... The conservation value of road fragmented landscapes is likely enhanced when paired with effective mitigation (Clevenger et al., 2001;Dodd et al., 2004;Jackson et al., 2015). To sustain wildlife populations in road fragmented landscapes, best management practices often recommend exclusion fencing and crossing structures as means of reducing wildlife-vehicle collisions and maintaining ecological connectivity (Rajvanshi et al., 2001;Huijser et al., 2008;Clevenger and Huijser, 2011;Gunson et al., 2016;Boyle et al., 2021). ...
Maintaining viable populations of large reptiles is often challenging in road fragmented landscapes. While mitigation structures can reduce impacts, few studies have investigated how mitigation success can be affected by roadside habitats. In southeast Ohio, USA, we evaluated mitigation effectiveness for state-endangered timber rattlesnakes ( Crotalus horridus ) at a new highway in a forested landscape. Road construction at the study site created a wide corridor of open canopy habitats (the right-of-way; ROW) containing roadcuts and stone piles. However, exclusion fencing was constructed along the forest-ROW boundary, leaving the open canopy habitats on the road-side of the fence. Over three years, we monitored 6 rattlesnakes using radiotelemetry and found that rattlesnakes repeatedly crossed the fence to access forest-edge and ROW habitats. Rattlesnakes ostensibly crossed through damaged sections of the fence. The ROW was used most intensively by gravid females (n = 2), with their core home ranges overlapping the ROW by more than 50 percent. Despite the fence crossings, all home ranges were bounded by the highway and no rattlesnake road mortality was observed. Operative temperature models revealed that the ROW provided warmer thermal regimes that were rare or unavailable in the forest. On average, field preferred gestation temperatures (T b = 29.7°C, SD = 1.8) could be attained or exceeded for more than 5 times as many hours per day in the ROW (7.8 hours) than in the forest (1.4 hours). Habitat selection models indicated gravid females selected warmer thermal habitats that were spatially concentrated in the ROW and edge habitats, while non-gravid snakes avoided the ROW beyond the forest edge. Habitat use within the ROW was mostly limited to rocky microhabitat structures, especially riprap stone piles and subsurface rock crevices on roadcuts, which provided buffered thermal regimes with refugia from extreme temperatures during the day and warmer T e through the night. In forested landscapes, we encourage road planners to consider whether new road corridors are likely to introduce basking sites, and if so, maintain those features on the habitat-side of exclusion fencing, and consider restoring basking sites in the surrounding forest to reduce the potential for ecological trap formation.
... Open-bottom culverts eliminate the potential for these issues by providing more natural flow and a contiguous natural substrate, which can also promote use by wildlife (Pagnucco et al. 2011, Kingsbury et al. 2015. Given their many additional benefits such as increased aquatic connectivity (Poplar-Jeffers et al. 2009, Evans et al. 2015 and reduced road mortality for terrestrial wildlife (Dodd et al. 2004, Glista et al. 2009), we ...
... Sparks and Gates (2012),5 Dodd et al. (2004), ...
Stable habitat connections that wildlife can safely traverse are essential to biodiversity conservation and healthy ecosystems. We developed high‐resolution landscape connectivity models to predict resistance to movement by a threatened wetland‐ obligate amphibian, the four‐toed salamander (Hemidactylium scutatum), and identified priority management areas on the 13,000‐ha Department of Energy Oak Ridge Reservation (ORR) from 2019 to 2022. We developed a resistance surface based on aerial light detection and ranging data (LiDAR), >30 years of field‐based mapping of forest, hydrologic, and geologic features, and contemporary population surveys, alongside derived predictors at <1‐m resolution. We then modeled predicted movement corridors using a circuit theory‐ based modeling approach. We worked closely with land management and natural resources personnel to integrate ecological modeling with broader land use priorities, monetary costs, and feasibility. We identified important terrestrial and aquatic areas on ORR and simulated management scenarios to promote stable connections for four‐toed salamanders. This approach allowed us to narrow down a list of 438 potential habitat manipulation sites to 10 sites where open‐bottomed culverts and buffers could be implemented. This smaller‐scale restoration approach produced a similar increase in landscape connectivity while costing <20% of a larger‐scale approach based on barrier removal. We successfully identified feasible, cost‐effective management strategies that integrated knowledge from a variety of sources. We offer a strategy that permitted integration of wildlife management goals into infrastructure upgrades wherein wildlife was not an initial consideration.
... Similarly, and in the same landscape, road-kills of leopard cats were found to be more prevalent on roads with lower traffic volume . Amphibian road-kills may be significantly mitigated by under-road tunnels with fence-end guiding structures (Helldin & Petrovan, 2019); however, barrier walls and culverts are easily climbed by hylids (Dodd, Barichivich, & Smith, 2004), so other structures such as overpasses are likely required to improve connectivity. However, there have yet to be any studies identifying structures that mitigate hylid road-kills, so more research is needed. ...
Threatened species with restricted ranges are at risk from habitat fragmentation and loss, which amplifies genetic bottleneck and impacts of small changes to their environments. Ecological models including population viability analyses (PVAs) can predict the trajectory of populations in a way that is not invasive or detrimental to the study species. They can therefore be a vital tool in modelling populations for conservation purposes. Although habitat suitability models have been used in studies to suggest areas for protected area designation, PVAs are generally not used in this regard. Dryophytes suweonensis and Dryophytes flaviventris are two threatened treefrog species endemic to the Korean Peninsula. The two species face threats of habitat loss and degradation and predation by invasive species among others. We used an integrated modelling approach combining ecological niche, connectivity, and PVAs in Vortex to determine the likelihood of extinction of each species under baseline and protected area designation scenarios. Designation scenarios were simulated in Vortex through halting future reduction in carrying capacity (halting future degradation to sites through protected area status), reducing effects of catastrophes (mitigating the effects of drought) and reducing mortality rates (controlling invasive predator populations and ex situ raising of tadpoles to maturity). We classified the combination of these management efforts as “active management” as opposed to “no management” which is currently being practiced. We additionally used a stepwise approach to determine designation priority of individual patches. Under current conditions (no management), the resulting effective metapopulations after 100 years were 167 ± 325 individuals with an 86.5% extinction probability for D. suweonensis and 165 ± 200 individuals with a 90.3% extinction probability for D. flaviventris. Under active management of all sites (93 sites covering 426.9 km2), the extinction probability was 0% for both species with significantly increased metapopulation sizes, 15,910 ± 2,855 for D. suweonensis and 4,400 ± 874 for D. flaviventris. Determining designation priority can inform the regulatory bodies on which habitat to designate and whether active or passive management should be applied. Without intervention, these species will be likely to face imminent extinction. In addition to being useful for government-imposed conservation management, our study can be followed by future studies as a methodology for prioritizing sites for protected area designation.
... On the other hand, we expected the presence of fences to reduce animal roadkills, since they would avoid the passage of many animals (McCollister and Van Manen 2010). However, most of the fenced road sections had a generalist one, which only impedes the crossing of large mammals, allowing micro and mid-mammals, as well as reptiles and amphibians, to cross it easily (Dodd et al. 2004). In addition, the fencing at most points of the study roads was in poor condition (pers. ...
Due to rapid human expansion in the last century, wildlife roadkill is becoming a concerning threat to biodiversity and human safety. The frequency of roadkill events depends on factors related to specific traits of the road—tortuosity or the presence of fences, among others—and the animal ecology—such as activity patterns, reproductive season, or thermoregulation. These, in turn, are related to environmental factors, with seasonal variations. Here, we assessed roadkill mortality of terrestrial vertebrates over the year. To do this, we sampled 10 road sections (of 3 km, by walk) in the south of Spain for a full year, registering the carcasses of run-over vertebrates. Then, we analysed the spatiotemporal patterns of roadkill events for the four vertebrates’ classes and the effects of road traits (presence of fence, tortuosity, distance to water point) and environmental variables (mean temperature and precipitation). Mammals suffered the highest mortality by roadkill (45.72%). The frequency of collisions was independent of tortuosity, presence of fences, and precipitation, while mean temperature significantly increased the probability of collision of mammals, birds, and reptiles. There was a seasonal effect in the number of collisions, which spatial pattern depended on the class of vertebrates. All this leads us to conclude that, to reduce the impact caused by roadkill mortality on wildlife, we need specific measures to be taken timely in each critical place and for each vertebrate group.
... Brunen's research recommends that the construction of drainage culverts in combination with fences will effectively reduce wildlife mortality [23]. Kenneth and Clevenger's also suggested reducing road noise and creating appropriate culvert sizes to promote the use of culverts by mammals [22,53]. A substantial network of roads totaling 1192 km is located within the giant panda habitat in Sichuan Province [35]. ...
Roads, acting as barriers, hamper wildlife movements and disrupt habitat connectivity. Bridges and culverts are common structures on roads, and some of them can function to allow wildlife passage. This study investigated the effects of traffic, the surrounding landscape, human disturbance, and bridge and culvert structures on the utilization of bridges and culverts as dedicated passages by wildlife, using motion-activated infrared camera traps along a 64 km road in Giant Panda National Park, Sichuan, China. The results show that both species richness and counts of wildlife recorded at the bridge and culvert were significantly lower than those observed at sites distant from roads. No large-sized wildlife was recorded at the bridges and culverts. Human activities and traffic volume significantly and negatively affect medium-sized wildlife utilization of bridges and culverts. We conclude that bridges and culverts serve as wildlife crossings, but their efficacy is weak. This emphasizes the necessity of retrofitting bridges and culverts via mitigation facilities such as noise and light barriers, and vegetation restoration on both sides of the roads in Giant Panda National Park.
... There are sections outside of towns where culvert passages with barrier walls under the road could be a feasible solution to reduce snake mortality (Dodd et al. 2004). However, it is important that these are designed properly, e.g. they are wide enough to be used by snakes or other animals because a passage itself does not guarantee that animals will use it (Baxter-Gilbert et al. 2015). ...
Flood protection measures can have large impacts on ecosystems and their biodiversity, yet direct comparisons of active and inactive floodplains are rare. We compared the number of roadkilled individuals of two semiaquatic water snakes ( Natrix natrix and N. tessellata ) on 58 km of road sections bordered either by an active floodplain or a flood-protected former floodplain in NE Hungary based on surveys conducted once every two weeks in three years. We found unexpectedly high road mortality of snakes, which was rather similar across years. Mortality had a spring and an autumn peak, corresponding to the times when snakes emerge from and return to hibernating sites. Road mortality was more severe and more predictable in the flooded than in the flood-protected area, even though traffic was more intense in the latter. Our results show that small-scale spatial differences in road mortality are mediated by landscape structure along the road, while the effects of traffic intensity and the age and sex of the individuals were negligible. For conservation implications, our study suggests that establishing culvert passages under the road and artificial hibernating sites on the floodplain-side of the roads in critical sections to reduce the road-related mortality.
... Increasing attention is being paid to mitigating the impacts of road mortality on amphibians by installing tunnels or culverts underneath roads that facilitate the safe passage of individuals between habitats that are crucial to complete their life cycle (underroad tunnels; Beebee, 2013;Helldin and Petrovan, 2019). In Europe and North America, under-road tunnels have been designed and built in a variety of forms, from concrete box culverts (Dodd et al., 2004) to cast-iron tunnels (Zuiderwijk, 1989) and polymer concrete tunnels specifically designed for small animals (e.g. amphibian tunnels manufactured by ACO: Langton, 1989;Matos et al., 2017;Jarvis et al., 2019;Ottburg and van der Grift, 2019). ...
... The mean numbers of European tree frogs (Hyla arborea) AOR and DOR were estimated to be higher at tunnels closest to breeding ponds, where individuals may be climbing over the fences and walls and onto the road. Elsewhere, barrier and culvert systems had no effect on reducing large numbers of Hyla species killed on a road traversing a large wetland (Dodd et al., 2004). Preventing road mortality for tree frogs is therefore likely to be difficult but removing vegetation from barrier walls and fences may reduce trespass rates (Dodd et al., 2004). ...
... Elsewhere, barrier and culvert systems had no effect on reducing large numbers of Hyla species killed on a road traversing a large wetland (Dodd et al., 2004). Preventing road mortality for tree frogs is therefore likely to be difficult but removing vegetation from barrier walls and fences may reduce trespass rates (Dodd et al., 2004). If resources for maintaining fencing are limited, then it might be best to prioritise regular maintenance at sections close to breeding ponds. ...
Road traffic often inflicts higher mortality rates on amphibians than other vertebrates, especially where roads bisect migration pathways. To facilitate safe movements by amphibians between non-breeding and breeding habitats, under-road tunnels are being increasingly installed together with barrier fencing or walls. However, few observational studies have correlated aspects of road mitigation placement and design with amphibian population sizes. Here, we assessed the effectiveness of 13 under-road tunnels (ten cylindrical and three square-shaped) along a two-lane sealed road in northern Hungary positioned between upland forest habitat and a floodplain containing breeding ponds. Amphibian count surveys at tunnels and along road transects above tunnels were conducted at night during the spring migration period from 2009 to 2012. We detected a total of seven amphibian species, with the common toad (Bufo bufo) representing > 90% of individuals counted. Using community N-mixture modelling, we found that tunnels with larger-sized entrances and tunnels positioned near other tunnels had higher amphibian abundance. We also found that road mortality was higher above tunnels closest to breeding ponds for some species. Moreover, tunnel usage rates and road mortality rates were far lower and higher, respectively, than other studies that assessed similar species along European roads. These results imply that barrier walls and fencing were largely ineffective at directing amphibians towards the tunnels and were not preventing amphibians from accessing the road surface. Our results demonstrate the importance of placement and design in the usage of under-road tunnels by amphibians but underscore the need to maintain barrier fences and walls to reduce road mortality rates and connect amphibian habitats.
... Many amphibians undertake spring and autumn migrations, which renders them particularly sensitive to roads between the various key areas used during the different phases of their life cycle (Wilbur, 1980;Miaud et al., 2000;Semlitsch, 2008;Joly, 2019;Cayuela et al., 2020). Even outside the migration periods, roads disrupt the movement of individuals between local populations and, furthermore, increase mortality through roadkill, potentially leading to the extinction of local and regional amphibian populations (Fahrig et al., 1995;Dodd et al., 2004;Petrovan and Schmidt, 2016;Testud and Miaud, 2018;Joly, 2019). ...
... The last measure is often associated with fences (e.g., wire netting, plastic mesh, or full panel concrete or metal), constructed to prevent animals from venturing onto roads and guide them instead towards passages (under/overpasses), where they can safely cross a road (Schmidt et al., 2008;Arntzen et al., 2017;Carvalho et al., 2017;Testud and Miaud, 2018). These fences are typically designed for large fauna (large meshsize), such as ungulates (e.g., deer; Fahrig et al., 1995;Romin and Bissonette, 1996;Clevenger and Waltho, 2000;Forman et al., 2003;Dodd et al., 2004;Glista et al., 2009), but often contain additional components (fences with a small mesh-size), to stop amphibians and small mammals (Morand and Carsignol, 2019). Large fauna fences have been relatively well studied (i) because they are of obvious interest for human safety (Romin and Bissonette, 1996;Schwabe et al., 2002;Forman et al., 2003;Bouffard et al., 2012) and (ii) because their effectiveness can be easily demonstrated by monitoring the number of collisions between ungulates and vehicles. ...
... For small fauna, different types of fences have been used but their effectiveness has rarely been studied. The few studies that have been carried out suggest a low efficacy of such fences (Dodd et al., 2004;Woltz et al., 2008;Brehme et al., 2021;Conan et al., 2022). For example, Arntzen et al. (1995) tested the effectiveness of chicken wire (40 cm height, 10 cm overhang, 1.3 cm mesh size) and plastic mesh fences (50 cm height, 10 cm overhang, 0.3 cm mesh size) to avoid amphibian road crossings (toads and newts, respectively). ...
To mitigate habitat fragmentation and roadkill, roads are increasingly equipped with wildlife fences and underpasses. However, the effectiveness of such fences in preventing road access for amphibians has not been tested under controlled conditions. In 2019 and 2020, we tested the efficacy of full panel fences of differing material, height, and shape (presence/absence of an overhang), to prevent road access for adult and juvenile amphibians. We selected five species according to locomotion mode: Natterjack toads (runners), European green toads (short-distance jumpers), agile frogs (proficient jumpers), American tree frogs (proficient climbers) and smooth newts (climbers). We found that Natterjack and green toads were unable to cross a concrete fence with a height of 13 and 24 cm, respectively. Addition of a 10 cm overhang reduced the height required to prevent crossing further to 10 and 17 cm, respectively. The ability of these less agile species to cross a certain fence height depended on body length. By contrast, jumping agile frogs and climbing tree frogs were not stopped by the greatest fence height tested (40 cm). However, addition of the overhang stopped the climbing tree frogs at a concrete fence height of 35 cm. An alternative metal fence (with overhang) was tested with some species and performed similar to the concrete fence (with overhang). Finally, the greatest concrete fence height passed by climbing juveniles was 20 cm (smooth newts). Hence, to stop amphibians from road crossing, we recommend the construction of durable (concrete or galvanized metal) and well-maintained fences with a minimum height of 40 cm with a 10 cm overhang.
... It is estimated that upwards of 365 million vertebrates are killed each year in the United States (FHWA 2008) from vehicle collisions. Road characteristics such as number of lanes, posted speed limits, traffic volumes, and the grade of the road (level or above the surrounding environment) influence the overall number and type of species that are vulnerable to wildlife-vehicle collisions (Dodd et al. 2004). Mammals, specifically small mammals (Figure 3), were found to be the most killed species along roads, followed by birds, then reptiles (Magioli et al. 2019;Gonzalez-Gallina et al. 2013). ...
... However, fencing alone further exacerbates the barrier effect of roads(Jaeger et al. 2005). Fencing that funnels wildlife towards wildlife crossing structures can reduce the number of wildlife vehicle collisions while allowing for movement across the landscape(FHWA 2008;Dodd et al. 2004;Jaeger et al. 2005). For example, fencing and wildlife crossing structures were installed for the Florida Key deer during the widening of US Highway 1 in the Florida Keys, successfully mitigating the increased wildlife vehicle collision threat from the additional lane (USFWS 2019c). ...
Roads impact a disproportionately larger area than the land area that they occupy, often called the road effect zone. This effect extends to wildlife populations. Impacts on federally listed species include habitat loss and fragmentation, road mortality, the barrier effect, and the habituation effect. Per the Endangered Species Act, these impacts must be assessed before roadway impacts occur. This publication provides an overview of the potential impacts to 29 of Florida’s threatened and endangered animal species from roads. Potential mitigation options include road configuration, signage, speed limits, habitat protection, improved technology, wildlife fencing, and wildlife crossing structures. The goal is to educate transportation engineers and planners to allow for sustainable transportation infrastructure growth while protecting, conserving, and ultimately recovering Florida’s threatened and endangered species.
... Mitigation measures should entail the reduction of traffic in the city, increasing green areas instead of pavement and whenever possible avoiding road construction. In addition, implementation of culverts was shown to reduce roadkill incidents of amphibians and other small animals [53,54]. Given the lack of green toads in densely populated areas, open corridors between existing populations may allow animal movement and reduce the risk of inbreeding [55,56]. ...
Urban areas are increasing worldwide, which poses threats to animal wildlife. However, in certain cases cities can provide refuges for endangered animals. The European green toad (Bufotes viridis) is one of such examples, which is known from cities throughout their distribution. In contrast, considerable areas of their former (primary) habitats have been degraded. The primary habitats of this species include steppes and wild river floodplains, both characterized by dynamic changes and the presence of open areas. We used available green toad observation data (2007–2020) to model the effects of land-use types on occurrence probability in the city of Vienna. Forest and densely populated areas were highly significantly negatively associated with green toad presence, while transformation/construction site areas showed a strong positive effect. Such occurrence pattern might be characteristic for early succession species, which depend on stochastic environmental disturbances (e.g., droughts and floods) in their primary habitats. We argue that urban landscape planning should appreciate the potential ecological value of open land in cities which is either in a transition phase or a permanent ‘wasteland’. Ecological managing of such landscape could vastly increase urban biodiversity.
