title: An investigation into the factors influencing hedgehog (Erinaceus europaeus) occupancy throughout rural and urban Britain
Creators: name: Williams, Benjamin Merth
Publisher: name: University of Reading
Year: 2022

description: Wildlife conservation and management require robust field data in order to formulate appropriate evidence-based management actions. Yet collecting such data can be challenging. For example, monitoring programmes in the UK indicate that populations of West European hedgehogs (Erinaceus europaeus) have declined markedly. However, these programmes are potentially associated with a range of limitations that raise questions about the robustness of estimated trends and their usefulness in determining underlying causal factors. In this study, the efficacy of footprint-tunnels in conjunction with occupancy analysis was examined as a method for monitoring the presence / absence of hedgehogs in both urban and rural landscapes. Overall, 261 sites in England and Wales, and 219 gardens in Reading, Berkshire, were surveyed. Given the limited availability of funding for conservation monitoring in the UK, such that any future monitoring would most likely have to be conducted as a “citizen science” project, surveying was conducted primarily by members of the general public. False-absence error rates in both landscapes were extremely low (rural: ≤ 0.8%; urban: 0.1 - 0.4%), indicating the technique was very reliable. However, occupancy rates were also low: hedgehogs were only detected at 21% of rural sites and in 32-40% of gardens. Rural hedgehog occupancy was negatively affected by badger (Meles meles) sett density and positively influenced by the built environment, although hedgehogs were also absent from 71% of sites without badger setts. Collectively, this indicates that hedgehogs are absent from large areas of the rural landscape. Garden occupancy was negatively influenced by the presence of badgers, but not significantly. No other within- or outside-garden factors affected hedgehog presence in residential gardens. As such, it is not clear what promotes the use of gardens by hedgehogs in urban areas. However, inter-annual patterns of garden use were very consistent: hedgehogs were and were not detected in 52% and 27% of gardens (N=60) surveyed in two separate years, respectively. Expanding road networks in countries such as the UK potentially exert two important effects on hedgehog populations: (i) direct mortality and / or (ii) barrier effects to movement. Analysis of the locations of road-killed hedgehogs from Suffolk (Eastern England) indicated that casualties were clustered at all spatial scales and concentrated in urban areas. In both urban and rural landscapes, hedgehogs were more likely to be killed on roads with a speed limit ≤ 30 mph, potentially indicating an association with areas of human habitation. Hedgehog carcasses in urban areas were also positively associated with the presence of parked cars and proximity to road junctions; rural hedgehog carcasses were positively associated with the presence of neighbouring hedgerows / woodland edges. These results suggest that road signs may be one possible means for helping reduce the numbers of road casualties. Using a panel of microsatellites to investigate hedgehog population structure showed no discrete genetic clusters in Southern England. The results suggest good gene flow between individuals with no absolute barriers to movement. Deterministic matrix population modelling indicated that current estimates of key demographic parameters in the literature do not generate patterns of decline in hedgehog populations observed in ongoing monitoring programmes. This highlights an urgent need for further research into hedgehog population demographics. Small changes c. 5-10% in adult or juvenile survival are likely to enable hedgehog population growth. In summary, hedgehogs appear to have a negative relationship with badgers and be positively associated with urban areas. Work here highlights several areas of concern for hedgehog conservation and expedited work is needed to address this; however, with successful conservation initiatives the hedgehog population should be able to recover relatively rapidly.