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Competition arises when two co-occuring species share a limiting resource. Potential for competition is higher when species have coexisted for a short time, as it is the case for herbivores and livestock introduced in natural systems. Sheep, introduced in the late 19th century in Patagonia, bear a great resemblance in size and diet to the guanaco, the main native herbivore in Patagonia. In such circumstances, it could be expected that the two species compete and one of them could be displaced. We investigated spatial overlap and habitat selection by coexisting sheep and guanaco in winter and in summer. Additionally, we studied habitat selection of the guanaco in a control situation free from sheep, both in summer and winter. We also determined overlap between species in areas with different intensity of use (named preferred and marginal areas) in order to further detect the potential level of competition in the case of overlapping. Guanaco and sheep showed significantly different habitat preferences through all seasons, in spite of their spatial overlap at landscape scale. Additionally, the habitat used by guanaco was similar regardless of the presence or absence of livestock, which further indicates that sheep is not displacing guanaco where they coexist. These results suggest that habitat segregation between guanaco and sheep is due to a differential habitat selection and not to a competitive displacement process. Therefore, the potential for competition is considered low, contrary to what has been previously observed, although this could be a density-dependent result.

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.

Landscape disturbance by roads may increase abundance of prey in verges 20 (i.e., strips of terrain adjacent to roadways) or create other features that can attract carnivores 21 and expose them to a higher risk of mortality by vehicle collision. We studied a system that 36 linear transects within the study area, 18 along motorways and 18 in control zones ( Fig. 1). 119We defined control zones as those with the same habitat structure and ≥4 km from habitat effect. We double-checked transects for habitat similarity; first we inspected habitat . We calculated the index value as the sum of all pellets counted in each transect. 142We estimated a carnivore abundance index as the number of scats detected in each 143 transect (Long et al. 2008 of the raw data in each transect type followed the same pattern for almost all the taxa, with 240higher mean values in motorways than in control sites (Fig. 2). Global carnivore abundance 241 increased with rabbit abundance (β = 0.103 ± 0.044, P = 0.019) and carnivore abundance was 242 higher in motorway transects than control sites (β = 0.400 ± 0.175, P = 0.022). 243The red fox showed higher abundance in motorways (β = 0.469 ± 0.197, P = 0.017) 244 but no significant response to rabbit abundance (P = 0.129; Fig. 3). The non-synanthropic 245 species showed the opposite response, with abundances positively related to rabbit abundance 246(β = 0.119 ± 0.044, P = 0.007) but no differences in abundance due to the proximity of the 247 motorway (P = 0.084; Fig. 3). 248Cascading Effects: Rabbit Abundance, Carnivore Abundance, and Roadkills 255In the analyses for the global carnivore community, roadkills were positively and numbers. For carnivores related closely to prey abundance, high prey abundance in verges 275 creates a local cascading effect that leads to carnivore roadkills. 276The increased abundance of the global carnivore community near motorways is 277 probably due to higher fox abundance in these areas, as foxes comprised almost half of the 295On the other hand, our group of non-synanthropic carnivores followed a different carnivores that prey on them will follow rabbit distribution. we controlled for by conducting DNA analysis to assess the accuracy of scat identification. 332We controlled for other potential sources of bias by choosing areas that were comparable in 333 habitat characteristics, which can affect fecal persistence and scat detectability (Long et al. are necessary to make informed management decisions that favor conservation objectives. 364Understanding wildlife responses to human-modified landscapes provides us with better 365 knowledge of the communities and identifies which processes should be the focus of our 366 conservation efforts. 367 MANAGEMENT IMPLICATIONS 368When prey are abundant near motorways, carnivores increase their abundance in those areas. 369Higher abundances of carnivores were strongly related to higher mortality by vehicles. 370Therefore, the design and management of verges could be a key aspect for conservation of 371 wil...

Some small mammal species use road verges as a habitat for sheltering. As a result, their populations suffer mortality from roadkill in an unknown extent. We analysed the road mortality of small mammals and the population impact of roadkill on wood mouse along 1 year on a 4‐km motorway stretch. To account for potential bias in carcass sampling, we conducted walking surveys with the traffic interrupted and we performed three carcass persistence experiments to estimate total number of roadkills. The estimations were contrasted with previous studies and the population abundance on the road verges. The spatial pattern and the effects of seasonality and traffic volume on roadkill were analysed. We recorded 84 rodent carcasses with a mean carcass persistence of 6.65 days (SE = 0.41). The estimations of roadkill ranged between 190.2 and 238.3 individuals km−1 year−1, with a mean value close to a monthly 6 % mortality for the most common specie. Roadkill was more frequent during the hottest and driest months, and showed a unimodal relation with traffic peaking at 8100 vehicles day−1. A spatial aggregation of roadkill was detected with 80–190 m clustering. Our results suggest that, although rodents suffer greater roadkill mortality than previously reported, it affects a small percentage of the wood mouse population in our study area. This source of mortality is unlikely to affect population viability in the short term. Our results show that roadkill surveys should be specifically designed for small mammals to have a more accurate analysis of the effects of roadkill on their 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 5α-pregnane-3β,11β, 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 ecosystems.