Roadkill Hotspots Research Articles

Wildlife roadkill in the Tsavo Ecosystem, Kenya: identifying hotspots, potential drivers, and affected species

Roadkill is one of the highest causes of wildlife mortality and is of global conservation concern. Most roadkill studies have focused on wildlife in developed countries such as the United States of America and temperate biomes, but there are limited data for the impacts of roads on wildlife in the African tropics, where road infrastructure development is projected to grow rapidly in natural environments and conservation areas. The Tsavo Conservation Area is an important biodiversity hotspot in eastern Kenya and is bisected by a major highway and railways that connect the port of Mombasa to the interior. Along this infrastructure corridor, roadkill was recorded for 164 days over an 11-year period (2007–2018). In total, 1,436 roadkill were recorded from 13,008 km driven of a 164.42 km Nairobi-Mombasa road representing 0.11 collisions per kilometer. The majority of roadkill were small to medium sized mammals (<15kg) (53%; n = 756), whereas birds comprised 32% (n = 460), reptiles 10% (n = 143), with the remaining 5% (n = 77) being large mammals (>15kg). Of the 460 birds recorded, 264 were identifiable represented by 62 species. All large mammals comprising 10 species were identified, including the African elephant, Loxodonta africana and the endangered African wild dog, Lycaon pictus. Thirteen species of small mammal were also identified dominated by Kirk's dik-dik (Madoqua kirkii). Reptiles were represented by 11 species which were identified to the species level. Roadkill hotspots were identified using a kernel density method. The spatial distribution of roadkill was associated with adjacent shrub vegetation and proximity to permanent and seasonal rivers, and differences in seasonality and habitats were observed. Roadkill was lowest on road sections that traversed settled areas as opposed to roads adjacent to the protected areas. The results demonstrate that roadkill for two of the taxonomic groups - mammals and birds - appear high with numerous species detected in the Tsavo Conservation Area. These results can be used to focus efforts to reduce wildlife mortality by guiding future mitigation efforts.

Snakes on a lane: Road type and edge habitat predict hotspots of snake road mortality

Roads constitute just 1% of the total land in the US, but their impacts on wildlife are significant and far-reaching. Snakes are particularly susceptible to road mortality because many species do not avoid crossing roads, may use the road’s surface to thermoregulate, or freeze when approached by a vehicle. We conducted opportunistic surveys to collect road mortality points for snakes in southeastern Ohio over 15 years (2003–2018). We used logistic regression to predict roadkill hotspots and evaluate variables that influence road mortality. The species most frequently found dead on roads were Black Ratsnakes (Pantherophis spiloides), Northern Black Racers (Coluber constrictor), Eastern Gartersnakes (Thamnophis sirtalis), and Rough Greensnakes (Opheodrys aestivus). Across the 14 snake species we recorded dead on roads, percent pasture within a 100 m buffer of the roadkill point, township route, county route, and state route were all negative predictors of road mortality. All surveys started in Athens, Ohio, and distance to roadkill locations was a positive predictor for road mortality. These results indicate that high-traffic roads pose a risk to snake populations, but that mortality also occurs on low-traffic roads as well. Our top model showed that low levels of pasture embedded in other land cover types was an important predictor of roadkill, suggesting that edge habitat contributes to snake road mortality. Because road mortality does not seem to be localized, road mortality mitigation structures such as underpasses and fences may have limited benefits for snake populations in our study area. The creation of edge habitat away from roads could provide snakes with necessary habitat without increasing their risk of mortality.

Herpetofauna Roadkills on Langkawi Island, Peninsular Malaysia: The Influence of Landscape and Season on Mortality Distribution

We examined the spatiotemporal variation of herpetofauna roadkills on roadways in Langkawi Island. A total of 131 roadkills were recorded. The species that exhibited greater mortality was Varanus nebulosus (n=72). There was a significant difference in herpetofauna mortality between dry and wet seasons (t(11) =-2.330, p=0.04, <0.05). The spatial pattern was described by using kernel density estimation. Four collision hotspots were concentrated at the west side of the island, adjacent to vegetation area and forest reserve. Species characteristics, road proximity to the forested area, vegetation cover and traffic volume may influence the high rate of roadkills found. Installation of warning signs, speed restrictions and temporary road closings could reduce traffic accident and significantly reduce mortalities. The study represents a significant improvement over previous research on the island by implementing hotspot analysis. We would suggest analysing habitat suitability and connectivity to increase the ability to predict the location of roadkill hotspots.

Spatiotemporal persistence of bat roadkill hotspots in response to dynamics of habitat suitability and activity patterns

Wildlife roadkill hotspots are frequently used to identify priority locations for implementing mitigation measures. However, understanding the landscape-context and the spatial and temporal dynamics of these hotspots is challenging. Here, we investigate the factors that drive the spatiotemporal variation of bat mortality hotspots on roads along three years. We hypothesize that hotspot locations occur where bat activity is higher and that this activity is related to vegetation density and productivity, probably because this is associated with food availability. Statistically significant clusters of bat-vehicle collisions for each year were identified using the Kernel Density Estimation (KDE) approach. Additionally, we used a spatiotemporal analysis and generalized linear mixed models to evaluate the effect of local spatiotemporal variation of environmental indices and bat activity to predict the variation on roadkill hotspot locations and to asses hotspot strength over time. Between 2009 and 2011 we conducted daily surveys of bat casualties along a 51-km-long transect that incorporates different types of roads in southern Portugal. We found 509 casualties and we identified 86 statistically significant roadkill hotspots, which comprised 12% of the road network length and contained 61% of the casualties. Hotspots tended to be located in areas with higher accumulation of vegetation productivity along the three-year period, high bat activity and low temperature. Furthermore, we found that only 17% of the road network length was consistently classified as hotspots across all years; while 43% of hotspots vanished in consecutive years and 40% of new road segments were classified as hotspots. Thus, non-persistent hotspots were the most frequent category. Spatiotemporal changes in hotspot location are associated with decreasing vegetation production and increasing water stress on road surroundings. This supports our hypothesis that a decline on overall vegetation productivity and increase of roadside water deficit, and the presumed lower abundance of prey, have a significant effect on the decrease of bat roadkills. To our knowledge, this is the first study demonstrating that freely available remote sensing data can be a powerful tool to quantify bat roadkill risk and assess its spatiotemporal dynamics.

Importance of professional roadkill data in assessing diversity of mammal roadkills

With considerable under-reporting of roadkills, the impact of transport on biodiversity is mostly underestimated. The main goal of this study was to compare official roadkill records with data collected by professional biologists. On roads with different traffic intensities, we compared species richness, diversity indices and species composition with regard to the data sources and performed roadkill hotspot analysis. Biologists recorded more mammal species killed, a higher diversity index and a different composition of dominants in the roadkills, as well as different numbers and locations of hotspots. Traffic intensity and population size explained 63–93% of the variation in roadkill numbers in ungulates. Professional monitoring effort and traffic intensity explained nearly 90% of variation in roadkill numbers, 70% of variation in recorded species and 40% of diversity variation. With greater accuracy than available official data, professional roadkill diversity data should be used in wildlife-vehicle accident analysis and in planning road safety infrastructure.

The Australian Roadkill Reporting Project-Applying Integrated Professional Research and Citizen Science to Monitor and Mitigate Roadkill in Australia.

Simple SummaryAustralia has no database of national roadkill. The current research project fills that knowledge gap by developing a roadkill reporting application that enables professional and citizen scientists to record photographs of roadkill with location, time and date. This embodies the concept of ‘One Welfare’ as it affects humans, animals and the environment. Uploaded to a website, these data can identify roadkill hotspots, tabulate species of animals killed and potentially be used for ecological studies of roadkill numbers, species distribution, population trends, animal behaviour and disease. Initial results indicate that mammal roadkill mostly occurs at night and that of birds and reptiles during daytime. Mammals make up three-quarters of the roadkill recorded and this includes endangered species. Two examples of roadkill hotspots are shown in Queensland and Tasmania. These will enable further research to suggest how roadkill mitigation measures may be optimally employed.Australia has no national roadkill monitoring scheme. To address this gap in knowledge, a roadkill reporting application (app) was developed to allow members of the public to join professional researchers in gathering Australian data. The app is used to photograph roadkill and simultaneously records the GPS location, time and date. These data are uploaded immediately to a website for data management. To illustrate the capacity to facilitate cost-effective mitigation measures the article focuses on two roadkill hotspots—in Queensland and Tasmania. In total, 1609 reports were gathered in the first three months of the project. They include data on mammals (n = 1203, 75%), birds (n = 125, 7.8%), reptiles (n = 79, 4.9%), amphibians (n = 4, 0.025%), unidentified (n = 189, 11.8%) and unserviceable ones (n = 9). A significant finding is variance in the distribution of mammals and birds at different times of day. These findings reflect diurnal variation in the activity levels of different species and underline the need for data on a targeted species to be collected at appropriate times of day. By continuing to facilitate roadkill monitoring, it is anticipated that the data generated by the app will directly increase knowledge of roadkill numbers and hotspots. Indirectly, it will provide value-added information on animal behaviour, disease and population dynamics as well as for species distribution mapping.

An adaptive plan for prioritizing road sections for fencing to reduce animal mortality.

Mortality of animals on roads is a critical threat to many wildlife populations and is poised to increase strongly because of ongoing and planned road construction. If these new roads cannot be avoided, effective mitigation measures will be necessary to stop biodiversity decline. Fencing along roads effectively reduces roadkill and is often used in combination with wildlife passages. Because fencing the entire road is not always possible due to financial constraints, high-frequency roadkill areas are often identified to inform the placement of fencing. We devised an adaptive fence-implementation plan to prioritize road sections for fencing. In this framework, areas along roads of high, moderate, and low levels of animal mortality (respectively, roadkill hotspots, warmspots, and coldspots) are identified at multiple scales (i.e., in circles of different diameters [200-2000 m] in which mortality frequency is measured). Fence deployment is based on the relationship between the amount of fencing being added to the road, starting with the strongest roadkill hotspots, and potential reduction in road mortality (displayed in mortality-reduction graphs). We applied our approach to empirical and simulated spatial patterns of wildlife-vehicle collisions. The scale used for analysis affected the number and spatial extent of roadkill hot-, warm-, and coldspots. At fine scales (e.g., 200 m), more hotspots were identified than at coarse scales (e.g., 2000 m), but combined the fine-scale hotspots covered less road and less fencing was needed to reduce road mortality. However, many short fences may be less effective in practice due to a fence-end effect (i.e., animals moving around the fence more easily), resulting in a trade-off between few long and many short fences, which we call the FLOMS (few-long-or-many-short) fences trade-off. Thresholds in the mortality-reduction graphs occurred for some roadkill patterns, but not for others. Thresholds may be useful to consider when determining road-mitigation targets. The existence of thresholds at multiple scales and the FLOMS trade-off have important implications for biodiversity conservation.

Do turtle warning signs reduce roadkill?

Roadkill is a serious threat for many species of freshwater turtles. One of the most common road mitigation tools is wildlife warning signs to alert drivers. These warning signs have commonly been used for large mammals, although there is little evidence that they are effective in reducing roadkill. We tested the effectiveness of turtle warning signs at four known roadkill hotspots along a provincial highway in eastern Ontario and compared the results with four control sites on a nearby major road in a before-after-control-impact (BACI) study. We found 30 dead turtles in the four hotspots in 2017 before the signs were installed and 27 in 2018 after the signs were installed. The number of turtles killed on the road after the signs were installed did not change significantly (χ21 = 1.1, P &gt; 0.2). Although turtle warning signs may alert some drivers, they should not be considered a replacement for more effective road mitigation tools, such as wildlife fencing and crossing structures.

Are Roadkill Hotspots in the Cerrado Equal Among Groups of Vertebrates?

Understand the spatial distribution of wildlife roadkill is necessary to design mitigation measures minimizing damage to the fauna and the human population. Thus, we aimed to analyze the spatial distribution of wildlife roadkill in the Brazilian savanna ("Cerrado") to test whether roadkill hotspots match between the studied animal groups. We collected data of wildlife roadkill over a year in the southwest region of the state of Goiás, Brazil. To understand the distribution of roadkill on highways and to identify the aggregation hotspots, we used the modified two-dimensional Ripley K test and the two-dimensional hotspot identification analysis. We detected that birds and mammals have different aggregation points. These points may vary when the two groups are analyzed together or when species with greater abundance are removed from the analyses. Hence, we concluded that using generalist approaches including several species, are not enough, and can lead to erroneous conclusions. Therefore, it is necessary that the analyses be done in groups.

SPATIO-TEMPORAL PATTERNS OF MAMMAL ROAD MORTALITY IN MIDDLE MAGDALENA VALLEY, COLOMBIA

Wildlife-vehicle collisions are acknowledged as the leading source of vertebrate mortality worldwide. Here, we examined spatio-temporal patterns of mammal road mortality in three routes on a fragmented landscape in the Middle Magdalena Valley, Santander department, Colombia. We identified the species affected by road mortality, estimated the roadkill rates for each road segment, and identified roadkill hotspots related to multi-scale structural connectivity. During an eigth-month period, we recorded a total of 152 mammal roadkills of 12 native species. The roads with the highest roadkill rates were Departmental Route 01 (DR01) and National Route 66 (NR66), but roadkill aggregations corresponding to potential roadkill hotspots were only identified on the route DR01. These hotspots intersect with sections of the landscape with lower connectivity, suggesting that mammal species are forced to leave suitable habitats in response to habitat fragmentation, increasing the risk of wildlife-vehicle collisions. Our results contribute to understanding spatio-temporal factors potentially promoting mammal roadkill events and offer a unique opportunity to designing effective mitigation measures that will work properly.

SEASONAL AND SPATIAL VARIATION OF ROAD-KILLED VERTEBRATES ON BR330, SOUTHWEST BAHIA, BRAZIL

In the present study, we aimed to characterize and quantify the vertebrates road-killed along 12.8 km of the BR-330 highway in southwestern Bahia. The road is surrounded by patches of Atlantic Forest and Caatinga and by human-modified areas. From May/2012 to August/2013, we performed 35 surveys, monitoring 448 km in total. During this period, we registered 146 road-killed individuals belonging to 60 species (35 birds, 15 reptiles, 7 mammals and 3 amphibians). The species most likely to be road-killed in the study area were the toad Rhinella jimi and the snakes Oxyrhopus trigeminus and Sibynomorphus neuwiedi . The Jaccard index showed higher values when compared to the observed richness of road-killed species, which is corroborated by the ten new species recorded during five additional surveys from August/2015 to July/2016. The number of road-killed vertebrates was significantly higher in the rainy season than in the dry season. We identified 26 road-kill hotspots along the studied stretch of road. The presence of water bodies associated with vegetational landscape surrounding these hotspots may be a reason for the higher concentration of road-kills. Besides being one of the few studies conducted in an ecotonal area in the northeast of Brazil, our data indicate some important patterns that should be considered for regional and national policies on impact mitigation.

Spatiotemporal identification of roadkill probability and systematic conservation planning

Accurate spatiotemporal modeling of roadkill hotspots is essential for the assessment of high risk roadkill locations. Increasing the spatiotemporal resolution of models may facilitate greater cost-effective solutions for roadkill mitigation strategies. This study develops a novel spatiotemporal roadkill distribution model to simulate roadkill probability. Moreover, we systematically identify top prioritized road segments by the most frequent roadkill occurrence for multiple focal species. Based on the theory of the Poisson process, the proposed spatiotemporal roadkill distribution model with seasonal effects is validated with four focal reptilian species. The model simulates spatiotemporal roadkill patterns and addresses uncertainty by referencing ensemble species distribution models. Finally, we systematically prioritize road segments by the most frequent roadkill occurrence for multiple focal species. The efficacy of the proposed spatiotemporal roadkill distribution model which is validated in terms of the area under the receiver operating characteristic curve (AUC) and accurate proportions. The AUC values based independent roadkill data tests ranged from 0.73 to 0.84. Both the efficacy of the proposed model, and the increases in uncertainty are attributable to decreasing seasonal sampling size and variation. Based on the independent roadkill data, more than 70% of roadkill events occurred within the top 30% priority segments by our approaches. The proposed model is successfully applied in simulation of spatiotemporal roadkill probability. The seasonal effects benefit identification of high roadkill probability. Through the systematic identification and the proposed model, our approach provides useful information for the design of cost-effective surveys and appropriate conservation planning and mitigation strategies.

SHORT AND NARROW ROADS CAUSE SUBSTANTIAL IMPACTS ON WILDLIFE

Short and narrow roads are generally overlooked when assessing road impacts on biodiversity. However, these roads bisect natural environments and may cause significant impacts on wildlife in local scale. Thus, we monitored roadkills along a short two-lane road (CPM road) in Southeastern Brazil and propose mitigation strategies to reduce wildlife mortality. We monitored roadkilled vertebrates along 5 km of CPM road from 2010 to 2016 and we also compiled data from previous studies along the same road. We conducted a hotspot analysis to identify CPM road areas with significant roadkill aggregation. We recorded 77 roadkilled vertebrates from 14 taxonomic groups along the CPM road. Mammals were the most frequently recorded group (91% of roadkills), which represented 56% of all medium- and large-sized mammal species known to occur in the study area. We identified three roadkill hotspots along the CPM road. Two of them were located at two stream crossings, where the road cut across the associated riparian forests, and the other was at a road section with water drainage from a pond, also connected to a riparian forest. These riparian forests are part of the remaining natural habitat that provides connectivity between the forest remnants in the landscape, and therefore, for wildlife. Our results showed that even short and narrow roads can have considerable roadkill, which may have severe effects for wildlife on a local scale. The results stress the need to carefully look at these types of roads and propose measures to reduce impacts. We propose the creation of safe crossing opportunities in the hotspot zones combined with wildlife fencing to keep the animals off the road and guide them towards the safe crossing opportunities.

Modeling fall migration pathways and spatially identifying potential migratory hazards for the eastern monarch butterfly

Identifying core migratory pathways and associated threats is important for developing conservation priorities for declining migratory species, such as eastern monarch butterflies (Danaus plexippus L.). Characterization of monarch fall migration core pathways and annual variability was compared using kernel density estimation models (KDEMs) and MaxEnt ecological niche models. Potential anthropogenic hazards were identified across migratory pathways and related to conservation strategies. Journey North citizen scientist monarch overnight roost data from 2002 to 2016 were used to model the fall migration at 10 km spatial resolution with MaxEnt and KDEMs. Potential anthropogenic threats to the fall migration were spatially identified along core migratory routes. The KDEM migratory pathways best represented patterns of monarch movement towards overwintering locations. Migratory routes varied as much as 200 km from east to west in the southern Central Flyway, which was also the only area identified with monarch roadkill hotspots. Potential threats from mosquito adulticide ultra-low volume (ULV) spraying were concentrated along Eastern Flyway coastal areas. Potential nectar resource loss or contamination from high usage of glyphosate herbicide and neonicotinoid insecticides was greatest in the Midwest, within the core route of the Central Flyway. MaxEnt and KDEM were complementary in modeling monarch migratory pathways. Monarch roadkill estimation and mitigation strategies are most needed in the southern core migratory pathways through Texas and Mexico. High quality nectar resource enhancement could help to mitigate potential threats from mosquito ULV spraying and nectar resource loss or contamination in coastal areas and the Midwest, respectively.

Do roadkill aggregations of wild and domestic mammals overlap?

Domestic animals are involved in a large number of traffic accidents and they represent danger to humans due to their size. Despite this, few studies consider domestic animals. That is why we evaluate mammals’ roadkill aggregations in order to locate them and to determine if wild and domestic mammals’ roadkills overlap. In addition, we investigate the influence of the landscape on the location of the aggregations. This study was carried out on the BR-050 highway, an area of Cerrado biome, in Southeastern Brazil. The monitoring was executed from April 2012 to March 2013, by car, at an average speed of 60 km/h, with two observers looking for roadkills on the highway. We found 482 mammals’ roadkills, including 260 (54 %) wild mammals, 164 (34 %) domestic and 58 (12.0 %) undetermined specimens. Of the 21 recorded mammal species, five were domestic. The wild mammals’ roadkill rate was 0.03 (± 0.02) individuals/km/day and the domestic roadkill rate was 0.02 (± 0.01). We detected roadkill aggregations for wild and domestic mammals. Roadkill hotspots of domestic mammals and wild mammals did not overlap. The variables that had the highest influence on wild mammals’ roadkill probability were: agriculture and silviculture cover as positive effects and distance to the nearest river, to the urban perimeter and to a natural fragment as negative effects. For domestic mammals these variables were: area of the smallest fragment and distance to a natural fragment as positive effects and silviculture cover as a negative effect. The explanation for the wild and domestic mammals’ roadkill hotspot non overlapping seems to be the effect of each variable in determining the roadkill hotspot since their effect is different for wild and domestic mammals. On the other hand, this non overlapping can be a result of domestic mammals’ scavenging habits. We propose different kinds of mitigation measures in order to reduce domestic and wild mammals’ roadkill.

Spatial risk assessment of eastern monarch butterfly road mortality during autumn migration within the southern corridor

Road mortality may contribute to the population decline of eastern monarch butterflies (Danaus plexippus L.). We estimated autumn monarch roadkill rates within the primary Oklahoma to Mexico southern migration corridor (i.e., Central Funnel). Dead monarchs were surveyed along Texas roadsides during four weeks of autumn migration in 2016 and 2017. Roadkill averaged 3.4 monarchs per 100 m transect, reaching 66 per 100 m in a roadkill hotspot in southwestern Texas. Extrapolations of Central Funnel roadkill based on survey data and road types were 3.6 and 1.1 million in 2016 and 2017, respectively. Spatial distribution of roadkill across the Central Funnel was projected from Texas survey data using 30 m resolution MaxEnt niche models. Highest roadkill probability was linked to arid climate and low human population density. The latter variables may not be directly related to roadkill, but instead represent indirect correlates of increased densities of monarchs where the migration corridor narrows southwards. The higher roadkill projected in southwest Texas and Mexico by MaxEnt models agrees with previously reported monarch roadkill hotspots. MaxEnt-based 2016–2017 projections for annual roadkill rates throughout the Central Funnel averaged 2.1 million. This figure is similar to the result by simple extrapolation, and represents about 3% of the overwintering monarch population for these years. Mitigation at roadkill hotspots in the Central Funnel could reduce monarch roadkill mortality during migration and contribute towards conservation efforts for the monarch butterfly.

Influence of Landscape Factors on Amphibian Roadkills at the National Level

Roads exert multiple effects on wildlife, from animal mortality, habitat and population fragmentation, to modification of animal reproductive behaviour. Amphibians are the most frequently road-killed animal group. Many studies have attempted to analyse the factors driving amphibian casualties on roads, but these factors are limited to the roads themselves (e.g., traffic, type of roads, roads crossing water bodies) or to structures along them (e.g., ditches, walls). Sometimes, roadkills are related to land use along the roads. We analysed the influence of landscape factors on roadkill hotspots at the national level (Slovenia). Specifically, we aimed at: (1) identifying hotspots of roadkills, (2) analysing whether records of amphibian presence on roads are related to the distribution of water bodies and (3) analysing which factors (proximity to water bodies or human factors) explain the distribution of hotspots. Hotspots were identified by Malo’s method. Roadkills were modelled with Maxent for the first time in Slovenia. The relationships between amphibian presence and hotspots with factors were analysed with GLM. A total of 237 road sections were identified as hotspots, corresponding to 8% of road sections and containing 90% of road-killed individuals. Proximity to forests, meadows and agricultural land were the most important variables in Maxent models. The number of roadkills depended on the proximity to agricultural land, forests, water bodies and wetland areas, while the number of hotspots additionally depended on the proximity to urban settlements.

Roadkill mitigation: trialing virtual fence devices on the west coast of Tasmania

Wildlife roadkill is a worldwide issue being tackled using several mitigation methods that have variable efficacy. Tasmania has a significant roadkill issue, and several endemic species that are vulnerable to roadkill. Virtual fence devices are manufactured in Austria and were originally designed to mitigate against the impact of vehicles hitting large game species such as deer and boar. Here, we trial the devices over three years at a single site in Tasmania to determine whether they are effective in reducing roadkill of Tasmanian mammal species. While there was no spatial replication in this trial, a reduction in total roadkill rate, and in the most commonly affected species, by 50% suggests that these devices have enormous potential to substantially reduce roadkill rates. Many unique mammal species no longer found in the wild on mainland Australia are still found in Tasmania, making mitigating roadkill hotspots an important conservation tool to help maintain presence of these species in their last remaining stronghold. Road managers, including councils, in other Australian States that suffer from high rates of wildlife roadkill may benefit from the knowledge of the results of this trial.

GDefrag: A graph-based tool to help defragmenting landscapes divided by linear infrastructures

Habitat fragmentation is a major biodiversity threat. Linear infrastructures (e.g. roads) hamper the movement of individuals and cause non-natural mortality. Roadkill hotspots have been used to define priority areas for road effect mitigation, but data availability and reliability is an issue, particularly on wide spatial scales. Additionally, mitigating the whole infrastructure network is unfeasible. Expedite methods are required to address such challenges. We present the gDefrag package, a graph-based approach that builds on habitat value and accessibility after simplifying the landscape as a graph. Its advantages include not requiring roadkill or movement data, and providing effective methods to deliver reliable information, allowing landscape managers to address landscape fragmentation overall. gDefrag prioritizes roads which should be targeted first to defragment the landscape. The software includes a user-friendly manual and currently implements four prioritization criteria: habitat quality, maximum number of inter-habitat paths, overall landscape connectivity, and simultaneously larger and higher-quality habitats.

Daytime driving decreases amphibian roadkill.

Roadkill has gradually become a common factor that has contributed to the decline of amphibians, and traffic volume is an important parameter that can be used to determine the impacts of roads. However, few researchers have studied the effects of either daily or nightly traffic volume on amphibian roadkill in China. Hence, as an essential step for implementing mitigation measures, we conducted 77 road surveys along 10 km of road in the Wanglang National Nature Reserve (NNR) to determine the temporal and spatial distribution patterns of amphibian road mortality. In total, 298 dead individuals (Bufo andrewsi and Rana chensinensis) were observed on the road from April to October in 2017 and during June and August in 2015 and 2016. B. andrewsi had the highest number of records (85.2%) and was more vulnerable to road mortality than R. chensinensis. Amphibian fatalities mainly occurred during the breeding season in April, but there was an additional concentration of B. andrewsi roadkill in June and July. There was a significantly positive correlation between amphibian road mortality and mean night-time traffic volume. Roadkill hotspots were non-randomly distributed throughout the study area and were mainly concentrated in the road sections near the breeding pools. Therefore, to effectively mitigate the effects of road mortality in the Wanglang NNR, measures should be implemented both during hot moments and at hotspots. First, based on roadkill hot moments, during the breeding season (in April) and in June and July, the Wanglang NNR should establish temporary traffic restraints at night. Second, based on roadkill hotspots, culverts should be established in areas near breeding pools adjacent to roads, and barrier walls should be installed to guide amphibians into the culverts.