Living on the verge: are roads a more suitable refuge for small mammals than streams in Mediterranean pastureland?

Small mammals in a mountain ecosystem: the effect of topographic, micrometeorological, and biological correlates on their community structure

An increasing number of studies have investigated spatial and temporal patterns in species richness and assemblage composition in mountain ecosystems along altitudinal gradients. Small mammals have been successfully used as indicators of environmental health and as proxies of biodiversity. However, information about the composition and distribution of species assemblages in the mosaic of habitat and rocky landform types at a high altitude is still lacking for most of the mountain regions. Through the use of live traps and camera trapping, we described the small mammal community living above the treeline of the Western Dolomites (Italian Alps), investigating the species richness, abundance of individuals and community composition in relation to topographic, micrometeorological, mesohabitat, and biological correlates. A total of five species and 50 individuals were sampled, analysed, and released. At the extremes of the analysed altitudinal range (i.e. 1900 vs 2900 m a.s.l.), community composition was completely different and species richness was related to elevation, steepness, and vegetation cover. At the same time, the taxonomic distinctness of ground-dwelling arthropods (namely carabid beetles and spiders), a proxy of habitat complexity, showed higher values in areas with a greater small mammal species richness. We found a positive effect of steepness and rocky landform type “carsism” on the number of captured individuals, showing the importance of the availability of shelters and underground burrows for the sampled species. As a confirmation of the altitudinal shift for these species in relation to the ongoing climate change, we detected a negative impact of sub-surface ground temperature on small mammal abundance during the monitoring period. In conclusion, small mammals represent an excellent model for understanding the evolutionary processes of ecosystems, population dynamics under changing environmental conditions, and habitat vulnerabilities.

Effects of roads on small-mammal movements: Opportunities and risks of vegetation management on roadsides

Roads can block animal movement and reduce persistence of species living in road surroundings. Movement restrictions on local populations may even increase extinction risk of abundant small mammals. However, road verges (road managed area between the edge of the road and the beginning of private land) may provide refuge and corridors for small mammals when properly managed. Information on the effects of roads and roadside management on small-mammal movement is still scarce for low traffic roads (<20,000 vehicles per day) crossing well-preserved habitats. We aimed to fill this gap by comparing fine-scale movement patterns of wood mice (Apodemus sylvaticus) in a road and in a similar roadless area without management. Both areas consisted of a well-preserved Mediterranean agro-silvo pastoral system. We studied several movement patterns: road crossings, verge use, length, and direction of movement. Additionally, we assessed how roadside management, animals' sex and residency status, season and microhabitat affect movement at the road area. At the roadless area, we defined a virtual road and verges at equivalent locations to the road area for comparison purposes. We gathered capture-mark-recapture data for two years to characterize movement patterns. Wood mice tended to avoid the road by crossing it less often and moving away from it more frequently than from equivalent locations in the roadless area. Wood mice used road verges more frequently than virtual verges and moved more often parallel to the road than to the virtual road. Road crossings were more frequent after firebreak openings (strips of mowed land) in surrounding areas and near taller shrubs. Also, males used road verges more often than females. Differences on several movement patterns between areas and their trends within the road area can be explained mainly by the presence of the road and roadside vegetation management (e.g., firebreaks openings). We suggest roadside vegetation management practices (e.g., avoid land mowing; maintain vegetation strips) to promote the role of verges as refuges and/or corridors for small mammals.

The effect of habitat reduction by roads on space use and movement patterns of an endangered species, the Cabrera vole Microtus cabrerae

Roads are among the most widespread signs of man’s presence around the globe. From simple low traffic trails to wide and highly used highways, roads have a wide array of effects on wildlife. In the present study, we tested how habitat reduction by roads may affect the space use and movement patterns of the Cabrera vole (Microtus cabrerae), a near-threatened Iberian endemism, often living on road verges. A total of 16 voles were successfully radio-tracked in two habitat patches with different size and proximity to roads. Results showed that individuals from the smaller patch (Verge patch) had smaller and less complex home-ranges than those from the larger patch (Meadow patch). Movement patterns were significantly influenced by the day period but only in individuals from the Verge patch. There was evidence of a barrier effect in both habitat patches, being this effect much more noticeable in the verge population. Overall, this study shows that space use and movement patterns of Cabrera voles near roads may be affected by the degree of habitat reduction imposed by these infrastructures. This suggests that species space use and movement patterns at fine-scale should be accounted for in road planning, even for species that may benefit from road verge habitats as refuges.

Long Arm of Motorway-The Impact of Fenced Road on the Mortality of European Badgers

We studied the impact of the new fenced and accident-safe motorway on the mortality of European badgers Meles meles on local roads in western Poland in 2010-2015. We monitored the badgers mortality on local roads of three categories: main roads, secondary roads and county roads. The study was conducted before and after the opening of the motorway in 2012. We hypothesized that the mortality of badgers is lower due to traffic concentration on motorway. Ninety two badgers were killed in collisions with vehicles on all monitored roads. Mean number of killed badgers was lowest in 2010 before the motorway opening and the highest in 2012. The mortality of badgers on regional roads was highest after the opening of the motorway due to the changes in traffic on the access roads. Within the road network, the mortality of badgers was 5.8 individuals/10 km of road per whole study period with the highest rate on main roads 8.5 individuals/10 km. The badgers mortality was highest on county roads but it was lower than expected in relation to the road network density. The highest vehicle collision risk for badgers of both sexes occurred in June. Distance to human settlements was the only environmental factor that was positively related to badger mortality on roads. We conclude that the new motorway did not reduce the mortality rate of badgers on the adjacent roads because the status of local roads has changed and now they mainly function as access roads to the motorway.

Raptor research during the COVID-19 pandemic provides invaluable opportunities for conservation biology

Research is underway to examine how a wide range of animal species have responded to reduced levels of human activity during the COVID-19 pandemic. In this perspective article, we argue that raptors (i.e., the orders Accipitriformes, Cariamiformes, Cathartiformes, Falconiformes, and Strigiformes) are particularly well-suited for investigating potential 'anthropause' effects: they are sensitive to environmental perturbation, affected by various human activities, and include many locally and globally threatened species. Lockdowns likely alter extrinsic factors that normally limit raptor populations. These environmental changes are in turn expected to influence - mediated by behavioral and physiological responses - the intrinsic (demographic) factors that ultimately determine raptor population levels and distributions. Using this population-limitation framework, we identify a range of research opportunities and conservation challenges that have arisen during the pandemic, related to changes in human disturbance, light and noise pollution, collision risk, road-kill availability, supplementary feeding, and persecution levels. Importantly, raptors attract intense research interest, with many professional and amateur researchers running long-term monitoring programs, often incorporating community-science components, advanced tracking technology and field-methodological approaches that allow flexible timing, enabling continued data collection before, during, and after COVID-19 lockdowns. To facilitate and coordinate global collaboration, we are hereby launching the 'Global Anthropause Raptor Research Network' (GARRN). We invite the international raptor research community to join this inclusive and diverse group, to tackle ambitious analyses across geographic regions, ecosystems, species, and gradients of lockdown perturbation. Under the most tragic of circumstances, the COVID-19 anthropause has afforded an invaluable opportunity to significantly boost global raptor conservation.

Use of underpasses by animals on a fenced expressway in a suburban area in western Poland

Expressways act as barriers to animals that block free movement in their habitats, especially when the roads are continuously fenced to prevent collisions between animals and vehicles. Various types of animal passages have been repeatedly studied in terms of their utility, albeit rather less frequently in the suburban environment. We conducted our research in a section of the fenced expressway S3 connecting two closely located cities in western Poland (Lubuskie province). Over the course of one year, we monitored four underpasses intended for small- and medium-sized animals using tracks. The underpasses were inspected weekly. Animal traces most frequently found belonged to roe deer Capreolus capreolus (20.9%), red fox Vulpes vulpes (15.1%), wild boar Sus scrofa (14%), and domestic dog Canis l. familiaris (12.4%). Surprisingly, the results of our study indicate that underpasses for small and medium mammals are also used by ungulate mammals. The use of the underpasses varied seasonally, being the highest in spring (37.9%) and the lowest in winter (10.4%). Moreover, seasonal differences in the use of passages were related to particular species/groups of animal species. We found that 22% of animals that entered the passage did not completely traverse it. People accounted for 17.1% of all stated traces in the underpasses. Stagnant water in the underpasses reduced the number of predatory mammals and wild boars using the underpasses but did not affect the activity of roe deer. These studies indicate that animal underpasses located in suburban areas are used by many species of animals despite the activity of humans and domesticated mammals.

Road verges provide connectivity for small mammals: A case study with wood mice (Apodemus sylvaticus) in an agro-silvo pastoral system

Roads disrupt landscape connectivity for many terrestrial mammals. These infrastructures can be barriers to movement thereby threatening population persistence. Nonetheless, small mammals may use road verges as habitat or corridor, thus increasing migration across intensively managed landscapes. However, in well-preserved habitats where road verges show a similar vegetation structure to surrounding areas, their role is still unknown. Road verges would have an important role as fine-scale connectivity providers for small mammals in a well-preserved habitat depending on land management on road surroundings. We aimed to quantify the effects of road verges and paved lanes on the fine-scale landscape connectivity for the wood mouse (Apodemus sylvaticus) in a well-preserved Mediterranean woodland. Additionally, we assessed the impact on connectivity of vegetation cutting on verges and of management in surrounding areas (i.e. firebreaks, grazing, ploughing and cork stripping). We quantified connectivity using graph theory based on two years of capture-recapture data. We compared a set of connectivity metrics (derived from the probability of connectivity index) in a road area and in a virtual roadless scenario. We found that the presence of the road reduced overall fine-scale landscape connectivity, acting as a partial barrier for wood mice movement. However, verges had a key role in promoting movement on road surroundings. Vegetation cutting on verges, and land ploughing in the surrounding landscape were the only management activities compromising connectivity. Our study supports the already known role of road verges as habitat corridors for small mammals. However, it goes beyond existing knowledge by quantifying the connectivity enhancement provided by road verges and demonstrating that this role is highly relevant even in well-preserved landscapes. Therefore, our findings emphasize the critical role of road verges and suggest important management options to enhance landscape connectivity for small mammals.

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 effects on bat activity depend on surrounding habitat type

The effects of roads on bats are still a poorly documented issue. Most of the available research focuses on large and high-traffic highways, while low-medium-traffic roads are often assumed to have negligible impacts. However, small roads are ubiquitous in landscapes around the world. We examined the effects of these roads, as well as habitat types, on the activity of three bat guilds (short-, mid- and long-range echolocators) and the most common bat species Pipistrellus kuhlii. We performed three bat acoustic surveys between May and October 2015, with these surveys being performed along twenty transects that were each 1000 m long and perpendicular to three roads with different traffic volumes. The surveys were performed in dense Mediterranean woodland ("montado") and open agricultural field habitats, which were the two dominant land uses. At each transect, bat activity was simultaneously registered at 0, 50, 100, 200, 500 and 1000 m from the road with the use of an ultrasound recorder. According to the generalized linear mixed effects models, the overall activity of bats and of the short- and mid-range echolocators increased with increased distance from the roads and was dependent on the surrounding habitats. In contrast, the long-range echolocators and P. kuhlii were more tolerant to road. Our results also show that the activity was higher in woodland areas, however road verges seem to be a significant habitat in an open agricultural landscape. The major negative effects extended to approximately 300 m from the roads in woodlands and penetrate further into the open field (>500 m). The management of roadside vegetation, combined with the bat habitat improvement in areas that are further from the roads, may mitigate the negative effects. To make road-dominated landscapes safer for bats, the transport agencies need to balance the trade-offs between habitat management and road kill risk.

Infrastructure features outperform environmental variables explaining rabbit abundance around motorways

Human disturbance is widespread across landscapes in the form of roads that alter wildlife populations. Knowing which road features are responsible for the species response and their relevance in comparison with environmental variables will provide useful information for effective conservation measures. We sampled relative abundance of European rabbits, a very widespread species, in motorway verges at regional scale, in an area with large variability in environmental and infrastructure conditions. Environmental variables included vegetation structure, plant productivity, distance to water sources, and altitude. Infrastructure characteristics were the type of vegetation in verges, verge width, traffic volume, and the presence of embankments. We performed a variance partitioning analysis to determine the relative importance of two sets of variables on rabbit abundance. Additionally, we identified the most important variables and their effects model averaging after model selection by AICc on hypothesis‐based models. As a group, infrastructure features explained four times more variability in rabbit abundance than environmental variables, being the effects of the former critical in motorway stretches located in altered landscapes with no available habitat for rabbits, such as agricultural fields. Model selection and Akaike weights showed that verge width and traffic volume are the most important variables explaining rabbit abundance index, with positive and negative effects, respectively. In the light of these results, the response of species to the infrastructure can be modulated through the modification of motorway features, being some of them manageable in the design phase. The identification of such features leads to suggestions for improvement through low‐cost corrective measures and conservation plans. As a general indication, keeping motorway verges less than 10 m wide will prevent high densities of rabbits and avoid the unwanted effects that rabbit populations can generate in some areas.

Heterogeneous road networks have no apparent effect on the genetic structure of small mammal populations

Roads are widely recognized to represent a barrier to individual movements and, conversely, verges can act as potential corridors for the dispersal of many small mammals. Both barrier and corridor effects should generate a clear spatial pattern in genetic structure. Nevertheless, the effect of roads on the genetic structure of small mammal populations still remains unclear. In this study, we examine the barrier effect that different road types (4-lane highway, 2-lane roads and single-lane unpaved roads) may have on the population genetic structure of three species differing in relevant life history traits: southern water vole Arvicola sapidus, the Mediterranean pine vole Microtus duodecimcostatus and the Algerian mouse Mus spretus. We also examine the corridor effect of highway verges on the Mediterranean pine vole and the Algerian mouse. We analysed the population structure through pairwise estimates of FST among subpopulations bisected by roads, identified genetic clusters through Bayesian assignment approaches, and used simple and partial Mantel tests to evaluate the relative barrier or corridor effect of roads. No strong evidences were found for an effect of roads on population structure of these three species. The barrier effect of roads seems to be site-specific and no corridor effect of verges was found for the pine vole and Algerian mouse populations. The lack of consistent results among species and for each road type lead us to believe that the ability of individual dispersers to use those crossing structures or the habitat quality in the highway verges may have a relatively higher influence on gene flow among populations than the presence of crossing structures per se. Further research should include microhabitat analysis and the estimates of species abundance to understand the mechanisms that underlie the genetic structure observed at some sites.