Carcass persistence and detectability : reducing the uncertainty surrounding wildlife-vehicle collision surveys

Carcass persistence time and detectability are two main sources of uncertainty on roadkill surveys. In this study, we evaluate the influence of these uncertainties on roadkill surveys and estimates. To estimate carcass persistence time, three observers (including the driver) surveyed 114km by car on a monthly basis for two years, searching for wildlife-vehicle collisions (WVC). Each survey consisted of five consecutive days. To estimate carcass detectability, we randomly selected stretches of 500m to be also surveyed on foot by two other observers (total 292 walked stretches, 146 km walked). We expected that body size of the carcass, road type, presence of scavengers and weather conditions to be the main drivers influencing the carcass persistence times, but their relative importance was unknown. We also expected detectability to be highly dependent on body size. Overall, we recorded low median persistence times (one day) and low detectability (<10%) for all vertebrates. The results indicate that body size and landscape cover (as a surrogate of scavengers' presence) are the major drivers of carcass persistence. Detectability was lower for animals with body mass less than 100g when compared to carcass with higher body mass. We estimated that our recorded mortality rates underestimated actual values of mortality by 2±10 fold. Although persistence times were similar to previous studies, the detectability rates here described are very different from previous studies. The results suggest that detectability is the main source of bias across WVC studies. Therefore, more than persistence times, studies should carefully account for differing detectability when comparing WVC studies

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Taha Toros Arşivi, Dosya No: 97-Cafer Bate

Conservation and Management of the Habitats of Two Relict Butterflies in the Belgian Ardenne: Proclossiana eunomia and Lycaena helle

Habitat preservation and restoration are crucial for species conservation and to tackle its main challenges. In many cases, this implies management actions, especially for seminatural ecosystems. We address here the question of management actions suitable for maintaining viable populations of two relict butterfly species inhabiting wet meadows and peat bogs in the Belgian Ardenne: the bog fritillary Proclossiana eunomia and the violet copper Lycaena helle. Habitat loss due to natural vegetation succession towards forest can be prevented either by mowing (traditional way of management) or by extensive grazing (with cattle or horses). Results from field studies and experiments conducted on several sites in the Belgian Ardenne led to two conclusions. Mowing can strongly affect the populations of both species, the impact being particularly pronounced on larval stages due to the removal of grass tussocks and the export of hay containing host plant on which caterpillars feed. Grazing also has a negative effect on both species, with adult density being lower on grazed biotopes compared to abandoned ones. However, the negative impact is more limited for grazing than for mowing. As both management methods have more or less pronounced negative impacts on populations of these two butterfly species, they should be applied with caution. We suggest that mowing should be applied in long-term rotation, with the preservation of sufficient refuge areas every year, and that grazing should be applied in late summer, every other year, with a low stocking rate (< 0.2 LU/ha/year). More particularly, to ensure their effectiveness in maintaining a favorable state, both the biotope and the associated populations using it as their habitat, managementactions must be designed according to the species habitat requirements, and adapted to carefully monitor their implementatio