Doncaster et al (2001) hedgehog environmental correlates dispersal
Title: Field test for environmental correlates of dispersal in hedgehogs Erinaceus europaeus, Journal of Animal Ecology 70; 30-46. 2001
Authors: C.P. Doncaster, C. Rondinini & P.C.D. Johnson
Background to study
An experimental study investigating the dispersal, exploration, linear habitat use and and orientation of tagged hedgehogs released into favourable and unfavourable habitat to identify dispersal behaviour and thus the probable connectivity or isolation of local populations.
- 30 adult hedgehogs fitted with radio-transmitters were released sequentially (every two days) into five spatially idependent unfavourable sites including four in mixed pasture and arable farmland and one in urban. All sites were deemed unoccupied by hedgehogs, were within 0.5 and 2km of hedgehog occupied habitat, had a local food source and were >8 km from each hedgehogs original home range.
- 19 and 10 hedgehogs were released simultaneously into two favourable sites supporting a substantial hedgehog population where similar numbers had been removed to avoid density increase effects.
- The movements of 20 unmanipulated hedgehogs in an additional three sites were used as a control.
- All movements were monitored until areas became occupied for >5 days (~20 days) and involved obtaining one day time fix and locating and weighing each individual nightly.
- Dispersal and exploration was measured using minimum convex polygons (MCP), distance moved between each fix, maximum width of MCP, speed moved and total distance moved.
- Use of linear features was measured by calculating the nearest edge, road, large road and urban area to each fix obtained and was assessed in relation to the habitat type in which each fix was located.
- Orientation of translocated hedgehogs was measured by comparing their observed trajectory against simulated random trajectories.
- Use of different habitat types (urban, pasture, woodland, arable) was also assessed and compared to random simulated locations to measure preferential habitat use during dispersal.
- Unfavourable habitat releases resulted in the fatality of two hedgehogs crossing roads and six predations.
- No two hedgehogs followed the same route suggesting exploratory movements and movement behaviours were highly variable, ranging from true dispersal, through to nomadic floating and excursion away from and then returning to their release point. No substantial loss in weight was recorded.
- All treatments yielded a non-random association to habitat types and those released into unfavourable habitat showed a significant preference for urban and along with the control individuals avoided arable.
- All treatment groups had a lower % of fixes >90 m from linear or urban areas suggesting avoidance of open habitat and individuals released in unfavourable habitat were attracted to edge habitat and roads.
- Hedgehogs released into unfavourable habitat had significantly larger MCP’s (mean 92.2 ha) than the control group, moved significantly faster speeds (mean 334 m/day) and travelled a significantly further distance overall (mean 6.54km) than individuals released into favourable habitat and the control group.
- Significantly more males than females explored away from their release points however females were capable of moving just as far as males.
- Hedgehogs did not always settle in the closest habitat that supported a local population and would pass through suggesting some form of density dependence.
Key messages to landowners and managers derived from these results
- Hedgehogs are capable of long distance dispersal (>4 km) and thus populations located within this range are unlikely to be isolated.
- Habitat edges, particularly roads and hedgerows are utilised as dispersal corridors by hedgehogs thus management activities should be sensitive to the potential presence of hedgehogs and should focus on
increasing suitability by maintaining connectivity between linear features.
- Establishing or replenishing hedgerows around arable fields is recommended to avoid fragmentation resulting from the avoidance of arable land by hedgehogs.