Road Mortality Research Articles

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.

Predicting spatiotemporal patterns of road mortality for medium-large mammals

We modelled the spatiotemporal patterns of road mortality for seven medium-large mammals, using a roadkill dataset from Mato Grosso do Sul, Brazil (800 km of roads surveyed every two weeks, for two years). We related roadkill presence-absence along the road sections (1000 m) and across the survey dates with a collection of environmental variables, including land cover, forest cover, distance to rivers, temperature, precipitation and vegetation productivity. We further included two variables aiming to reflect the intrinsic spatial and temporal roadkill risk. Environmental variables were obtained through remote sensing and weather stations, allowing the estimate of the roadkill risk for the entire surveyed roads and survey periods. Overall, the models could explain a small fraction of the spatiotemporal patterns of roadkills (<0.23), probably due to species being habitat generalists, but still had reasonable discrimination power (AUC averaging 0.70 ± 0.07). The intrinsic spatial and temporal roadkill risk were the most important variables, followed by land cover, climate and NDVI. We show that identifying spatiotemporal roadkill patterns may provide valuable information to define specific management actions focused on road sections and time periods, in complement to permanent road mitigation measures. Our approach thus offers a new insight into the understanding of road effects and how to plan and strategize monitoring and mitigation.

Fine-scale determinants of vertebrate roadkills across a biodiversity hotspot in Southern Spain

An increasing number of wildlife-vehicle collisions occur each year worldwide, which involves extensive economic costs and constitutes one of the main anthropogenic causes of animal mortality. Because of this, there is an urgent need to identify the factors leading to collision hotspots and thus implementing effective mitigation measures. By using a stratified random sampling survey, we investigated the fine-scale determinants of roadkill probability in small and medium-sized birds and mammals across a country-size region of Southern Spain, Andalusia (87,000 km2), located within a global biodiversity hotspot. During two consecutive seasons, we regularly surveyed 45 road transects of 10 km each and characterized the site-specific attributes of both roadkill and random points, including traffic density, road design (embankments, medians, fences, roadside vegetation and distance to curves), and adjacent landscape matrix. Based on this information, we investigated variation in collision risk according to landscape and road features, and the life history of the affected taxa. Mortality rates of mammals and birds increased with traffic density, and were also significantly affected by the distance to the nearest curve, slope of embankments, height of roadside vegetation, and land use adjacent to roads. Road mortality of both birds and mammals was related to the presence and typology of fences and center medians, so more densely vegetated medians and smaller mesh sizes reduced roadkill probability. Overall, our results indicate that roadkill risk may vary at exceedingly small spatial scales. The information provided by this extensive survey may be used to identify taxa-specific factors associated to roadkill risk and priority points for action. Our findings will therefore be relevant for the design of safer roads for both drivers and wildlife through the application of effective mitigation measures.

Factors influencing predator roadkills: The availability of prey in road verges

Road mortality is the most noticeable effect of roads on wildlife. Road verges may provide important refuges for small mammals and rabbits, particularly when roads cross intensive agricultural or grazed areas. In these circumstances, the increasing use of verges by prey species may attract predators to road surroundings increasing the risk of roadkill. The aim of this study was to quantify the role of prey availability (small mammals and rabbits) on predator road casualties, taking into account road and surrounding landscape characteristics. We analyzed this effect on different predator species, such as, snakes, owls and mammal carnivores. The study took place in a 10 km stretch of a National Road (EN4) in southern Portugal. Relationships among predator mortality and explanatory variables (prey abundance, landscape characteristics, and road verge features) were evaluated using Multivariate Redundancy Analysis (RDA) followed by a variation partitioning. Our results show that, although landscape features explained most of the mortality variation, the prey availability was also very important. Roadkills of Montpellier snake and Egyptian mongoose are strongly associated with wild rabbit abundance on verges, while mortality of stone marten, barn owl and tawny owl is related with wood mouse abundance, Mediterranean forest (montado) density, and verge shrub density. Implications for verge management and implementation of mitigation actions are discussed. We suggest vegetation removal in verges to decrease shelter and food availability for prey, and/or the promotion of habitat for prey in areas distant from roads.

Road mortality of freshwater turtles in Palawan, Philippines

The impact of road mortality on freshwater turtle populations on a global scale could be significant enough to cause the extinction of sensitive species. Essential data on roadkill abundance, composition, spatial patterns, and temporal distribution is needed for crafting mitigation strategies. To provide such information, a survey was conducted along the highway section (67 km) connecting Aborlan and Puerto Princesa City in Palawan, Philippines. Collection of data was done four times a month from January 2010 to December 2015. A total of 127 road-killed turtles belonging to two species of the Geoemydidae family were recorded, 102 (80.3%) of which were classified as the Southeast Asian Box Turtle (Cuora amboinensis) and 25 (19.7%) were identified as the Asian Leaf Turtle (Cyclemys dentata). The increase in road traffic noticed during the survey period possibly caused the corresponding increase in the roadkill counts of C. amboinensis, which is a more common species. Concurrently, the decline in the road-kill counts of C. dentata may indicate a severe drop in the population of this less common species. Roadside habitat types, time of the day, and presence of water bodies are found to be important predictors of road-killed turtles. High densities of road-killed turtles clustered in short segments of the road which identified as hotspots. Effective mitigating measures to curve down the impact of road mortality on turtle populations must be implemented and focusing the conservation strategies along the hotspots is considered an efficient and practical option.

Investigation on the road mortality of Anuran species on the Ikorodu-Epe/Ejirin-Ijebu Ode Roads in Lagos and Ogun States, Nigeria

The effect of road kills of anuran species by vehicular traffic on the Ikorodu-Epe/Ejirin-Ijebu Ode road in Lagos and Ogun States was investigated. The mean traffic density on the road during the survey (between 18:30-20:30hr and 06:00 and 07:00hr) was 127±45 vehicles/hr, which ranged between 72 and 216 vehicles/hr. A total of 738 anuran road mortalities among eight species were recorded [661 (89.6%) were identifiable, while 77 (10.4%) were not]. Ptychadena pumilio had the highest mortality of 67±27.1 individuals, while Xenopus muelleri and Aubria subsigillata were the least susceptible to road kills. This respectively represented 2.66±1.5 and 2.66±3 individuals each. Most mortality (256 individuals) occurred on the section of the road bordered by grassland/tertiary vegetation. However there was no significant difference (at P&gt; 0.05) between the anurans killed along the different vegetation structures bordering the road (F2,21 = 0.415). About 473 live anurans belonging to five species were observed of which P. pumilio, the highest constituted the greatest number (81±42.9), while the least Hoplobatrachus occipitalis 7.3±4.2 was recorded. Both species had greater live counts than road kills compared to other anuran species that had greater road kills than live counts recorded. The greatest number of live anurans was recorded at where grassland/tertiaryvegetation occurred. This constituted a total of 198 individuals (41.8%), while the least occurred at the secondary/primaryvegetation which had 95 individuals (20%). However, the difference was not significant (F2,12 = 0.600) at P&gt; 0.05. It is evident that anuran migration is an integral part of their biological activity. However vehicular traffic sadly possesses a negative effect on this activity. Precautionary measures are necessary to reduce population decline and possible extinction of not only the anuran species but also other wildlife species, which is a positive direction in the conservation of biological diversity. Keywords: Vehicular traffic, anuran, mortality, vegetation, road kill, conservation

Weevils Die in Vain? Understanding Messages from Road-Killed Weevils (Coleoptera: Curculionoidea)

Road mortality has a negative impact on numerous animals with conservation importance, including invertebrates. Some weevils are considered pest insects, thus there is little concern when they fall victim to road traffic. Nevertheless, information offered by road-killed weevils can be of conservation, biological, or zoogeographic value. To understand this information, during 2015 and 2016 we collected 186 road-killed weevils belonging to 23 species from secondary roads with low traffic in eight regions of Romania. As for other animal groups, weevil road mortality is influenced by the habitat surrounding the road and the time of year. The highest number of road-killed weevil species was recorded on roads surrounded by sandy areas. In areas surrounded by forests, the number of road-killed species was low, but the Shannon-Wiever diversity index was high, and some species were present only in these regions. The highest numbers of weevils were killed by cars in the spring. Some road-killed species are first records for the region they were identified in, others are rare in Romania. The mountain species Donus oxalis (Herbst, 1795) was encountered at just 80 m altitude in the Danube Gorge.

The relationship between impact speed and the probability of pedestrian fatality during a vehicle-pedestrian crash: A systematic review and meta-analysis

BackgroundPedestrians struck in motorised vehicle crashes constitute the largest group of traffic fatalities worldwide. Excessive speed is the primary contributory factor in such crashes. The relationship between estimated impact speed and the risk of a pedestrian fatality has generated much debate concerning what should be a safe maximum speed limit for vehicles in high pedestrian active areas. MethodsFour electronic databases (MEDLINE, EMBASE, COMPENDEX, and SCOPUS) were searched to identify relevant studies. Records were assessed, and data retrieved independently by two authors in adherence with the PRISMA statement. The included studies reported data on pedestrian fatalities from motorised vehicle crashes with known estimated impact speed. Summary odds ratios (OR) were obtained using meta-regression models. Time trends and publication bias were assessed. ResultsFifty-five studies were identified for a full-text assessment, 27 met inclusion criteria, and 20 were included in a meta-analysis. The analyses found that when the estimated impact speed increases by 1 km/h, the odds of a pedestrian fatality increases on average by 11% (OR = 1.11, 95% CI: 1.10–1.12). The risk of a fatality reaches 5% at an estimated impact speed of 30 km/h, 10% at 37 km/h, 50% at 59 km/h, 75% at 69 km/h and 90% at 80 km/h. Evidence of publication bias and time trend bias among included studies were found. ConclusionsThe results of the meta-analysis support setting speed limits of 30–40 km/h for high pedestrian active areas. These speed limits are commonly used by best practice countries that have the lowest road fatality rates and that practice a Safe System Approach to road safety.

A turtle population study in an isolated urban wetland complex in Ontario reveals a few surprises

We report on the results of the first mark–recapture survey of freshwater turtles in an isolated urban wetland complex in one of Canada’s fastest growing municipalities. Although we found turtles in every surveyed wetland, the density and assemblage of turtles in smaller wetlands were significantly different than in larger wetland bodies. We also documented two species of turtles that were thought to be absent from this wetland complex, the Northern Map turtle and Eastern Musk turtle. We noted that a wetland that was bisected by a high-traffic road showed a male-skewed sex ratio in the population of Midland Painted turtles but not in the population of Eastern Snapping turtles. As a whole, the sex ratios inside the wetland complex were not skewed. These results reinforce the conclusions of a previous study of a single wetland within this same complex that had found a correlation between road mortality and a male-skewed sex ratio in Midland painted turtles. We discuss population sources and sinks within the complex and the importance of protecting the overland corridors that support the safe turtle movements within this provincially significant wetland complex.

Automated speed control on urban arterial road: An experience from Khon Kaen City, Thailand

The 14 km corridor of the Friendship Highway passing Khon Kaen city, Thailand, was prone to road functionality problems, and high road fatality rates were reported. The local road safety committee, including public and private interdisciplinary parties, recently implemented the automated speed enforcement camera project along this corridor to achieve safer speeds. The objective of this study is to evaluate the efficiency and effectiveness of the implemented project. The results indicated that this project decreased vehicle speed by 9.6% and increased the efficiency of the speed limit enforcement program six to eight times. Accidents, injuries, and fatalities rates decreased by 5.8%, 7.7%, and 34.3%, respectively. These outcomes prove the efficiency of the first stage of this speed control project in the context of developing cities. Further speed management programs are also discussed. The findings would be beneficial for other developing cities whose urban arterial roads encounter traffic accidents that are primarily caused by speeding.

Engaging minibus taxi drivers in the quest for child safer roads

South Africa has double the world average child road fatality rate, with at least 1 300 children killed every year. A leading contributor to this public health challenge is the lack of safe public transport that enables children to reach schools easily. Minibus taxis (MBTs), South Africa’s incarnation of paratransit services, have aimed to fill this gap by providing transport at a reasonably priced fare and a relatively higher frequency, compared with other modes of public transport. However, the informal nature of MBTs means that this form of transport places passengers at a relatively higher risk of road accidents due to the use of unroadworthy vehicles, reckless driving and speeding. This paper provides an overview of the Safe Travel To School (STTS) programme, which was initiated in 2014 with a view to providing a localised intervention that would potentially strengthen the safety of MBTs for scholar transport in South Africa. The programme aims to provide safer travel for child passengers by monitoring driver performance through a tracking device installed in each vehicle and rewarding good driver performance each quarter. A driver recruited into the programme also undergoes health tests and training that covers first aid, defensive driving and road safety training. The literature review that each of these components improves driver performance. A previous evaluation of the programme found that since inception, drivers in the programme have shown better driving performance than general motorists. Thus, the STTS programme potentially provides an implementable practice model for safe scholar transport that is oriented towards a developing country like South Africa.

Factors influencing the spatial patterns of vertebrate roadkill in South Africa: The Greater Mapungubwe Transfrontier Conservation Area as a case study

AbstractFew studies have investigated the factors that influence roadkill occurrence in developing countries. In 2013, we monitored a 100‐km section of the road (comprising the R572 and R521 regional highways and the D2662) that pass through the Greater Mapungubwe Transfrontier Conservation Area in South Africa, to assess the possible factors influencing roadkill. Over a period of 120 days, and across the three ecological seasons, we recorded 981 roadkills (rate = 0.08 roadkill/km/day) from four vertebrate taxonomic groups. We generated predictive models of roadkill from one combined data set that considered eight variables identified from the literature as potential correlates of roadkill. The model that included the distance of the fence from the road, habitat type adjacent to the road, and the presence of a hill in the road (i.e., elevation) or a bank on the side of the road best explained roadkill occurrence. More roadkill was predicted to occur in both open and dense mopane and dense mixed bushveld habitats, on a hill, when there was a bank on the side of the road, and as the distance between the road verge and a fence decreased. Our model provides some insight into the significant predictors of roadkill occurrence and is therefore a valuable tool in identifying sites of high‐potential roadkill frequency and formulating mitigation measures for reducing road mortalities.

Assessing the Impacts of Urbanization on Sex Ratios of Painted Turtles (Chrysemys picta)

Turtles are particularly susceptible to the negative impacts of urbanization due to low mobility and a life history strategy emphasizing long generation times and high adult survival. In addition to declines directly through habitat loss, urbanization has been hypothesized to limit populations of aquatic turtles through changes in population structure, as adult females are disproportionally killed on and near roads, leading to male-biased populations, which can lead to population declines or local extirpations. The purpose of this study was to better understand how urbanization impacts the sex ratios of painted turtles (Chrysemys picta) in an urban ecosystem, as empirical results linking male-biased turtle populations to roads and urbanization are mixed. Using eight years of trapping data from a long-term monitoring program in a suburb of Chicago, IL, USA, we report one of the most male-biased populations ( x ¯ = 75% male) of turtles in the USA, consistent with prevailing road mortality hypotheses. However, we found no evidence that male-biased populations were related to road density or the amount of protected area around a sampling location and found that impervious surface (a metric of urbanization) was weakly related to less male-biased populations. Our results highlight the importance of replicating ecological studies across space and time and the difficulty in assessing population structure in aquatic turtles. We suggest that active conservation measures may be warranted for the continued persistence of urban turtle populations.

An Agent Based Model to Estimate Lynx Dispersal if Re-Introduced to Scotland

Re-introduction of Eurasian Lynx to Scotland is being considered. Work by others has provided an ecological rationale for reintroduction and trial re-introductions are proposed on the Scottish border. This paper presents an Agent Based Model which simulates the potential for individual lynx to successfully disperse from a release point, using movement rules derived from observation of wild lynx in Europe. Results suggest high mortality from road crossings could hinder effective dispersal. The model is used to suggest the strongest candidate release site based on dispersal with and without a road mortality effect. This occurs in the Galloway Forest Park. The model is built using open source tool Netlogo, the programming language is relatively straightforward and extensible so other life events and human interactions can be modelled. Movement parameters can easily be reset to explore other hypothesised movement patterns. This paper contributes to spatio-temporal understanding of lynx dispersal, via a dynamic visual representation of movement in an ABM. This may help appraise the case for re-introduction in a particular location as well as providing a discursive tool that may help to understand and resolve concerns of community stakeholders, which would aid development of suitable policies. Model code is available via online repository: https://github.com/DrIanPhilips/LynxABM.

Safety Culture among Private and Professional Drivers in Norway and Greece: Examining the Influence of National Road Safety Culture

While Norway had the lowest road mortality rate in Europe in 2017, Greece had one of the worst road safety records of all EU-27 countries. The present study investigates road safety culture (RSC) as an explanation for this discrepancy by: (1) Comparing the road safety behaviours among professional and private drivers in Norway and Greece, (2) Examining factors influencing road safety behaviours, focusing especially on national road safety culture, and (3) Examining the influence of road safety behaviours and other factors (e.g., demographic and work-related variables) on accident involvement. This is done by comparing survey answers of private car (N = 796) and professional drivers (heavy goods vehicles and buses) in Norway and Greece (N = 416). Results from qualitative interviews (N = 61) are also presented. We study safety behaviours hypothesized to vary according to nationality (e.g., aggressive violations), and behaviours hypothesized to vary according to the professional versus private driver dimension (e.g., seat belt use). A central objective is to examine whether the former safety behaviours are more similar among private and professional drivers within countries than among professional and private drivers across national samples, indicating common national road safety cultures among private and professional drivers in the respective countries. The results indicate that aggressive violations are more similar among private and professional drivers within the national samples, than across the national samples, while seat belt use seems to vary according to the professional versus private dimension. The results also indicate a relationship between aggressive violations and accident involvement, although other variables were more strongly correlated. Moreover, drivers’ safety behaviours were influenced by the behaviours that these groups ascribed to other drivers in their countries, indicating the existence of different national road safety cultures. The Greek RSC was characterized by more aggression and violations than the Norwegian RSC, which seemed to be characterized by a higher level of compliance and politeness. The different RSCs may perhaps shed light on the different accident records in the two countries.

Revisiting the hypothesis of sex-biased turtle road mortality

Road mortality poses a major threat to turtle populations. Several studies have suggested that the terrestrial movements associated with nesting increase this risk for females. The Ontario Turtle Conservation Centre (OTCC) is home to the Kawartha Turtle Trauma Centre, which admits 900 or more turtles a year, with road injuries the primary cause of admission. We tested the hypothesis that road mortality in turtles is female-biased using data from injured Midland Painted Turtles (Chrysemys picta marginata), Snapping Turtles (Chelydra serpentina), Blanding’s Turtles (Emydoidea blandingii), and Northern Map Turtles (Graptemys geographica) collected over about 126 000 km2 and admitted to OTCC’s hospital from January 2013 to October 2017. There was no difference in the number of male and female admissions of Midland Painted, Blanding’s, or Snapping Turtles (P &gt; 0.05); however, more female Northern Map Turtles than males were admitted (P &lt; 0.001). Admission of female turtles peaked in June during the nesting season, but male admissions were more evenly distributed throughout the season. Our admissions data provide a temporally unbiased and geographically broad snapshot of turtle–vehicle interactions that can directly inform conservation and management policies. Although our data are not equivalent to mortality rates, these results demonstrate that vehicle strikes can have a substantial impact on both female and male turtles.

Pay or prevent? Human safety, costs to society and legal perspectives on animal-vehicle collisions in São Paulo state, Brazil.

Direct road mortality and the barrier effect of roads are typically identified as one of the greatest threats to wildlife. In addition, collisions with large mammals are also a threat to human safety and represent an economic cost to society. We documented and explored the effects of animal-vehicle crashes on human safety in São Paulo State, Brazil. We estimated the costs of these crashes to society, and we summarized the legal perspectives. On average, the Military Highway Police of São Paulo reported 2,611 animal-vehicle crashes per year (3.3% of total crashes), and 18.5% of these resulted in human injuries or fatalities. The total annual cost to society was estimated at R$ 56,550,642 (US $ 25,144,794). The average cost for an animal-vehicle crash, regardless of whether human injuries and fatalities occurred, was R$ 21,656 (US $ 9,629). The Brazilian legal system overwhelmingly (91.7% of the cases) holds the road administrator liable for animal-vehicle collisions, both with wild and domestic species. On average, road administrators spent R$ 2,463,380 (US $ 1,005,051) per year compensating victims. The logical conclusion is that the Brazilian legal system expects road administrators to keep animals, both wild and domestic species, off the road. We suggest an improved coordination between the laws that relate to animal-vehicle collisions and human safety, and the process for environmental licenses that focusses on reducing collisions with wildlife and providing habitat connectivity. In addition, we suggest better management practices, raising awareness and social change with regard to abandoned domesticated animals including horses, cattle, and dogs. This should ultimately result in a road system with improved human safety, reduced unnatural mortality for both domestic and wild animal species, safe crossing opportunities for wildlife, and reduced monetary costs to society.

Environmental factors influencing road use in a nocturnal insectivorous bird

Many animals avoid roads due to traffic disturbance, but there are also some species that use roads in their everyday life and even obtain resources from them. Understanding the factors that influence the intensity of road use by these species can help understand temporal patterns of road mortality and thereby maximise the cost-effectiveness of mitigation measures. Here, we use road transect counts conducted once a week for 9 consecutive years (2009–2017) to investigate environmental factors influencing road use in the red-necked nightjar (Caprimulgus ruficollis), a nocturnal insectivorous bird that frequents roads to forage and thermoregulate. We found that the intensity of road use by nightjars was affected by ambient temperature, amount of moonlight and wind conditions—all factors known to influence their foraging efficiency and thermoregulatory requirements. Specifically, the highest numbers of nightjars on roads occurred during no-wind conditions and on either dark-cold or bright-warm nights, suggesting that they preferentially use roads for thermoregulation under unfavourable weather conditions or to maximise food intake during periods of increased insect abundance (i.e. warm nights) and improved conditions for visual prey detection (i.e. full moon). Our results illustrate the role of environmental conditions as drivers of rapid changes in the use of roads by animals. Furthermore, this work suggests that analogous studies can be used to inform mitigation measures, so that mitigation efforts to prevent roadkills can be concentrated during periods of expected peaks in animal use of roads.

Landscape correlates of space use in the critically endangered African wild dog Lycaon pictus.

Human-carnivore conflict can threaten human life and livelihoods, leading to retaliation that negatively affects carnivore conservation. The endangered African wild dog Lycaon pictus is prone to human-carnivore conflict. Therefore, it is imperative to understand which landscape features are associated with African wild dog occurrence since selection or avoidance of these features could predict the levels of conflict. We investigated resource selection in the African wild dog in relation to four anthropogenic landscape features (livestock density, agriculture, roads and human land use) within the landscape that may pose a mortality risk, as well as one natural feature (nature reserves). We compared spatio-temporal space use patterns of four African wild dog packs in north-eastern South Africa. Data were collected from one collared individual per pack. These packs constituted approximately 10% of the total remaining African wild dog population in South Africa. Two packs occurred outside of the Kruger National Park and had access to multiple areas with farmland and other anthropogenic features, whereas the remaining two packs mainly occurred within the boundaries of the Kruger National Park but made occasional forays outside of park boundaries. Utilising Resource Selection Functions and GIS analyses, we found that agricultural landscape features, roads and nature reserves were important predictors of African wild dog occurrence for all four packs. In addition to potential conflict with farmers, high odds of occurrence on roads with fast-moving traffic and road mortality was highlighted as a concern for three of the packs. While farms and areas that house livestock were readily available, pack presence occurred in areas with few farms and low livestock densities, pointing to avoidance of areas where human-carnivore conflict and resulting mortality could occur. Our study highlights potential threats to the persistence of the African wild dog, which can be used to inform future conservation efforts of the species.

Road mitigation using tunnels and fences promotes site connectivity and population expansion for a protected amphibian

Habitat loss and fragmentation due to urbanisation and road developments have substantial impacts on amphibian populations and road mitigation measures are increasingly used in order to reduce such risks. However, numerous important questions remain unanswered on the actual effectiveness of such ecological road mitigation projects. We used specially adapted time-lapse recording cameras and a custom image analysis script to monitor the amphibian usage and effectiveness of a multi-tunnel mitigation site in northern England over 4 years and used before-and-after pond survey data to evaluate the mitigation results from a population trend perspective. We monitored four amphibian species, including the European protected great crested newt (Triturus cristatus), the main target of amphibian road mitigation in the UK. Despite substantial evidence of mitigation rejection and U-turn movements inside the tunnels, overall, most amphibians entering tunnels successfully used them to move between the different parts of the site separated by the road. Road fences appeared effective for preventing amphibian road mortality and site connectivity was re-established via the wildlife passage system, with multiple new ponds across the road colonised by amphibians. Unlike frogs and toads, tunnel usage by newts was strongly autumn based, indicating that such systems are mainly suitable for supporting newt dispersal movements between breeding areas. The great crested newt population increased rapidly over the course of the monitoring period, suggesting that, together with habitat replacements and improvements, the road mitigation measures were effective at maintaining site connectivity and as a population conservation measure.