Influence of solution chemistry on the solubility, crystallisability and nucleation behaviour of eicosane in toluene : acetone mixed-solvents

The interplay between the solution chemistry and crystallisability of eicosane in mixed toluene : acetone solutions is examined over the full compositional range from pure toluene to pure acetone, using a combination of polythermal crystallisation experiments and molecular modelling. Enthalpies of dissolution and mixing, as well as metastable zone widths increase with increasing acetone content, up to a mol fraction of 0.85 acetone, followed by a decrease in values to pure acetone solutions. Nucleation is found to occur via an instantaneous pathway for the pure solvent systems and also when toluene is in excess, in contrast to solutions where acetone is in excess, which are found to nucleate progressively. Rationalisation through molecular modelling highlights likely changes in the solution structure, whereby eicosane can be expected to be preferentially solvated by toluene, with this solvated cluster being surrounded by a ‘cage’ of acetone molecules. This proposed structure is consistent with a model whereby solute diffusion and hence clustering is hindered when acetone is in excess, decreasing the crystallisability of the solution and effecting a change in the mechanism of nucleation. However, above a critical acetone composition, the potential for complete toluene solvation is restricted and easier crystallisation is enabled

Reduced occupancy of hedgehogs (Erinaceus europaeus) in rural England and Wales: the influence of habitat and an asymmetric intra-guild predator

Agricultural landscapes have become increasingly intensively managed resulting in population declines across a broad range of taxa, including insectivores such as the hedgehog (Erinaceus europaeus). Hedgehog declines have also been attributed to an increase in the abundance of badgers (Meles meles), an intra-guild predator. The status of hedgehogs across the rural landscape at large spatial scales is, however, unknown. In this study, we used footprint tracking tunnels to conduct the first national survey of rural hedgehog populations in England and Wales. Single and two-species occupancy modelling was used to quantify hedgehog occupancy in relation to habitat and predator covariates. Hedgehog occupancy was low (22% nationally), and significantly negatively related to badger sett density and positively related to the built environment. Hedgehogs were also absent from 71% of sites that had no badger setts, indicating that large areas of the rural landscape are not occupied by hedgehogs. Our results provide the first field based national survey of hedgehogs, providing a robust baseline for future monitoring. Furthermore, the combined effects of increasing badger abundance and intensive agriculture may have provided a perfect storm for hedgehogs in rural Britain, leading to worryingly low levels of occupancy over large spatial scales

Biodiversity in urban gardens: assessing the accuracy of citizen science data on garden hedgehogs

Urban gardens provide a rich habitat for species that are declining in rural areas. However, collecting data in gardens can be logistically-challenging, time-consuming and intrusive to residents. This study examines the potential of citizen scientists to record hedgehog sightings and collect habitat data within their own gardens using an online questionnaire. Focussing on a charismatic species meant that the number of responses was high (516 responses were obtained in 6 weeks, with a ~ 50:50% split between gardens with and without hedgehog sightings). While many factors commonly thought to influence hedgehog presence (e.g. compost heaps) were present in many hedgehog-frequented gardens, they were not discriminatory as they were also found in gardens where hedgehogs were not seen. Respondents were most likely to have seen hedgehogs in their garden if they had also seen hedgehogs elsewhere in their neighbourhood. However, primary fieldwork using hedgehog ‘footprint tunnels’ showed that hedgehogs were found to be just as prevalent in gardens in which hedgehogs had previously been reported as gardens where they had not been reported. Combining these results indicates that hedgehogs may be more common in urban and semi-urban gardens than previously believed, and that casual volunteer records of hedgehogs may be influenced more by the observer than by habitat preferences of the animal. When verified, volunteer records can provide useful information, but care is needed in interpreting these data