Small Mammal Populations Research Articles

Influence of vegetation type and prescribed fire on Peromyscus abundance in a longleaf pine ecosystem

ABSTRACTPrescribed fire temporarily can alter food and cover resources for ground‐dwelling wildlife, potentially leading to changes in animal abundance. Small mammals are an important ecosystem component in many terrestrial communities and depend on ground‐level vegetation most commonly affected by prescribed fire. In this complex system of food and cover availability where easier access to food might compromise cover, and vice versa, it is imperative to study postfire habitat use by mice and other ground‐dwelling wildlife. We evaluated effects of time since burn and vegetation type on Peromyscus spp. abundance in a longleaf pine (Pinus palustris) ecosystem in Fort Bragg Military Installation, North Carolina, USA, during 2011 and 2012. We trapped in 5 vegetation types and captured 208 individual Peromyscus. Peromyscus abundance did not differ among 1, 2, and 3 years postburn upland pine vegetation types, although we noted a trend of decreasing abundance as time since burn increased; however, abundance was greater in the lowland hardwood vegetation type than in open areas (i.e., military drop zones). The lack of an effect of time since burn could be due to the short fire‐return interval at the study site, which limited the time for postburn shifts in the composition of the understory from herbaceous to woody plant species. Therefore, we suggest future research in the longleaf pine ecosystem incorporate a wider time frame to assess short‐ and long‐term effects of fire on small mammal populations. © 2017 The Wildlife Society.

Small mammal abundance in Mediterranean Eucalyptus plantations: how shrub cover can really make a difference

In the last decades production forests have expanded their range worldwide, and in many regions (e.g., southern Europe) Eucalyptus spp. have been the target species used by foresters. However, Eucalyptus characteristics and management intensity of its plantations may impose constraints to local wildlife, often considered highly harmful for wildlife. However, although Portugal and Spain encompass the widest Eucalyptus production forests in Europe, and the Mediterranean area is a biodiversity hotspot, no study has yet tested specifically the impact of this exotic forest inner structure on rodent’s populations. Aiming to evaluate whether this negative influence of Eucalyptus stands’ on wildlife was associated with any specific structural characteristics of plantations, we tested the effect of plantation’s understory structure and homogeneity on small mammal abundance and population structure. Small mammal were live-trapped in autumn and spring in nine sampling sites in Eucalyptus plantations in central west Portugal, one km apart. By using a GLMM approach we detected that the percentage of shrub coverage was the main driver of small mammal abundance, although season (autumn) also showed a positive influence. Only for Crocidura russula we detected an influence of stands homogeneity in population structure, with a sex-ratio variation according to edge distance. Thus, our study clearly indicates that by maintaining an understory layer within exotic Eucalypus plantations, managers may assure that these anthropic environments may still support an abundant small mammal community, thus contributing to the preservation of key ecosystems functions.

Strong "bottom-up" influences on small mammal populations: State-space model analyses from long-term studies.

“Bottom‐up” influences, that is, masting, plus population density and climate, commonly influence woodland rodent demography. However, “top‐down” influences (predation) also intervene. Here, we assess the impacts of masting, climate, and density on rodent populations placed in the context of what is known about “top‐down” influences. To explain between‐year variations in bank vole Myodes glareolus and wood mouse Apodemus sylvaticus population demography, we applied a state‐space model to 33 years of catch‐mark‐release live‐trapping, winter temperature, and precise mast‐collection data. Experimental mast additions aided interpretation. Rodent numbers in European ash Fraxinus excelsior woodland were estimated (May/June, November/December). December–March mean minimum daily temperature represented winter severity. Total marked adult mice/voles (and juveniles in May/June) provided density indices validated against a model‐generated population estimate; this allowed estimation of the structure of a time‐series model and the demographic impacts of the climatic/biological variables. During two winters of insignificant fruit‐fall, 6.79 g/m2 sterilized ash seed (as fruit) was distributed over an equivalent woodland similarly live‐trapped. September–March fruit‐fall strongly increased bank vole spring reproductive rate and winter and summer population growth rates; colder winters weakly reduced winter population growth. September–March fruit‐fall and warmer winters marginally increased wood mouse spring reproductive rate and September–December fruit‐fall weakly elevated summer population growth. Density dependence significantly reduced both species' population growth. Fruit‐fall impacts on demography still appeared after a year. Experimental ash fruit addition confirmed its positive influence on bank vole winter population growth with probable moderation by colder temperatures. The models show the strong impact of masting as a “bottom‐up” influence on rodent demography, emphasizing independent masting and weather influences; delayed effects of masting; and the importance of density dependence and its interaction with masting. We conclude that these rodents show strong “bottom‐up” and density‐dependent influences on demography moderated by winter temperature. “Top‐down” influences appear weak and need further investigation.

Influence of Removal Sampling of Small Mammals on Abundance and Diversity Attributes: Scientific Implications

Terrestrial small mammals occupy a variety of temperate and boreal forests in North America and Eurasia and contribute to biodiversity within these ecosystems. Researchers commonly use a variation of removal trapping to sample small-mammal populations and communities in these systems. However, it is not known if recurrent removal sampling might bias abundance estimates or alter the very populations under study. We addressed 2 questions: (1) are estimates of population size and species richness and diversity gained from removal trapping different from those based on live-trapping? and (2) what residual impact does removal trapping have on small-mammal populations and communities, as revealed by live-trapping? In 2 experiments (summer 2004 and autumn 2005), we compared undisturbed controls (non-removal) with removal sampling for 5-, 10-, and 30-night periods. Total abundance estimates during removal periods were dramatically higher (up to 3-fold) on non-removal than removal sites in both experiments. Mean abundance of the 2 most common species, deer mouse (Peromyscus maniculatus) and northwestern chipmunk (Neotamias amoenus), were substantially higher on non-removal than removal sites in the autumn experiment. The longer the removal interval, the deeper the degree of departure from non-removal levels of abundance. Species richness during removal periods also followed the pattern of abundance, whereby new, uncommon species appeared on removal sites, but not non-removals, during the autumn experiment. The residual impact of removal trapping, as revealed by live-trapping, indicated that abundance estimates were up to 4.5-fold higher on non-removal than postremoval sites and continued for at least 1 month as the small mammal community reorganized itelf via immigration and settlement. Species diversity was still significantly different among removals 8 months after the autumn removal period. Removal-trapping over variable lengths (5 to 30 nights) may not provide an accurate picture of the abundance or diversity of small mammals.

Trait-demography relationships underlying small mammal population fluctuations.

Large-scale fluctuations in abundance are a common feature of small mammal populations and have been the subject of extensive research. These demographic fluctuations are often associated with concurrent changes in the average body mass of individuals, sometimes referred to as the 'Chitty effect'. Despite the long-standing recognition of this phenomenon, an empirical investigation of the underlying coupled dynamics of body mass and population growth has been lacking. Using long-term life-history data combined with a trait-based demographic approach, we examined the relationship between body mass and demography in a small mammal population that exhibits non-cyclic, large-scale fluctuations in abundance. We used data from the male segment of a 25-year study of the monogamous prairie vole, Microtus ochrogaster, in Illinois, USA. Specifically, we investigated how trait-demography relationships and trait distributions changed between different phases of population fluctuations, and the consequences of these changes for both trait and population dynamics. We observed phase-specific changes in male adult body mass distribution in this population of prairie voles. Our analyses revealed that these changes were driven by variation in ontogenetic growth, rather than selection acting on the trait. The resulting changes in body mass influenced most life-history processes, and these effects varied among phases of population fluctuation. However, these changes did not propagate to affect the population growth rate due to the small effect of body mass on vital rates, compared to the overall differences in vital rates between phases. The increase phase of the fluctuations was initiated by enhanced survival, particularly of juveniles and fecundity, whereas the decline phase was driven by an overall reduction in fecundity, survival and maturation rates. Our study provides empirical support, as well as a potential mechanism, underlying the observed trait changes accompanying population fluctuations. Body size dynamics and population fluctuations resulted from different life-history processes. Therefore, we conclude that body size dynamics in our population do not drive the observed population dynamics. This more in-depth understanding of different components of small mammal population fluctuations will help us to better identify the mechanistic drivers of this interesting phenomenon.

Road effects on demographic traits of small mammal populations

Recent studies have highlighted the positive effects of road verges on the abundance of small mammals. However, most of these studies occurred in intensively grazed or cultivated areas, where verges were the last remnants of suitable habitats, which could mask the true effects of roads on population traits. We analysed the effects of roads on small mammal populations living in a well-preserved Mediterranean forest. We used the wood mouse (Apodemus sylvaticus) as a model of forest-dwelling small mammals that probably are among the species most affected by road clearings. Our study compared populations in similar habitat areas with and without road influence. We assessed abundance, survival and temporary emigration using extended Pollock’s robust design capture-recapture models. Moreover, we analysed population turnover, sex ratio, age structure and body condition. We found that wood mouse abundance and body condition were lower at the road bisected area, whereas the remaining population traits were similar. This suggests that the reduced habitat availability and quality due to the physical presence of the road and verge vegetation clearing are the main drivers of demographic differences in wood mouse populations between areas. Nevertheless, our results also suggest that in high-quality habitats surrounding national roads, wood mouse populations present similar dynamics to others living in undisturbed areas, despite the decrease in abundance and body condition. Overall, the often-reported increased small mammal abundance in road surroundings should not be generalized independently of habitat quality or to other population traits.

How small cities affect the biodiversity of ground-dwelling mammals and the relevance of this knowledge in planning urban land expansion in terms of urban wildlife

Fundamental principles regarding urban biodiversity are based on studies conducted in large cities. However we cannot know whether the same phenomena occur in smaller cities or how small cities affect biodiversity. Small cities are an inherent element of urbanization and in the future, most global urban growth is expected to take place in small and medium-sized cities. Understanding the effects of small cities on biodiversity will be an important aspect in planning urban land expansion. Our study examined the effects of a small city on communities of small ground-dwelling mammals on 41 sites arranged in a four step gradient of urbanization. In 6700 trap-days, we caught 2333 individuals comprising 15 species. In the downtown area the same phenomena as those described for large cities were observed: a reduction in species richness and diversity, a decline in the abundance of urban sensitive species and an increase in synurbic species. However, in contrast to large city studies, green areas outside the downtown area did not differ from rural sites in small mammal population parameters. This phenomenon of relatively unchanged fauna outside the downtown area shows that small cities have the potential to maintain a high level of diversity of small ground-dwelling mammals if appropriate planning of further building expansion is implemented. More studies of small cities are needed to better assess their impact on biodiversity. This knowledge can then be applied in better planning for urban wildlife. Generalizations based solely on large city studies are inadequate and may lead to incomplete or inappropriate conservation strategies for small cities.

Население мелких млекопитающих в условиях техногенного загрязнения Северного Казахстана (на примере г. Павлодар)

Население мелких млекопитающих в условиях техногенного загрязнения Северного Казахстана (на примере г. Павлодар)

Spatial-Typological Structure and Organization of the Population of Small Mammals of the Prealtai Plain

Spatial-Typological Structure and Organization of the Population of Small Mammals of the Prealtai Plain

An evaluation of small-mammal use of constructed wildlife crossings in ski resorts

Context Infrastructure development in ski-resort areas has led to the modification of slopes and, often, the replacement of native plant species with exotic grasses. Modified ski slopes are effectively linear areas of disturbance that separate natural habitat and provide barriers to the movement of native animal species. To overcome these barriers, boulder-filled and culvert-style wildlife crossings have been constructed across disturbed ski slopes and under roadways to facilitate the movement of small native mammal species among areas of remnant habitat, but generally they differ in size and locality. The use of boulder-filled and under-road culvert crossings of different length has not been evaluated. Aims We determine whether fauna utilise wildlife crossings in ski resorts and whether variations in crossing length influence the species using the crossings. Methods We monitored boulder-filled crossings of two size classes (long or short) biannually from March 2009 to April 2013, using hair tubes. We monitored an additional two under-road culvert crossings with remote infrared cameras. Key results The results indicated that all crossings, regardless of size, are utilised by small mammals. However, we detected threatened species, such as Mastacomys fuscus (broad-toothed rat), more frequently in crossings of greater length. Conclusions To maintain linkages for small-mammal populations within ski resorts, we recommend the continued use of boulder-filled crossings on ski slopes. These crossings may be particularly important in facilitating the movement of small mammals across wide areas of ski-slope disturbance. Implications The context and maintenance of crossings is likely to be important for their long-term use by small mammals, as are complementary strategies to restore structural habitat connectivity on ski slopes, such as strategically implemented native vegetation plantings.

Habitat structure and disturbance affect small mammal populations in Mediterranean forests

Habitat structure, the physical arrangement of objects in space, affects animal populations, ecological interactions, species diversity, and ecosystem functioning. Conventional forest management practices that reduce habitat structural complexity are thus under reappraisal, and there are increasing efforts to understand how habitat structure affects functionally important species. We investigate here the effect of habitat structures on small mammal dens and their interactions with widespread antagonistic species (wild boars). Among habitat structures we considered tree dimension (diameter), shrub cover, rock cover, dead wood volume, and stump area. Ground cover with rooting signs measured wild boar disturbance. The number of small mammal dens was related positively to rock cover and tree diameter, and negatively to wild boar disturbance. Additionally, a positive interaction between wild boar disturbance and tree diameter emerged, showing that the effect of big trees on small mammal nesting was more evident with higher levels of disturbance. This study suggests that habitat structures that can be affected by forest management provide effective refuges for functionally important species. The effect of habitat structure on species survival and interactions thus needs to be addressed to understand ecosystem management and functioning.

Long-term data from a small mammal community reveal loss of diversity and potential effects of local climate change.

Climate change affects distribution and persistence of species. However, forecasting species’ responses to these changes requires long-term data series that are often lacking in ecological studies. We used 15 years of small mammal trapping data collected between 1978 and 2015 in 3 areas at Doñana National Park (southwest Spain) to (i) describe changes in species composition and (ii) test the association between local climate conditions and size of small mammal populations. Overall, 5 species were captured: wood mouse Apodemus sylvaticus, algerian mouse Mus spretus, greater white-toothed shrew Crocidura russula, garden dormouse Eliomys quercinus, and black rat Rattus rattus. The temporal pattern in the proportion of captures of each species suggests that the small mammal diversity declined with time. Although the larger species (e.g., E. quercinus), better adapted to colder climate, have disappeared from our trapping records, M. spretus, a small species inhabiting southwest Europe and the Mediterranean coast of Africa, currently is almost the only trapped species. We used 2-level hierarchical models to separate changes in abundance from changes in probability of capture using records of A. sylvaticus in all 3 areas and of M. spretus in 1. We found that heavy rainfall and low temperatures were positively related to abundance of A. sylvaticus, and that the number of extremely hot days was negatively related to abundance of M. spretus. Despite other mechanisms are likely to be involved, our findings support the importance of climate for the distribution and persistence of these species and raise conservation concerns about potential cascading effects in the Doñana ecosystem.

Overview of occurrence of the Short-eared Owl Asio flammeus between 1995 and 2015 in Slovenia and its probable breeding in irruptive year 2008

Abstract Between 1995 and 2015 the number of records of Short-eared Owl Asio flammeus in Slovenia increased drastically, especially after 2007, but the species occurred regularly every year since 2002. Before that, the Short-eared Owl was regarded as a very rare migrant in Slovenia. Most of the observations were from wintering and migration periods, and the most important areas for the species in Slovenia were Ljubljansko barje, Lake Cerknica, surroundings of the water reservoir Medvedce and coastal wetlands. In 2008 and 2013 the Short-eared Owl occurred in large numbers, and these years were regarded as irruptive. Flocks of 2 to 8 birds were observed. At Ljubljansko barje, increased numbers of observed Short-eared Owls coincided with a large population of small mammals (species of the genus Apodemus and Microtus) and poor snow cover in 2008, and at least three communal roost sites were found that year. In the irruptive year 2013 there was a greater number of Short-eared Owls observed at the Medvedce water reservoir. On the plain at Lesce near the village of Smokuč an injured second year female was found at the end of March 2008 with a developing brood patch in its initial stage. It is likely that the female attempted to nest, which confirms the status of the species as occasional breeder in Slovenia. The last confirmed breeding in Slovenia was recorded in 1936 at Ljubljansko barje. In addition to local conditions (population of small mammals, snow cover) the frequency of occurrence of the Short-eared Owl in Slovenia is also affected by the population of development in the Boreal region and changes in migratory characteristics of the species in Europe. Therefore, an increase of the number of Short-eared Owls in Slovenia is expected in the future, as well as breeding attempts by this nomadic owl in seasons with high populations of small mammals and green winters, of course, if appropriate meadow habitat is still preserved.

Effects of forest management on density and survival in three forest rodent species

Several studies have shown that small mammal communities are influenced by silvicultural activities, possibly because these affect the quality of wildlife habitats. Previous research mainly focused on community parameters and abundance of target species, however the most robust way to study the impacts of forestry on wildlife is to follow a demographic-response approach. Investigating multiple demographic measurements is essential to understand how populations respond to forest management, nevertheless studies focusing on multiple demographic parameters are lacking. Our analyses targeted individual survival and population density, to understand the demographic mechanisms by which forest management exerts its effects on small mammals. We focused on the populations of Apodemus flavicollis, A. sylvaticus and Myodes glareolus, constituting the guild of forest- and ground-dwelling rodents in central Italy. Populations were monitored for three years in a continuous forest subject to different management practices (mainly coppicing activities and conifer afforestation). We identified four forest management types (three coppice stands logged in different years and a conifer plantation) where we selected 12 sampling areas. We sampled a total of 31,752 trap-nights capturing more than 1350 individuals. We also gathered quantitative data on the amount of trophic and cover resources in each area to better interpret the response of populations to silvicultural activities. For all the three species, coppicing activities had strong positive effects on population density, which were, in some cases, matched by similar effects on individual survival whereas afforestation of conifer plantations negatively affected populations of A. flavicollis and M. glareolus. We found that different types of forest management, such as the recently coppiced stands, did not create high-density sinks but, rather, enhanced the carrying capacity of the habitats by increasing the availability of cover and food resources. On the contrary, the high forest resulted to be less preferred habitat for A. sylvaticus and M. glareolus, possibility due to its lack of food and cover resources. Our analyses encompassing multiple population parameters allowed us to highlight the mechanisms by which forest management affects small mammal populations.

The importance of considering both taxonomic and habitat guild approaches in small mammal research

AbstractStudies on the effects of habitat fragmentation on small mammals often lead to confounding results as they only consider taxonomic groups in their analysis and neglect functional diversity of the communities. Here we describe the structure and composition of small mammal communities at 22 sites, ranging from 41 to 7035 ha, in a hyper‐fragmented landscape of an Amazonia‐Cerrado ecotone. Also, in considering a taxonomic and habitat guild approach, we report the effects of habitat structures and patch spatial attributes on richness, abundance and species composition. Small mammal richness reported in southern Amazonia (N = 23 species) is greater than most previous studies in the tropics. All rare small mammals captured in this study were forest interior species. Richness of forest interior species was positively related to larger patches, as shown by the species–area relationship. However, 52% of the small mammal species were in forest fragments smaller than 50 ha, highlighting the importance of preserving both large and small forest fragments in a landscape with accelerated habitat reduction. Richness of edge‐tolerant species was not associated with the tested variables, yet edge‐tolerant species were more abundant in degraded environments. Marsupials were positively associated with vertical habitat structures, while rodents were more strongly related to a ground‐level habitat structure. The landscape studied is extremely variable and has contributed to the difficulty in detecting clear patterns, particularly when considering only one approach. Because of the complementary outputs when analysing either taxonomic groups or habitat guilds, we recommend the use of multi‐taxa studies of different guilds to assist decision makers in designing conservation strategies and appropriate management of small mammal populations.

The short-term impact of abundant fruit upon deer mouse (Peromyscus maniculatus), southern red-backed vole (Myodes gapperi), and woodland jumping mouse (Napaeozapus insignis) populations

Fruit has been identified as an important and potentially population-restricting food for southern red-backed voles (Myodes gapperi (Vigors, 1830)), deer mice (Peromyscus maniculatus (Wagner, 1845)), and woodland jumping mice (Napaeozapus insignis (Miller, 1891)). We added domestic dried strawberries (Fragaria × ananassa (Weston) Duchesne ex Rozier (pro sp.)) and European black currants (Ribes nigrum L.), which have native analogues and are preferred foods of these rodents, to white spruce (Picea glauca (Moench) Voss) plantations from May through August 2011 and 2012 to test fruit and fruit-based carbohydrate’s short-term (1–2 years) impact on these rodent populations. We used mark–recapture to estimate density, percentages of population that were juvenile and breeding female, mean home-range size, and body mass during spring and summer of both years, and fecundity via placental scars from euthanized females in summer 2012. Fruit enhancement had no apparent effect on our species’ fecundity, proportion of breeding females or juveniles during spring and summer of either year, nor were there differences among these metrics in spring 2012 following 2011 fruit additions. Overall, there were no impacts to the short-term adult population dynamics for any species during fruit addition. We are led to believe that short-term pulses of fruit and (or) fruit-based carbohydrate abundance do little to influence temperate forest small-mammal populations.

Large Herbivore Grazing Limits Small-Mammal Densities in Finnish Lapland

Grazing by large mammals can affect small-mammal populations by modifying the ground-layer vegetation, which provides them with food and shelter. The aim of this study was to investigate the impact of semi-domesticated reindeer grazing on smallmammal abundance in boreal forests/subarctic tundra ecosystems in a large-scale exclosure experiment in northernmost Finnish Lapland. In our experiment spanning four years, reindeer grazing affected the abundance of arvicoline voles, which were less abundant in grazed areas. This was probably due to a reduction in the abundance and height of bilberry, an important forage plant for both voles and reindeer. Changes in ground-layer vegetation affected the general condition of bank voles, which had significantly lower body mass in grazed areas. The abundance of insectivorous shrews was also reduced by grazing, probably due to a reduction in ground-dwelling invertebrates as an indirect effect of changes in the composition of ground-layer vegetation. A grazing-induced red...

Rabbits as Food at the end of the Upper Palaeolithic at Molí del Salt (Catalonia, Spain)

AbstractMany factors have been causally linked to the diversification of hunting during the European Palaeolithic: declining supplies of high‐ranked prey, considerable human demographic growth, reduced residential mobility, larger populations of ubiquitous small mammals and significant technological developments. However, small prey exploitation was not uniform: the European rabbit (Oryctolagus cuniculus) is the most frequent species in the Upper Palaeolithic archaeological record of the Iberian Peninsula – south and Mediterranean area – and Southern France. This is demonstrated at Molí del Salt, an Upper Palaeolithic site located at Vimbodí (Catalonia, Spain), whose mammal fauna stands out for the predominance of rabbits [91% of minimum number of individuals (n = 136)]. We analysed the faunal remains from one level [Asup (c. 12 700–13 000 cal BP)] in order to identify the agent responsible for the faunal accumulation, and to reconstruct aspects of procurement and consumption that shed light on Palaeolithic subsistence strategies in the Northeast Iberian Peninsula. Our results indicate that human agency rather than carnivore activity was responsible for the bone accumulation at Molí del Salt. We identified all the stages in the consumption sequence from skinning to ingestion. We argue that the rabbits were mostly harvested during summer or winter or both seasons. Clearly, the European rabbit was a target species for the human groups which lived at Molí del Salt providing meat, and skin. Copyright © 2016 John Wiley & Sons, Ltd.

Interactive effects of exogenous and endogenous factors on demographic rates of an African rodent

Exogenous and endogenous environmental factors can have simultaneous additive as well as interacting effects on life‐history traits. Ignoring such interactions can lead to a biased understanding of variability in demographic rates and consequently population dynamics. These interactions have been the focus of decades‐long debates on the mechanisms underlying small mammal population fluctuations. They have often been studied indirectly through seasonal effects, but studies considering them directly and more mechanistically are rare. We investigated the joint effects of exogenous (temperature, food availability) and endogenous (population density) factors on the demographic rates of a group‐living diurnal rodent, the African striped mouse Rhabdomys pumilio using nine‐year mark–recapture data from a population in the Succulent Karoo, South Africa. In general, higher temperatures and lower food availability were associated with higher survival, whereas high population densities were either beneficial or detrimental to survival depending on interacting food availability. High reproductive rates were related to lower temperatures, higher food availability and lower population density, and interactions among environmental factors mediated the strength of these relationships. Our study highlights the complex ways in which different environmental factors can interact to shape demographic rates and emphasizes the importance of explicitly including interactions among exogenous and endogenous factors into studies of population dynamics.

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.