Young et al (2006) hedgehog abundance badger effects
Title: Abundance of hedgehogs (Erinaceus europaeus) in relation to the density and distribution of badgers (Meles meles), Journal of Zoology 269; 349-356. 2005
Authors: R.P. Young, J. Davison, I.D. Trewby, G.J. Wilson, R.J. Delahay & C.P. Doncaster
Country: UK (Midlands and south-western region)
Background to study
Badgers are a known predator of hedgehogs and compete with them for food, thus there is expected to be a spatial relationship between the two species resulting from both avoidance of badgers by hedgehogs, predation of hedgehogs by badgers and through competition for the same food resources. This study investigates hedgehog abundance and use of spatial refugia within rural and suburban habitats in relation to indices of badger density and distribution obtained from surveys conducted as part of the Randomised Badger Culling Trial (RBCT).
- Hedgehogs occurrence and density within spatially independent amenity grassland (suburban) and pasture (rural) habitat was estimated in relation to badger density (number of sett and latrines) at a local and regional scale.
- Hedgehogs were surveyed between mid-June and mid-September within 23 amenity grasslands and 82 pasture fields across 10 RBCT treatment areas in using three replicated spotlight transects. Encountered individuals were uniquely marked using heat-shrink plastic tubes over individual spines and re-released.
- Badger activity within the fields was determined by the encounter of individuals during spotlight surveys and the presence of field signs (latrines, setts, runs, tracks and snagged hair).
- Badger density was estimated using latrine and sett location data obtained from Defra badger surveys which involved walked transects that had been carried out within one year prior to this study.
- Badger sett density was used as an index of badger abundance locally (within 500m of each survey field) and regionally (within 2km of each survey field) and were higher than the threshold for hedgehog occurrence previously predicted by Micol et al (1994).
- Hedgehogs were almost completely limited to suburban amenity grassland where 44 individuals were observed across 61% of surveyed fields at a mean relative density of 1.54+44 ha-1. Conversely, hedgehogs were only recorded in 3.7% of pasture fields at a mean density of 0.09+0.07ha-1.
- Mean regional badger main sett and all sett density was 0.81 and 6.19 km-2 respectively, around amenity grassland and 0.72 and 6.56 km-2 respectively around pasture fields.
- Local sett density and distance to nearest badger activity were the best indicators of badger activity in both habitat types.
- Habitat type and regional sett density were significant factors explaining hedgehog occurrence and a negative association between the occurrence of hedgehogs and regional sett density was observed.
- The mean predicted probability of hedgehog occurrence in amenity grassland was 62% and sharply declined as sett density increased. High sett density areas of over 10 setts km-2 reduced the probability of hedgehog occurrence to 33%.
- The mean predicted probability of hedgehog occurrence in pasture fields was 4.4% and when the number of badger setts was below 2 setts km2, the probability of hedgehog occurrence was 10%.
- Hedgehog abundance in amenity grassland decreased as regional sett density in the surrounding area increased with an estimated 3 hedgehogs ha-1 at very low sett density and less than 0.5 ha-1 when badger setts were above 10 setts km-2. No significant influence of local sett density on hedgehog abundance.
Key messages to landowners and managers derived from these results
- Amenity grassland provides refugia for hedgehogs from badgers that often avoid suburban areas for foraging. Management of amenity grassland for hedgehogs is recommended, particularly in areas where badger density is high.
- Hedgehogs in rural pasture land are limited by predation by badgers and high badger densities could result in a loss of hedgehogs from these areas.
- Distribution and habitat suitability surveys should account for badger presence and activity.