Forest Fragmentation and Developmental Stability of Wood Mice Apodemus sylvaticus: A Food-Mediated Effect?

Generalist mice are key species for the long-term dynamics of fragmented forests due to their dual role as seed dispersers or predators of the dominant trees. Wood mice, Apodemus sylvaticus, usually act as a net predator in woodlots due to higher winter densities and earlier winter reproduction than in forests. Here we analyze the recruitment expectations of young mice born in woodlots in relation to food availability through an index of developmental stability that combined values of fluctuating asymmetry (FA) for six traits of the lower mandibles. FA was measured in young and adult mice caught at the end of the winter in control woodlots, food-supplemented woodlots and in a nearby large forest. Despite low sample sizes (n = 9 for young and n = 74 for adults), FA in young mice born in control woodlots were significantly higher than in those from food-supplemented woodlots and the forest and in all adults. Food limitation in woodlots was thus associated with increased developmental instability of young mice, but it had no effect on adults. Instability likely reduced the survival prospects of young mice through increased mortality, and this should be compensated by yearly recolonization of woodlots by adults from the agricultural matrix in autumn and winter. Future work analyzing mechanisms suggested here but using non-lethal methods will be important to clarify the impacts of FA on the population dynamics of wood mice.

Environmental determinants of Anaplasma phagocytophilum infection in cattle using a kernel density function

The study of vector-borne zoonotic diseases often relies on partial data, because of the constraints associated with observing various elements of the transmission cycle: the pathogen, the vector, the host - wild or domestic. Each angle comes with its own practical challenges, leading to data reflecting poorly either on spatial or temporal dynamics, or both. In this study, we investigated the effect of landscape on the presence of bovine ehrlichiosis infection in Walloon cattle. This disease is transmitted to cattle through the bite of a tick infected by the bacterium Anaplasma phagocytophilum. The first case of bovine ehrlichiosis in the southern region of Belgium (Wallonia) was detected in 2005 and the high seroprevalence found in herds suggests that the disease is endemic. The presence of antibodies of A. phagocytophilum in one cow selected in each of 1445 herds in 2010 and 2011 was detected using indirect immunofluorescence. Samples were geolocated at the farm. However, the precise location of infection remains uncertain. To account for the data sparsity, we elaborated a spatial index for the intensity of the presence of seropositive animals, based on a non-parametric kernel density estimation. We examined this index with the landscape surrounding the pastures, using multiple regressions. Landscape factors were selected using a conceptual framework based on the ecological resources needed for the transmission cycle of A. phagocytophilum. Results suggest that our spatial index adequately reflected infection presence in cattle in Wallonia, which was highest in central regions, corresponding to more forested and fragmented landscapes. We noticed that the presence of large hosts, wild or domestic, as well as the composition and configuration of the landscape of the pasture, influenced the capacity of the pasture to support the presence of bovine ehrlichiosis in Walloon herds. This is consistent with the ecology of A. phagocytophilum and current knowledge about risk factors of tick-borne diseases in cattle at the regional scale. The nature of the kernel density index, based on uncertainties over the location of cases positive to A. phagocytophilum, reflected the infectiousness profile at the landscape and not at the pasture level. Results also highlighted that the effects of some environmental variables remain, even when considering the different agro-geographic regions of Wallonia, which present contrasted landscapes and different levels of intensity of A. phagocytophilum infection. The kernel density index is a useful tool to help veterinary practitioner to quickly target areas where A. phagocytophilum infection is likely.

Small mammal responses to long-term large-scale woodland creation: the influence of local and landscape-level attributes

Habitat loss and fragmentation greatly affect biological diversity. Actions to counteract their negative effects include increasing the quality, amount and connectivity of seminatural habitats at the landscape scale. However, much of the scientific evidence underpinning landscape restoration comes from studies of habitat loss and fragmentation, and it is unclear whether the ecological principles derived from habitat removal investigations are applicable to habitat creation. In addition, the relative importance of local- (e.g., improving habitat quality) vs. landscape-level (e.g., increasing habitat connectivity) actions to restore species is largely unknown, partly because studying species responses over sufficiently large spatial and temporal scales is challenging. We studied small mammal responses to large-scale woodland creation spanning 150 yr, and assessed the influence of local- and landscape-level characteristics on three small mammal species of varying woodland affinity. Woodland specialists, generalists, and grassland specialists were present in woodlands across a range of ages from 10 to 160 yr, demonstrating that these species can quickly colonize newly created woodlands. However, we found evidence that woodlands become gradually better over time for some species. The responses of individual species corresponded to their habitat specificity. A grassland specialist (Microtus agrestis) was influenced only by landscape attributes; a woodland generalist (Apodemus sylvaticus) and specialist (Myodes glareolus) were primarily influenced by local habitat attributes, and partially by landscape characteristics. At the local scale, high structural heterogeneity, large amounts of deadwood, and a relatively open understory positively influenced woodland species (both generalists and specialists); livestock grazing had strong negative effects on woodland species abundance. Actions to enhance habitat quality at the patch scale focusing on these attributes would benefit these species. Woodland creation in agricultural landscapes is also likely to benefit larger mammals and birds of prey feeding on small mammals and increase ecosystem processes such as seed dispersal.

Stressful living in lower-quality habitats? Body mass, feeding behavior and physiological stress levels in wild wood mouse populations

Wild populations are continuously subjected to changes in environmental factors that pose different challenges. Body condition and hormones have been commonly used as health indicators due to their potential correlation with fitness. In the present study, we analyzed whether habitats of different quality influenced body mass, food intake and physiological stress levels in wild wood mice (Apodemus sylvaticus). Field work was seasonally carried out in Holm oak woods and pine forests in central Spain. A total of 93 wood mice from 4 different populations (2 per habitat type) were live-trapped. From each captured individual we noted body mass and food intake, measured as the amount of bait remaining in each trap. The physiological stress levels were measured non-invasively in collected fresh feces by quantifying fecal corticosterone metabolites (FCM) with a 5a-pregnane-3ß,11ß, 21-triol-20-one enzyme immunoassay. Wood mice abundances decreased from spring to summer, were higher in Holm oak woods than in pine forests and also resulted in different age-class distribution between both habitats. Individuals inhabiting pine forests showed a lower body mass and increased food intake, probably because of the comparatively lower food quality and availability in this habitat. Furthermore, these individuals showed increased physiological stress levels, likely due to the lower quality habitat in relation to both food and vegetation cover availability. Overall, besides affecting local wood mouse abundance, our study underscores the effect of habitat quality on body mass, food intake and the endocrine stress response. Considering the wood mouse's pivotal position in ecosystems, these results could help in the understanding of environmental traits hampering the viability of wild populations.

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.

Species-Specific Responses of Carnivores to Human-Induced Landscape Changes in Central Argentina

The role that mammalian carnivores play in ecosystems can be deeply altered by human-driven habitat disturbance. While most carnivore species are negatively affected, the impact of habitat changes is expected to depend on their ecological flexibility. We aimed to identify key factors affecting the habitat use by four sympatric carnivore species in landscapes of central Argentina. Camera trapping surveys were carried out at 49 sites from 2011 to 2013. Each site was characterized by 12 habitat attributes, including human disturbance and fragmentation. Four landscape gradients were created from Principal Component Analysis and their influence on species-specific habitat use was studied using Generalized Linear Models. We recorded 74 events of Conepatus chinga, 546 of Pseudalopex gymnocercus, 193 of Leopardus geoffroyi and 45 of Puma concolor. We found that the gradient describing sites away from urban settlements and with low levels of disturbance had the strongest influence. L. geoffroyi was the only species responding significantly to the four gradients and showing a positive response to modified habitats, which could be favored by the low level of persecution by humans. P. concolor made stronger use of most preserved sites with low proportion of cropland, even though the species also used sites with an intermediate level of fragmentation. A more flexible use of space was found for C. chinga and P. gymnocercus. Our results demonstrate that the impact of human activities spans across this guild of carnivores and that species-specific responses appear to be mediated by ecological and behavioral attributes.

Marine resources subsidize insular rodent populations in the Gulf of California, Mexico

Inputs of energy and nutrients from one ecosystem may subsidize consumers in adjacent ones, with significant consequences for local communities and food webs. We used stable isotope and faecal pellet analysis to quantify use of ocean-derived resources by small mammals on islands in the Gulf of California, Mexico. Rodents were live-trapped on grids originating near shore and extending 125-200 m inland to evaluate the extent to which rodents transport marine nutrients inland, and to determine whether marine foods subsidize island populations, permitting higher densities than would be possible based on terrestrial resources alone. Both faeces and stable carbon and nitrogen isotopes revealed that omnivorous mice (Peromyscus maniculatus) consume ocean-derived prey, including littoral and supralittoral invertebrates, and that their diets differed markedly from those of granivorous rodents (Chaetodipus rudinoris). On a small, seabird roosting island, marine prey were important in the diet of mice regardless of their proximity to shore, underscoring the pervasive influence of the ocean on small islands with relatively large coastline area. On a large island, however, consumption of marine foods declined sharply > or =50 m from shore, which suggests that mice are poor conduits of inland movement of energy and nutrients from the sea. Marine resources seemed to act as subsidies for omnivorous rodents: more P. maniculatus were captured near shore than farther inland and there was an inverse relationship between island area and rodent abundance, suggesting that small islands with large amounts of marine inputs support the highest population densities. Patterns of local and island-wide abundance of P. maniculatus are likely the result of several interacting factors, including frustrated dispersal, competition with C. rudinoris, and the absence of predators. We speculate, however, that the availability of marine resources allows P. maniculatus to reach high densities and to persist on small islands in the Gulf despite low and unpredictable terrestrial productivity. Spatial trophic subsidies thus provide a possible mechanistic explanation for the widely reported inverse relationship between population density and island or habitat area.

Factors affecting wild boar (Sus scrofa) occurrence in highly fragmented Mediterranean landscapes

This paper is an analysis of the effects of forest fragmentation on wild boar (Sus scrofa) occurrence in coarse-grained fragmented landscapes (<20% forest–scrubland cover on a landscape scale; N = 140 forest fragments, four regions) in central Spain. Occurrence was examined in relation to forest size, isolation, habitat quality, and region. Wild boar occurrence was mainly explained by the location of the forest fragments on the northern or southern plateau. Wild boars were more abundant on the northern plateau than on the southern plateau. In addition, wild boars are more frequent in large forest fragments adjacent to other large forests near mountains or riparian woodlands. The percent presence of wild boars in fragments varied among the four regions sampled (regional effect). Although wild boars occurred more frequently in large than in small forests, this pattern was less pronounced than that found in badgers (Meles meles), roe deer (Capreolus capreolus), and stone martens (Martes foina) and similar to that found in red foxes (Vulpes vulpes). The spatial distribution of wild boars may be affected by forest fragmentation despite their typical generalist life-history traits and potential use of agricultural areas as food habitats. These results support the idea that landscape pattern (degree of fragmentation and grain pattern) may be a determinant of species' abundance and distribution in fragmented landscapes.

Factors determining "gaps" in the distribution of a small carnivore, the common genet (Genetta genetta), in central Spain

We studied the pattern of distribution of the common genet (Genetta genetta) in areas in mountains and plains of central Spain, in the middle of the range of the species. We evaluated the role of temperature, rainfall, and habitat features in determining the ecological limits of genet distribution. Genets were very scarce on plateaux and the upper parts of the mountains, but were widely distributed in lower mountain areas. Genets were present in areas with abundant shrub cover, high mean of the mean minimum temperature and high mean of mean winter temperatures. Survey routes at the same altitude (<1000 m) in the mountains (genets abundant) and on the plateaux (genets very scarce) also differed in some of these variables, with low values on the plateaux for shrub cover, mean of the mean minimum temperatures, mean of the mean winter temperatures, and annual rainfall. Genets originated in Africa, therefore they are probably ill-adapted (morphologically and physiologically) for the cold conditions predominating in most of central Spain. Their preference for shrubby habitats may be linked to a greater availability of food and low risk of predation. Intermediate levels of rainfall may be correlated with higher temperatures, the key factor hypothesized to affect the distribution of this species. The distribution of the common genet fits a multimodal model, with peaks (presence) and valleys (absence) in the middle of its range, indicating that location in a particular part of the range is not a prior indicator of habitat suitability for the species.