Do roads alter the trophic behavior of the mesocarnivore community living close to them?

Roads have impacts on the fauna arising from habitat fragmentation, roadkill and the barrier effect. Furthermore, roads lead species to change their activity with repercussions on predator– prey interactions and trigger indirect effects that are currently unknown. This study analyzes the effect of a motorway on the trophic behavior of the terrestrial carnivore community of its surroundings. Monthly scat sampling was conducted over a year at three distances from a motorway (0–50 m, 500–550 m and 1000–1050 m). We collected 498 scats, these originating from red fox (39.16%), cat (24.50%), stone marten (24.09%) and badger (12.25%). The relative abundance of the trophic resources in them was estimated together with the trophic diversity and niche overlap of the carnivore species. The results showed a distinct effect of distance from the road on trophic behavior of carnivores, as well as differences between species and seasons. The scats nearest the road had 10–20% more biomass of small mammals, equivalent in relative terms to a 21–48% increase in small mammals’ biomass when compared with scats collected further from the road. This finding indicates changes in predator–prey interactions near the road and shows that the human-generated structural and functional changes to ecosystems spread throughout trophic networks.info:eu-repo/semantics/publishedVersio

Are motorways potential stressors of roadside wood mice (Apodemus sylvaticus) populations?

Linear infrastructures represent one of the most important human impacts on natural habitats and exert several effects on mammal populations. Motorways are recognized as a major cause of habitat fragmentation and degradation and of biodiversity loss. However, it is unknown whether motorways lead to increased physiological stress reactions in wild animal populations. We analysed faecal corticosterone metabolites (FCM) in wild populations of wood mice (Apodemus sylvaticus) living in a well-preserved Mediterranean agro-pastoral woodland at different distances (verge, 500 m and 1000 m) from the AP-51 motorway in Spain. Wood mice were captured with Sherman live traps, and fresh faecal samples from 424 individuals were collected and analyzed in the laboratory. The quantification of FCM was performed by a 5a-pregnane-3b,11b, 21-triol-20-one enzyme immunoassay. Results showed that females had higher FCM levels than males, and these levels were higher in breeding females. In addition, FCM levels were positively correlated with body weight of individuals. Wood mice captured where cattle were present showed higher FCM levels than individuals living where cattle were not detected. FCM levels were higher in non-breeding individuals living close to the motorway compared with FCM levels in those individuals captured further from the motorway. This is the first study showing evidence of the motorways' impact on physiological stress reactions in wild wood mice populations. Understanding how free-living animals are influenced by human interventions could help to understand other subtle changes observed in wild animal populations. Since mice are used world-wide as research models these results could open new perspectives testing human influence on the natural environment and trade-offs of species in degraded ecosystemsThis research has been funded by the projects: CENIT-OASIS supported by CDTI of the Spanish Ministry of Science and Innovation, REMEDINAL-2 S-2009/AMB/1783 and CCG10-UAM/AMB-5325 (Comunidad de Madrid together with the European Social Fund and Universidad Autónoma de Madrid). A. Navarro-Castilla was supported by a FPU grant from the Ministerio de Educación y Ciencia of Spai

Disentangle the Causes of the Road Barrier Effect in Small Mammals through Genetic Patterns.

Road barrier effect is among the foremost negative impacts of roads on wildlife. Knowledge of the factors responsible for the road barrier effect is crucial to understand and predict species' responses to roads, and to improve mitigation measures in the context of management and conservation. We built a set of hypothesis aiming to infer the most probable cause of road barrier effect (traffic effect or road surface avoidance), while controlling for the potentially confounding effects road width, traffic volume and road age. The wood mouse Apodemus sylvaticus was used as a model species of small and forest-dwelling mammals, which are more likely to be affected by gaps in cover such as those resulting from road construction. We confront genetic patterns from opposite and same roadsides from samples of three highways and used computer simulations to infer migration rates between opposite roadsides. Genetic patterns from 302 samples (ca. 100 per highway) suggest that the highway barrier effect for wood mouse is due to road surface avoidance. However, from the simulations we estimated a migration rate of about 5% between opposite roadsides, indicating that some limited gene flow across highways does occur. To reduce highway impact on population genetic diversity and structure, possible mitigation measures could include retrofitting of culverts and underpasses to increase their attractiveness and facilitate their use by wood mice and other species, and setting aside roadside strips without vegetation removal to facilitate establishment and dispersal of small mammals

Comparison of FCM concentrations (ng/g dry faeces; mean ± SE) according to breeding condition for males and females.

<p>Asterisks indicate significant differences (**p<0.01).</p

Log-transformed concentrations (mean ± SE) of faecal corticosterone metabolites (FCM, ng/g dry faeces) in breeding and non-breeding individuals in relation to the distance to the motorway.

<p>Significant differences are indicated by asterisks (*p<0.05).</p

Results of the General Linear Model testing the effects of individual and environmental variables on faecal corticosterone metabolites in wood mouse.

<p>Results of the General Linear Model testing the effects of individual and environmental variables on faecal corticosterone metabolites in wood mouse.</p

Simulation parameters, default values and range used in sensitivity analysis.

<p>Simulation parameters, default values and range used in sensitivity analysis.</p

Values of <i>F</i>_ST, <i>G”</i>_ST, <i>D</i>_EST and <i>H</i>_o through time (generations) estimated from computer simulations for different migration rates after a ‘highway’ replaces at generation 500 a previous scenario of panmixia and assuming a multigeneration <i>Ne</i> of 54 for each roadside site.

<p>For each migration rate (m), the plots in the left panel show the evolution of the parameters through the simulation and the plots in the right panel show a detail of the simulations for the period in which the ‘highway’ has been introduced (apricot areas in the left plots). The 5–95 percentile envelopes (999 replicates for each migration rate value) are shown in light coral. In the right plots, the blue circles represent observed values, which are placed to the right of generation 500 according to the highway’s age and assuming a generation time of six months [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151500#pone.0151500.ref088" target="_blank">88</a>].</p

Comparison of genetic patterns for the three highways obtained from <i>F</i>_ST using ENA, <i>G”</i>_ST, <i>D</i>_EST and <i>D</i>_c.

<p>Green and orange lines represent the genetic differentiation observed between, respectively, sampling lines on opposite roadsides and on the same roadside. Dots represent mean values and limits are 95% confidence intervals.</p