Haigh et al (2012) Intra and interhabitat differences in hedgehog distribution and potential prey availability
Title: Intra- and interhabitat differences in hedgehog distribution and potential prey availability, Mammalia 76; 261-268. 2012
Authors: A.J. Haigh, F. Butler & R. M. O’Riordan
Background to study
A study investigating the distribution of hedgehogs in mixed agricultural landscape and whether this is influenced by the location and abundance of invertebrate prey.
- Between June and November 2009, hedgehogs were locating using spot light surveys, marked with uniquely coloured heat shrink tubes, injected with a Passive Integrated Transponder (PIT tag) and radio tagged within a mixed agricultural area dominated by horse grazed pasture, arable fields with margins, and hedgerows. Other mammal encounters or signs were also recorded during study period.
- Hedgehogs fitted with radio transmitters were tracked for a total of 893 hours over 160 nights.
- Potential hedgehog prey were sampled weekly in areas where hedgehogs were active and included:
- Counts of surface invertebrates along 60 m x 0.46 m in arable fields covering areas of low and high intensity use by hedgehogs and included 71 and 72 transects surveyed in October 2008 and March-November 2009 respectively.
- Counts of surface invertebrates in pasture fields between March and November 2009 within three 0.25 m2 quadrats placed at random locations along 54, 60 m long transects.
- Counts of surface invertebrates within three randomly placed 0.25 m2 quadrats within 60 m long transects located at the edge and centre of pasture land (six transects in each) and the edge and centre of arable land (two transects in each). Surveys were conducted in October 2008.
- The occurrence of hedgehogs in relation to prey and the proportional use of habitat type and edge were investigated from the data obtained.
- Hedgehog activity increased in arable land during September until hibernation, which concurred with an increase in surface invertebrates during this time.
- There was a significantly higher abundance of invertebrate prey and density of molluscs (2.6/m2) compared with earthworms (0.3/m2) in the arable land during October 2008 than 2009, whilst in 2009, a significantly higher density of earthworms (0.6/m2), compared with molluscs (0.3/m2) were observed.
- Earthworm density increased from 0.42/m2 in July to 0.95/m2 in August 2009.
- There was a significantly higher density of surface invertebrates in areas where hedgehog activity was highest (3.48 invertebrates/m2) compared with low intensity foraging areas (0.97 invertebrates/m2).
- Hedgehog activity coincided with surface invertebrate activity, with significantly more activity being observed in areas of high prey density within arable land.
- Hedgehogs spent significantly more time in the centre of field than along the edge in horse grazed pasture land bounded by bramble dominated hedgerows and in arable land, however in pasture bounded by Hawthorn trees and no understorey, hedgehogs spent significantly more time along the hedgerow than in the centre of the field.
- Surface invertebrate density was greater under the hedgerow than in the centre in all areas which coincided with hedgehog activity in pasture bounded by Hawthorn trees only.
- The relative abundance of surface invertebrates was significantly variable between arable fields and between the pasture fields.
- Rabbits, foxes and badgers were observed to utilise the study area.
Key messages to landowners and managers derived from these results
- Hedgehog distribution is likely to be driven by the density of surface invertebrates, thus management of agricultural land that enhances invertebrate fauna is recommended and includes:
- Maintaining and/or reinstating hedgerows with good understorey
- Creating beetle banks and grassy field margins and using mixed stock for grazing
- In light of development, mitigation habitat creation or enhancement should include a variety of habitat types to allow for seasonal variation in prey and subsequent foraging activity of hedgehogs.