Clara Grilo

Inter-Individual Variability of Stone Marten Behavioral Responses to a Highway

Efforts to reduce the negative impacts of roads on wildlife may be hindered if individuals within the population vary widely in their responses to roads and mitigation strategies ignore this variability. This knowledge is particularly important for medium-sized carnivores as they are vulnerable to road mortality, while also known to use available road passages (e.g., drainage culverts) for safely crossing highways. Our goal in this study was to assess whether this apparently contradictory pattern of high road-kill numbers associated with a regular use of road passages is attributable to the variation in behavioral responses toward the highway between individuals. We investigated the responses of seven radio-tracked stone martens (Martes foina) to a highway by measuring their utilization distribution, response turning angles and highway crossing patterns. We compared the observed responses to simulated movement parameterized by the observed space use and movement characteristics of each individual, but naïve to the presence of the highway. Our results suggested that martens demonstrate a diversity of responses to the highway, including attraction, indifference, or avoidance. Martens also varied in their highway crossing patterns, with some crossing repeatedly at the same location (often coincident with highway passages). We suspect that the response variability derives from the individuals familiarity of the landscape, including their awareness of highway passage locations. Because of these variable yet potentially attributable responses, we support the use of exclusionary fencing to guide transient (e.g., dispersers) individuals to existing passages to reduce the road-kill risk.

Assessing genetic structure in common but ecologically distinct carnivores: the stone marten and red fox

The identification of populations and spatial genetic patterns is important for ecological and conservation research, and spatially explicit individual-based methods have been recognised as powerful tools in this context. Mammalian carnivores are intrinsically vulnerable to habitat fragmentation but not much is known about the genetic consequences of fragmentation in common species. Stone martens (Martes foina) and red foxes (Vulpes vulpes) share a widespread Palearctic distribution and are considered habitat generalists, but in the Iberian Peninsula stone martens tend to occur in higher quality habitats. We compared their genetic structure in Portugal to see if they are consistent with their differences in ecological plasticity, and also to illustrate an approach to explicitly delineate the spatial boundaries of consistently identified genetic units. We analysed microsatellite data using spatial Bayesian clustering methods (implemented in the software BAPS, GENELAND and TESS), a progressive partitioning approach and a multivariate technique (Spatial Principal Components Analysis-sPCA). Three consensus Bayesian clusters were identified for the stone marten. No consensus was achieved for the red fox, but one cluster was the most probable clustering solution. Progressive partitioning and sPCA suggested additional clusters in the stone marten but they were not consistent among methods and were geographically incoherent. The contrasting results between the two species are consistent with the literature reporting stricter ecological requirements of the stone marten in the Iberian Peninsula. The observed genetic structure in the stone marten may have been influenced by landscape features, particularly rivers, and fragmentation. We suggest that an approach based on a consensus clustering solution of multiple different algorithms may provide an objective and effective means to delineate potential boundaries of inferred subpopulations. sPCA and progressive partitioning offer further verification of possible population structure and may be useful for revealing cryptic spatial genetic patterns worth further investigation.

Optimal planning to mitigate the impacts of roads on multiple species

Common worldwide and encroaching on even the most remote locations, roads negatively affects wildlife through habitat loss, fragmentation and direct mortality. Reducing these effects requires mitigation, including wildlife crossing structures and fencing. However, mitigation measures are expensive and vary in their success level, especially when constructed to meet the needs of several species. Moreover, mitigation planning rarely considers the needs of multiple species. As funds are limited, deciding where and how to act for the greatest return on investment is crucial. Combining decision theory with a metapopulation model, we determined the most cost-effective actions mitigating the effects of roads on multiple species. The model is illustrated with two sets of species with varying of life-history traits, from a diversity of taxonomic groups. We tested the cost-effectiveness of spatially explicit combinations of three management options for each road section: (a) no mitigation, (b) fences without wildlife crossings, and (c) fences combined with wildlife crossings. We explored the trade-offs between each populations probability of persistence and total mitigation cost, first on a per-species basis and then considering all species. We then tested the cost-effectiveness of different planning strategies: (a) single species, (b) two types of focal species based on different life-history traits, and (c) comprehensive multispecies planning. Planning for the needs of all species at the same time (multispecies strategy) maximizes the number of persisting species and provides the most robust and cost-effective planning strategy, while single-species strategies were found to be inefficient. However, basing decisions on the focal species with the largest home range can provide reasonably cost-effective results, but should be considered only when there is not enough time or money to collect the necessary information to perform a multispecies analysis. Synthesis and applications. Our model can be adapted to most road mitigation problems. It illustrates that the needs of multiple species should be considered to plan a cost-effective road mitigation system. However, when resources are limited to plan for all species, those with larger home ranges should be used as reasonable proxies for other species.

Railway Disturbances on Wildlife: Types, Effects, and Mitigation Measures

In this chapter, we review the level of disturbance caused by railways due to noise and vibration, air, soil and water pollution, and soil erosion. There is evidence that soil and hydrology contamination may affect vegetation and aquatic fauna while noise can affect terrestrial vertebrates. In fact, noise, light, and vibration due to railways have been observed to reduce the abundance and richness of some insects, amphibians, and birds, and to cause avoidance behaviour on predators. Interestingly, reptiles, some bird species, small mammals, and large mammals seem to ignore rail traffic and benefit from the vegetation planted in the railway verges that provide food and shelter. Some engineering structures have been implemented to reduce the effects of railway disturbance: rail fastenings, rail dampers, under-sleeper pads, and noise barriers are applied to minimize noise and vibration; washing with water and cleaning the ballast are used to mitigate soil pollution; and grass plantation, the use of gypsum and application of compost/mulch coverage, are applied to control soil erosion.