Sheltered building edges may facilitate hedgehog dispersal in urban landscapes
Hedgehogs (Erinaceus europaeus) are an illuminating indicator species that reflects the quality and connectivity of urban habitats. Previous research suggests that edge habitats play a remarkable role in landscape permeability for hedgehogs when predators exist. Edge-refuging behaviours observed in semi-natural habitats have rarely been recorded in building edges, and their impacts on hedgehog movement are unclear. Our goal is to quantify the relative resistance with respect to behaviour patterns in built environments. However, building edges exceed the measuring accuracy of biotelemetry. Moreover, positions tracked by biotelemetry offer little behavioural context and require a simultaneous visual sighting. Direct observations provide sufficient details in complex landscapes although they are prone to biases by human presence. Using six translocated hedgehogs, we performed direct observations for 41 nights in April to June 2012-2013 to record the trajectories and habitat occurrences on nine landcovers at 2.5, 5 or 10 min intervals on university campuses. We classified the trajectories into six behavioural patterns by visual interpretation, i.e. foraging, exploring, surveying, gap-crossing, inbound and outbound refuging. We computed the (1) frequency of occurrences in movement range; (2) speed distribution of each behavioural pattern; (3) landscape entropy in each behaviour pattern; and (4) behavioural entropy on each landcover.
Three translocated hedgehogs were tracked for consecutive 6-10 nights and the remaining tracked for 1-3 nights. Gap-crossing is the speediest pattern (mean 18.4±3.0 m/min), foraging and outbound refuging are the lowest (mean 1.7±0.7m/min), and exploring (mean 5.6±1.6 m/min) and surveying (mean 8.7±2.2 m/min) are the intermediates. All speed distributions are well approximated as lognormal distributions and pass the Kolmogorov-Smirnov test (p<0.05). The speed distribution of the aggregate behaviour consists with that of the exploring, suggesting the movement of a translocated hedgehog is largely exploratory. Behavioural patterns are distinguishable by speed distributions except for the foraging and refuging, which are otherwise identifiable by landscape entropy. The ranking of landscape entropy, in descending order, is surveying, gap-crossing, outbound refuging, exploring, foraging, and inbound refuging. Using behavioural entropy, we show that dispersing hedgehogs are inclined to use copses, building edges, shrubs and hedgerows, weeds with sparse woods, and abandoned yards, but avoid using lawns, streets and pavements. Building edges encompassing holes in buildings, climbers against the walls, heaps at the corners, etc. are a notably underestimated habitat, which may function as innovative corridors in built environments.