Roadkill Rates Research Articles

Temporal patterns and factors influencing vertebrate roadkill in China

There have been few studies of vertebrate roadkill in China, and the lack of long-term, large-scale, and multiple-species monitoring and data have made it difficult for transportation departments to make science-based decisions. The 13 highways in the Changbai Mountains of northeast China were selected for 13 years of monitoring. The results showed that there were a total of 13, 309 vertebrate roadkill belonging to 91 species with a roadkill rate of 6.35 ± 2.41 per 100 km per day. The vertebrate roadkill rate recorded on walking and cycling surveys was 8.4 times higher than that of driving surveys. We estimate the roadkill number of the Changbai Mountain area will reach 37,120 ± 14,100 by 2030. Our findings provide a theoretical basis for proposing roadkill mitigation measures, and also provide a baseline for comparison with future roadkill monitoring results in Changbai Mountain area.

Road Permeability Index as a tool for mitigation planning of road impacts on wildlife in Colombia: a case study using mammals

Mitigation planning for road projects in Colombia has been largely based on actions aimed at reducing wildlife roadkills. Nonetheless, the efficiency of these actions is compromised because of the absence of robust empirical studies supporting their implementation. In this work, I used the Road Permeability Index (RPI) in conjunction with expert knowledge information to estimate the strength of the barrier effect imposed by an under-construction road (Yuma road, Santander department, Colombia) on nine functional groups of medium and large-sized mammals. The influence of 12 landscape variables on the permeability of each functional group was assessed at 30 locations along the road. The RPI was calculated for each functional group, and the whole studied mammal assemblage at each location. The relative influence of each variable on overall permeability was also estimated. I found that functional groups including terrestrial and semiarboreal species present higher contribution values to overall road permeability, indicating that they represent priority targets for mitigation actions. The RPI identified six highly permeable locations for animal movement—where higher roadkill rates are expected—which are key for implementing mitigation strategies aimed at reducing wildlife road mortality. Forest cover had the strongest influence on road permeability, therefore is crucial for landscape conectivity. Overall, the results of this work show that RPI constitutes a reliable and easily adaptable alternative for identifying priority species, or faunal groups, and locations for road mitigation planning.

Assessing the impact of roadkill on the persistence of wildlife populations: A case study on the giant anteater

Human activity is depleting biodiversity, and road networks are directly contributing to this trend due to roadkill. Nevertheless, few studies empirically estimated the impact of roadkill on wildlife populations. We integrated information on roadkill rates, population abundance, and animal movement to estimate the survival rates and the proportion of the population likely to be extirpated due to roadkill, using giant anteater (Myrmecophaga tridactyla) as model species. We then assessed the consequent implications of roadkill on population persistence using population viability analysis (PVA). The yearly survival rate of resident anteaters inhabiting road vicinity areas (0.78; CI: 0.62−0.97) was considerably lower than for those living far from roads (0.95; CI:0.86–1.00). The real number of anteaters being road-killed is considerably higher than the one recorded in previous studies (by a factor of 2.4), with ca. 20% of the population inhabiting road vicinity areas being road-killed every year. According to PVA results, roadkill can greatly affect the persistence of the giant anteater populations by reducing the growth rate down to null or negative values. This study confirms that roads have significant impacts on local population persistence. Such impacts are likely to be common to other large mammals, calling for effective mitigation to reduce roadkill rates.

Roadkill patterns in Latin American birds and mammals

AbstractAimRoads are a major threat for wildlife, degrading habitat and causing mortality via wildlife–vehicle collisions. In Latin America, the conjunction of high biodiversity and a rapidly expanding road network is reason for concern. We introduce an approach that combines species traits and habitat preferences to describe vulnerability and map areas of high roadkill risk. Thus, we present the first assessment of roadkill impacts for Latin American birds and mammals.LocationLatin America.Time period1994–2020.Major taxa studiedBirds and mammals.MethodsWe compiled data from 85 roadkill surveys from Latin America that provided 1,691 roadkill rate estimates for 346 bird and 159 mammalian species, from which 520 rates from 249 birds and 457 rates from 103 mammals were used for analyses. We applied random forest models to predict observed roadkill rates considering species traits, habitat preferences and the geographical coordinates of each study to control for local and regional variation. Fitted models were used to predict spatial risks on Latin American roads for roadkilled birds and mammals across their areas of habitat.ResultsWe found higher roadkill rates for larger birds and medium‐sized mammals with faster reproduction (more clutches/litters per year and early maturity ages), higher population densities and wider use of habitats that included anthropized areas. In mammals, scavengers and those with diets based on invertebrates showed higher rates. Spatial predictions revealed higher rates on roads across Central America, northern Andean regions, eastern Brazil, Uruguay, central and eastern Argentina and southern Chile.Main conclusionsThis first comprehensive assessment for Latin America explores various drivers of roadkill risk for birds and mammals and identifies species and areas where existing roads can impact wildlife. Trait‐based models fine‐tuned with realistic spatial information that accounts for habitat suitability provide a valuable tool for the assessment of human impacts, including roads and traffic.

Spatial and temporal distribution of bat mortality on a highway in southeast Brazil

Roads and highways can work as barriers to the movement of many species, thereby preventing the individuals from accessing feeding and reproduction sites and the immediate risk of colliding wild species with vehicles. Identifying the impacts of roads on wildlife can contribute to the establishment of actions that promote conservation. In Brazil, data on collisions between bats and vehicles are scarce and underestimated in the literature. We described bat roadkill from 2008 to 2019 on a stretch of the BR-040 highway, which crosses an area of Atlantic Forest. Roadkill species were identified and the sites with high collision frequencies were characterized. A total of 923 individuals of 57 species and five families of chiropterans were identified. Frugivore bats showed the largest number of affected individuals, with Artibeus lituratus, a common species in the study region, with the highest number of roadkills. The diet and foraging behaviour were the most likely factors explaining most of the bats killed on the highway. The highest roadkill rate was documented in the fall, and the critical points located nearby the APA Petrópolis and REBIO of Tinguá, environmental protection areas. We reinforce the need to mitigate these roadkills, ensuring that road systems, which constitute municipal, state and federal highways, are built to prevent major disturbance of habitat and displacement routes of these species. We believe in the need for mitigations, and considering the various species involved, we suggest speed bumps construction reducing the speed limit, installing bridges, and signaling the presence of wildlife, before the stretches identified as hotspots.

Roadkill mortality decreases after road inauguration

The main factors affecting specific road casualty rates are related to life-history traits, road features, and landscape variables. After road inauguration, roadkill rate and spatial and temporal patterns can change substantially due to changes in traffic intensity, avoidance behaviour or local population decline. Despite the Canary Islands constituting a biodiversity hotspot, Canarian ecosystems are highly threatened because of the high human density, and studies on anthropogenic sources of mortality of wildlife are scarce. Here, we counted roadkills during two annual cycles after the inauguration of an 8.8-km-road section on Tenerife, the largest and most densely populated island of the Canaries. We counted 694 roadkills belonging to a minimum of 19 species of birds and six species of introduced mammals. Seasonal variation was apparent during both annual cycles, particularly for birds, being the majority of victims concentrated in May and June. Although traffic intensity increased since road inauguration, the number of roadkills decreased significantly in the second annual cycle. The reduction in road mortality in the second cycle could be related to some non-mutually exclusive factors such as population decline, road avoidance, or weather conditions. As road networks of the Canary Islands are still increasing, further studies quantifying road mortality impacts on Canarian ecosystems and threatened species are urgently needed to guarantee the management and conservation of its fragile wildlife.

Evaluating impacts of road expansion on porcupines in a biodiversity hotspot

The improvement of transportation networks by road twinning is a major trend worldwide, but also brings possible threats to wildlife that have not been thoroughly assessed. The present study aims to evaluate how the changes in structural characteristics during road twinning affect roadkill rates of dwarf hairy porcupines ( Coendou spinosus ) in the southeast portion of the Brazilian Atlantic Forest, a major world biodiversity hotspot. The dataset for this study comes from monthly monitoring campaigns, carried out between 2013 and 2018, in the BR-101/RJ Norte (km 84–124), a major highway located in Rio de Janeiro state. The influences of structural modifications by road twinning (number of lanes, presence of road barrier, traffic, presence of construction operations, number of native vegetation on both margins of the road, sampling period) in the species roadkill rates were evaluated by means of generalized linear mixed effects models (GLMMs) selected based on an information theoretical approach. The average roadkill rate was 0.015 porcupine individuals/km/day of sampling and presented a trend of increase during the expansion works and decrease after the conclusion of road twinning and lane widening. Model averaging showed that presence of Jersey barriers, number of lanes, construction works for twinning, and traffic were the most influential variables for roadkill rate. An emergency measure to minimize the impact of Jersey barriers could be the implementation of escape mechanisms alongside Jersey blocks that could enable animals to cross the divider. We also propose other mitigation measures, such as the installation protective fences and safe passages, and draw insights into the behavioural responses of porcupines to roads and traffic.

Analysis of Wildlife Roadkill in a Road Circuit. Case study of a Colombian road in the Department of Huila: Neiva - Rivera - Campoalegre

This research contributes information related to records of wildlife roadkill in the different roads of the department of Huila. The results come from samplings carried out during the rainy season from October to December of 2017 on the Neiva - Rivera - Campoalegre road circuit. The highest roadkill rate was recorded in section 1, Neiva - Rivera (Los Cauchos tollbooth); which had high traffic flow during the day (5045 vehicles/month), high speed limit (90 km / h), and an arboreal coverage that forms a green tunnel due to the lack of lighting on this road.
 A total of 102 dead specimens were registered in this case study; predominantly mammals (53 specimens, 51.96%) and the species Didelphis marsupialis (48, 47.06%), followed by reptiles (34, 33.33%) whose most affected species were the Boa constrictor (9, 8.82%) and the Iguana iguana (7, 6.86%). Additionally, birds were the third most affected group (12, 11.76%) classified in 8 species, such as the Megascops choliba which was the most affected (4, 3.92%). Amphibians were the least affected group (3, 2.94%), mainly the Rhinella horribilis species (2, 1.96%).

Does wildlife crossing infrastructure work? A case study of three canopy-bridge designs and exclusion fencing from Moreton Bay Regional Council, Queensland

Although fauna crossing structures have been installed throughout the world, most studies have been of underpasses and overpasses. Canopy-bridges, however, have received much less attention. In addition, although exclusion fencing is used extensively, its effectiveness has rarely been assessed. Since 2015, Moreton Bay Regional Council (MBRC), in southern Queensland, Australia, has installed various mitigation structures at 21 sites. This study compared the use of different designs of canopy-bridge and assessed the effectiveness of exclusion fencing via camera monitoring and roadkill records. A total of 3151 detections of five arboreal species were made on the canopy-bridges at an average of 0.51 crossings per day for both rope cages and rope ladders and 0.64 on rope cages and 0.77 on rope ladders when a poorly used bridge of each type was excluded. A single aluminium ladder had 33 crossings (0.15 crossings per day) but was available for only a short time. Roadkill rates of all species declined by 84% at sites with underpasses and fencing compared to 93% at sites without, but only 39% at control sites. This may be due to the canopy-bridges or the addition of complementary infrastructure, such as signage, pavement stencilling and driver awareness.

WILDLIFE ROADKILL IN THE SURROUNDINGS OF EMAS NATIONAL PARK, CERRADO BIOME, BRAZIL

Roadkill is a serious threat to biodiversity conservation especially when roads are near natural habitats of wildlife, such as the Emas National Park (ENP), a Protected Area in Mid-west Brazil in the Cerrado Biome. We aimed to identify the species killed on a stretch of the GO-341 highway that is tangent to the ENP. We investigated if roadkills were influenced by seasonality, sugar cane harvest and by the activity pattern of the animals (diurnal/nocturnal). We also analyzed if roadkills were aggregated in space, where the roadkill hotspots were located, if they were influenced by seasonality, and if they were different for the most abundant species. The highway was monitored with a vehicle, in the morning, at a speed of 40 to 60 km/hour, daily, with two observers. We covered a total of 4,230 km during the 90-day monitoring period, which included dry and rainy seasons. We recorded 132 wild animals’ roadkills: 67 birds (51 %), 60 mammals (45 %) and 5 reptiles (4 %). We identified 22 vertebrate species, including 13 birds, six mammals and three reptiles. The roadkill rate was 0.03 animals/km/day. During the dry season, the blue-and-yellow macaw (Ara ararauna) had higher roadkill rates. The crab-eating fox (Cerdocyon thous) was the only species with higher roadkill rates during the sugarcane harvest. Most birds killed had diurnal habits, for mammals, no difference was observed concerning the activity pattern. Bird roadkills were aggregated considering the entire data set, as well as for the dry and rainy seasons separately. Mammal roadkills were aggregated only when considering the entire data set. The location of bird roadkill hotspots differed between seasons. The roadkill hotspot location of birds and mammals highly overlapped those observed for the two most abundant species of these taxa, respectively, Ara ararauna and Euphractus sexcinctus.

Assessing the Relative Impacts of Roadkill and Nest Poaching on the Population Viability of the Blue-and-Yellow Macaw, Ara ararauna (Aves: Psittaciformes), in a Brazilian National Park

The blue-and-yellow macaw (Ara ararauna) is suffering from higher roadkill rates (RK) at the Emas National Park (ENP), an important Brazilian National Park in the Cerrado biome. This species is also a victim of nest poaching for illegal trade. We modeled the blue-and-yellow macaw population’s viability in ENP and how this viability is affected by roadkill and nest poaching. We hereby report that the species is critically at risk and could be extinct in about a decade when considering both threats. Without considering any threat, 150 individuals are necessary to maintain a viable population. When individuals are harvested at a roadkill rate of 0.008 individuals/km/year and at twice this level, the viability figures increase to 4500 and 7500 birds, respectively. For nest poaching, we estimated that 2000 individuals are required to maintain a viable population. When both threats are present, 5000 individuals are necessary. The dynamics of the population are highly sensitive to the age at which females reproduce for the first time and the proportion of reproducing adult females, followed by the rate of adult survival. Our model demonstrates how even a non-threatened highly mobile species, such as the blue-and-yellow macaw, may be at risk due to human activities.

Can virtual fences reduce wombat road mortalities?

Roadkill is a worldwide issue that can cause local population extinctions. In Australia numerous species are affected, however the bare-nosed wombat (Vombatus ursinus) is particularly vulnerable due to its preference for disturbed habitats. Collisions with motor vehicles causes significant damage to the vehicle and sometimes the driver, as well as wounding or killing the wombat. Virtual fences are light and sound-based devices, originally developed in Austria that can be used to reduce roadkill through mitigation. They have had mixed results. In this study a virtual fence was installed along a 1.5 km stretch of road in semi-rural NSW, Australia, with the aim of reducing wombat roadkill through the use of this form of mitigation strategy. The number of roadkilled wombats was counted before and after the fence was installed in March 2020. Prior to the fence being installed 23 wombats were killed and after the fence was installed six wombats were killed. Along Old Bega Road, outside of the fenced area 64 wombats were killed pre-fence installation and 17 post fence installation. Bare-nosed wombats are semi-fossorial ecosystem engineers with an important role in the ecosystem and despite being listed as Least Concern are readily impacted by roadkill. Virtual fencing implemented in regions that have high wombat roadkill rates may aid in reducing road deaths and species conservation. However, we recommend that more research is required to assess virtual fencing, as a roadkill mitigation strategy, including an investigation into a larger number of species in a range of different habitats.

Geography of roadkills within the Tropical Andes Biodiversity Hotspot: Poorly known vertebrates are part of the toll

AbstractWe explore the effect of roads in animal mortality within the Biodiversity Hotspot with the highest number of endemic species of vertebrates on Earth, the Tropical Andes. Our objectives were to know which species are killed on roads in this particularly biodiversity‐rich area and how landscape composition and configuration influences roadkills. We systematically looked for roadkills along roads that border three protected areas in the Ecuadorian Andes. To evaluate our hypotheses, we used correlation, logistic regression, and GIS analyses. We surveyed a total of 7128 km and observed a roadkill rate of 6.24 (95% CI = 5.35–7.14) individuals per 100 km/day. Roadkills included poorly known endemic and endangered vertebrates; among them, one undescribed snake species of the genus Atractus. Most roadkills were by pastures, the dominant vegetation by roads in our study area. Roadkills were more likely to occur near bridges and were more frequent at greater distances from natural vegetation, towns, and rivers. We conclude that pastures and bridges may be functioning as ecological traps for small and poorly known vertebrates. Mitigation measures could include increasing road permeability to wildlife by constructing culverts in critical points where mortality is high, and the adaptation of areas beneath bridges for them to function effectively as wildlife underpasses. These measures should be complemented with fences to exclude vertebrates from roads in areas near wildlife passages and along pastures. We encourage the development of similar studies in biodiversity‐rich areas to inform mitigation measures that can be adapted to local conditions.Abstract in Spanish is available with online material.

Factors influencing bat road casualties in a Neotropical savanna

Collision with vehicles is one of the main causes of death for many vertebrates; however, little is known about bat roadkill. Thus, in this study we described bat roadkill in an area of Neotropical savanna and evaluated factors potentially affecting its occurrence. We surveyed 114km of roads on the margins of protected areas in the Brazilian Federal District for 5 years. We analysed bat roadkill on three types of roads (dirt roads, two-lane paved highways, and four-lane paved highways) and recorded distance from water and presence of artificial light. Bat roadkill was calculated for 2-km sections and analysed using generalized linear mixed models (GLMMs) with the following independent variables: season, road type, presence of light, and distance from water. We used section nested within road as a random effect. We estimated a total of 4740 roadkilled bats and identified individuals from three families. Bat road casualties were more numerous in the rainy season and on four-lane highways, whereas proximity to water and presence of artificial light were not related to roadkill number. The higher roadkill rate during the rainy season may be explained by higher bat activity due to the increased availability of resources. Regarding the influence of road type, four-lane highways have the highest traffic volumes in the area and the highest speed limits, which are associated with higher roadkill rates. Bats represent the most diverse order of mammals in the Cerrado, where they provide many important ecological services, which need to be preserved.

DON'T SPEED UP, SPEED KILLS: MAMMAL ROADKILLS ON HIGHWAY SECTIONS OF PR-445 IN THE SOUTH OF BRAZIL

Animal-vehicle collisions are the main negative impact of roads on wildlife, where they cause population declines, shifts in community structure, and potential changes in species behavior. Here, we determined mammal roadkill rates and the hotspots with higher rates for medium- and large-bodied mammals on the Highway PR-445 in the state of Paraná, Brazil. We have also evaluated possible differences in the frequency of roadkills concerning species activity patterns and their feeding habits. In doing so, we monitored the PR-445 twice a week between the kilometers 1 and 76, from March 2018 to March 2019, totaling 7296 km after 96 trips. We have recorded 93 mammal roadkills belonging to 17 species, representing a rate of 0.013 individual/km/day. The Carnivora, Didelphimorphia, and Cingulata orders showed to be the most common representatives among the roadkills. Omnivores were more prone to get hit by vehicles than herbivores and carnivores. The type of mammal activity pattern was not determinant in explaining the differences in roadkill rates. Highways in Paraná are among the roads that register the highest number of vehicle collisions with vertebrates in the country. This issue, together with extensive habitat loss and fragmentation, increases the threats to the relictual fauna. Our results indicate that the regions with the highest incidence of mammal roadkills on PR-445 are those close to stretches over rivers and with remnants of native vegetation. Thus, we emphasize that more comprehensive measures (e.g., wildlife passages and speed reducers) are essential to mitigate the impact of roads on wildlife.

Where wildlife and traffic collide: Roadkill rates change through time in a wildlife-tourism hotspot

Understanding when and where roadkill is most likely to occur is vital to reducing wildlife-vehicle collisions. However, little is known about how roadkill rates change through time and whether or not the key influences on roadkill also change. Understanding changes in roadkill will facilitate the best implementation of mitigation measures. We aimed to determine how roadkill rates have changed between two distinct time periods and assess whether the spatial and temporal drivers of roadkill rates may have changed: with a view to informing taxon-specific mitigation strategies. We assess the spatial and temporal factors that influence road mortalities in two periods (1998–1999 and 2014) at the same site for multiple taxa. Bi-weekly surveys were undertaken from February to May 1998 and 1999 and again from February to June 2014. In total 2479 individual roadkill were recorded throughout the surveys, with 1.59 roadkill per km per month in the 1990s, increasing to 2.39 per km per month in 2014. Roadkill rates increased primarily with road speed limit with mortalities peaking at moderate (60–80 km/h) speeds, however, the structural complexity of roadside vegetation influenced roadkill rates for some taxa but not others. We show that roadkill rates have changed through time with shifts in both the temporal and spatial influences on these roadkill rates. These changes are likely associated with changes in the abundance of taxa and increased vehicle traffic. The spatial and temporal drivers of roadkill rates were found to be taxon specific, and although mitigation measures exist, assessment of their efficacy remains a priority.

Avian roadkills occur regardless of bird evolutionary uniqueness across Europe

Through an extensive literature review and using a large dataset collected from several European studies, we explored the frequency of occurrence of road bird casualties. First, we modelled the inter-specific variation in roadkill’ frequency across the avian phylogeny, testing for phylogenetic signal. Then, we explored the association between frequency of roadkill and some avian traits and evolutionary distinctiveness score of species.The rate of roadkill did not show a phylogenetic signal, indicating that the incidence of avian casualties is independent of the phylogenetic position of species. The incidence of roadkill was unrelated to the evolutionary distinctiveness, distribution range size, type of diet, or period of activity of species, but was slightly negatively associated with the species’ body mass. This result implies that roadkill is a form of anthropogenic mortality widely generalized concerning avian phylogeny. We highlight that roadkill mitigation measures could benefit from incorporating peculiarities of local or regional avifauna.

Roadkill risk and population vulnerability in European birds and mammals

Roads represent a threat to biodiversity, primarily through increased mortality from collisions with vehicles. Although estimating roadkill rates is an important first step, how roads affect long‐term population persistence must also be assessed. We developed a trait‐based model to predict roadkill rates for terrestrial bird and mammalian species in Europe and used a generalized population model to estimate their long‐term vulnerability to road mortality. We found that ~194 million birds and ~29 million mammals may be killed each year on European roads. The species that were predicted to experience the highest mortality rates due to roads were not necessarily the same as those whose long‐term persistence was most vulnerable to road mortality. When evaluating which species or areas could be most affected by road development projects, failure to consider how roadkill affects populations may result in misidentifying appropriate targets for mitigation.

Mortalidad de serpientes en la vía El valle de Toledo-Toledo, Antioquia –Colombia

A través de 4 meses de muestreo continúo comprendidos entre el 1 octubre de 2018 y 31 de enero de 2019, se determinó la mortalidad de serpientes causada por el tránsito vehicular en un segmento de 17 km de la vía entre El Valle de Toledo y el municipio de Toledo, departamento de Antioquia, Colombia. Se registraron 18 individuos correspondientes a 14 especies y tres familias, siendo Colubridae la más representativa (12 spp.), y Mastigodryas pleei y Leptophis ahaetulla las especies más atropelladas. Se obtuvo una tasa de atropellamiento (TA) de 0.0043 individuos/km, la cual es relativamente baja al compararla con las obtenidas en otros estudios relacionados. El 50% de los registros ocurrieron en el mes de enero, época de menor precipitación en la zona de estudio. Finalmente, estos resultados muestran una pequeña parte de la afectación vehicular sobre este grupo de fauna, que podría tener mayor impacto hacia el futuro de acuerdo con el desarrollo de la infraestructura vial de la región, para lo cual se proponen algunas estrategias que permitan mitigar los efectos negativos sobre la fauna.

Roadkill of medium to large mammals along a Brazilian road (BR-262) in Southeastern Brazil: spatial distribution and seasonal variation

ABSTRACT Like all human action that changes ecosystems, roads contribute to habitat fragmentation, acting as barriers and, consequently, causing biodiversity loss. Given the need for studies related to roadkill of wild animals, especially in the Atlantic Forest, and the vulnerability of mammal species to roadkill on the roads, we analyzed roadkill data of medium and large mammals. The study was carried out in a 100 km stretch of the BR-262 road, Atlantic Forest biome, in the Espírito Santo state. We obtained roadkill mammals’ carcasses by 42 monitoring campaigns, between January 2017 and January 2018. We recorded 259 carcasses of 22 species, which resulted in a roadkill rate of 0.062 mammal/km/day. We found that roadkill rates are higher in rainy months and lower in dry ones. We found support that three variables best predicted roadkill occurrence in the BR-262 road (i.e. positive relationship with forest cover, and accumulated precipitation ‘rainfall’, and negative relationship with speed reducers). These results indicate an alarming impact on the mammalian fauna at the site and reinforce the need for management measures and actions to reduce the mortality of wild mammals on the roads.