Monitoring frequency influences the analysis of resting behaviour in a forest carnivore

Resting sites are key structures for many mammalian species, which can affect reproduction, survival, population density, and even species persistence in human-modified landscapes. As a consequence, an increasing number of studies has estimated patterns of resting site use by mammals, as well as the processes underlying these patterns, though the impact of sampling design on such estimates remain poorly understood. Here we address this issue empirically, based on data from 21 common genets radiotracked during 28 months in Mediterranean forest landscapes. Daily radiotracking data was thinned to simulate every other day and weekly monitoring frequencies, and then used to evaluate the impact of sampling regime on estimates of resting site use. Results showed that lower monitoring frequencies were associated with major underestimates of the average number of resting sites per animal, and of site reuse rates and sharing frequency, though no effect was detected on the percentage use of resting site types. Monitoring frequency also had a major impact on estimates of environmental effects on resting site selection, with decreasing monitoring frequencies resulting in higher model uncertainty and reduced power to identify significant explanatory variables. Our results suggest that variation in monitoring frequency may have had a strong impact on intra- and interspecific differences in resting site use patterns detected in previous studies. Given the errors and uncertainties associated with low monitoring frequencies, we recommend that daily or at least every other day monitoring should be used whenever possible in studies estimating resting site use patterns by mammals

Estimating how inflated or obscured effects of climate affect forecasted species distribution

Climate is one of the main drivers of species distribution. However, as different environmental factors tend to co-vary, the effect of climate cannot be taken at face value, as it may be either inflated or obscured by other correlated factors. We used the favourability models of four species (Alytes dickhilleni, Vipera latasti, Aquila fasciata and Capra pyrenaica) inhabiting Spanish mountains as case studies to evaluate the relative contribution of climate in their forecasted favourability by using variation partitioning and weighting the effect of climate in relation to non-climatic factors. By calculating the pure effect of the climatic factor, the pure effects of non-climatic factors, the shared climatic effect and the proportion of the pure effect of the climatic factor in relation to its apparent effect (r), we assessed the apparent effect and the pure independent effect of climate. We then projected both types of effects when modelling the future favourability for each species and combination of AOGCM-SRES (two Atmosphere-Ocean General Circulation Models: CGCM2 and ECHAM4, and two Special Reports on Emission Scenarios (SRES): A2 and B2). The results show that the apparent effect of climate can be either inflated (overrated) or obscured (underrated) by other correlated factors. These differences were species-specific; the sum of favourable areas forecasted according to the pure climatic effect differed from that forecasted according to the apparent climatic effect by about 61% on average for one of the species analyzed, and by about 20% on average for each of the other species. The pure effect of future climate on species distributions can only be estimated by combining climate with other factors. Transferring the pure climatic effect and the apparent climatic effect to the future delimits the maximum and minimum favourable areas forecasted for each species in each climate change scenario.Ministerio de Ciencia e Innovación and FEDER (project CGL2009-11316/BOS). D. Romero is a PhD student at the University of Malaga with a grant of the Ministerio de Educacio´n y Ciencia (AP 2007-03633

Road effects on demographic traits of small mammal populations

Recent studies have highlighted the positive effects of road verges on the abundance of small mammals. However, most of these studies occurred in intensively grazed or cultivated areas, where verges were the last remnants of suitable habitats, which could mask the true effects of roads on population traits. We analysed the effects of roads on small mammal populations living in a well-preserved Mediterranean forest. We used the wood mouse (Apodemus sylvaticus) as a model of forest-dwelling small mammals that probably are among the species most affected by road clearings. Our study compared populations in similar habitat areas with and without road influence. We assessed abundance, survival and temporary emigration using extended Pollock’s robust design capture-recapture models. Moreover, we analysed population turnover, sex ratio, age structure and body condition. We found that wood mouse abundance and body condition were lower at the road bisected area, whereas the remaining population traits were similar. This suggests that the reduced habitat availability and quality due to the physical presence of the road and verge vegetation clearing are the main drivers of demographic differences in wood mouse populations between areas. Nevertheless, our results also suggest that in high-quality habitats surrounding national roads, wood mouse populations present similar dynamics to others living in undisturbed areas, despite the decrease in abundance and body condition. Overall, the often-reported increased small mammal abundance in road surroundings should not be generalized independently of habitat quality or to other population traits

Living on the verge: are roads a more suitable refuge for small mammals than streams in Mediterranean pastureland?

The retention of natural habitat corridors is a useful and practical conservation tool that can attenuate the effects of habitat loss and fragmentation on wildlife. Linear structures may contribute to the conservation of biodiversity by providing additional habitats for smallfauna living in highly modified environments. We assessed the importance of road verges as refuge areas for small mammals, in highly intensified grazed pastures, within a Mediterranean landscape and compared the role of road verges as refuges with that of riparian galleries, which have been described as important shelter locations for small fauna. For this purpose, a small mammal trapping study was undertaken on two road verges and beside two small streams in southern Portugal. We captured 457 individuals of five different species, with Mus spretus the most common species captured, followed by Crocidura russula. Captures were 4.6-fold higher immediately beside both roads and streams than 12 m away in the surrounding matrix. Individuals captured in the matrix presented a smaller body size and lower body condition, suggesting that this suboptimal habitat is occupied mainly by subadults. M. spretus was 46% more abundant by roads than by streams, while C. russula was present in similar numbers in both habitats. M. spretus individuals were larger near streams but exhibited no difference in body condition between habitats. C. russula had a better body condition and slightly higher body lengths at roadsides. Our results show that roadside verges in intensively grazed Mediterranean landscapes act as important refuges and constitute equally vital habitats for small mammals as do riparian vegetation strips in landscapes where other suitable habitats are scarce