Hubert et al (2011) hedgehog urban rural density compared
Title: Ecological factors driving the higher hedgehog (Erinaceus europaeus) density in an urban area compared to the adjacent rural area, Landscape and Urban Planning 103; 34-43. 2011
Authors: P. Hubert, R. Julliard, S. Biagianti & M-L, Poulle
Background to study
A study determining whether natural and anthropogenic food availability and risk of predation by badgers influences the density and reproductive rates of hedgehogs.
- The density of hedgehogs was estimated using distance sampling methods on 43 line-transects within a 41 km2 study area in north eastern France. Survey transects were 500 m in length, with one per km2 and followed a well defined track or road. Six transects were located within an urban area comprised of at least 20 settlements and dominated by lawn habitat (n = 6) and the remaining were within a rural area which comprised of four main habitat types (pasture, arable, meadow and forest).
- Transects were walked monthly from June to October 2006 and from March to October 2007 to detect the presence of hedgehogs using infrared binoculars (maximum range of 250 m).
- All hedgehogs detected were captured, their weight, sex and age (juveniles <600 g during summer sampling and adults >1 kg in autumn sampling) determined and each individuals was marked using six plastic covered tubes glued to the spines and with a subcutaneous microchip.
- The abundance of earthworms and arthropods per habitat type was determined by sampling five sites per habitat, three times during the hedgehog’s activity period. Earthworms were sampled using standardised formalin method and arthropods were sampled using Barber pitfall traps.
- Anthropogenic food availability was estimated using an index which combined domestic cat counts per hedgehog survey transect and number of gardens located within 100m either side of each transect.
- Predation risk was estimated for each transect as the distance from nearest badger sett.
- Regression analyses was used to explore factors that influence the number of hedgehogs observed per transect (density) and the proportion of juveniles to adult females encountered (recruitment rate).
- 127 hedgehogs were captured from a survey effort of 516 transects (mean detection distance of 44 m) of which the majority (79) were adults, 32 were young individuals and 16 were of unknown age.
- 70% of hedgehogs were detected on lawns, 14% in pastures and the remaining were detected on paths, arable land and in meadows. No hedgehogs were observed in forest habitat.
- Over 25% of adults were recaptured in both urban and rural areas but only 14% and 0% of young hedgehogs were recaptured in urban and rural areas respectively.
- Significant differences in hedgehog population density by habitat was observed with hedgehog density in urban areas (35/km-2) being 9 times higher than in rural areas (4/km-2).
- Arthropod, but not earthworm biomass/transect was significantly higher in rural areas than in urban areas, whilst anthropogenic food availability was significantly higher in urban areas than in rural areas.
- Distance to badger setts was significantly smaller in rural than in urban areas and this
- Increases in anthropogenic food availability and earthworm biomass per transect significantly increased the abundance of hedgehogs and this effect did not vary between urban and rural areas.
- Recruitment was significantly influenced by arthropod biomass and predation risk with areas that had higher arthropod biomass and located further from badger setts having the highest proportion of young per adult. However the distance from badger setts had a positive influence in the rural areas only.
Key messages to landowners and managers derived from these results
- To maintain viable and diverse prey communities for securing hedgehog survival and recruitment in urban areas, management plans that create/maintain structural diversity and connectivity (via green roofs, rain gardens, urban trees) amongst urban green space and within new urban development’s is recommended.
- Stewardship schemes that include low input field margins and hedgerows should be encouraged in a) rural areas to increase their suitability for hedgehogs and b) on farms surrounding urban areas as this may help increase arthropod diversity and biomass and thus the diversity of prey for hedgehogs in urban areas.