Moorhouse et al (2014) hedgehog hedge agri-environment

Title: Hugging the hedges: Might agri-environment manipulations affect landscape permeability for hedgehogs? Biological Conservation. 2014

Authors: T. P. Moorhouse, S.C.F. Palmer, J.M.J. Travis & D.W. Macdonald

Country: Lowland England

Background to study

A simulation study of hedgehog movement in response to altering the extent of hedgerows, field margins and pasture across the landscape to test whether the distance moved by hedgehogs increases with increasing cover of preferred habitat types. 

Method

• Individual dispersal movements by hedgehogs were modelled using a Stochastic Movement Simulator (SMS) within which the extent of hedgerows, pasture and field margins were manipulated to represent losses and additions of these features in a 11.2 x 8.47km lowland agricultural area of south Oxfordshire.
• Hedgerows were modelled as the % of field boundaries that were hedged and were modelled by creating a 2.5 m buffer at field edges and manipulated to include 25, 50 and 75% of fields.
• Field margins were modelled as the % of hedged field boundaries that had an additional conservation field margin and were modelled by creating an additional 6 m wide buffer at hedged field boundaries and manipulated to include 0, 25 and 50% of hedged fields.
• Pasture fields extent was set at 13 and 25% for each of the hedgerow and field margin models.
• Hedgehog movements were modelled assuming movements were based on a perceptual range of 5 and 10, 2m grid cells and each individual started from a random location, finished moving after 5000 steps (where step is the movement between neighbouring 2x2m cells) and distance moved (500, 1000, 1500 and 2000 m from the starting locations) was calculated within each modelled landscape.
• The proportion of modelled hedgehogs that moved further than each distance threshold was evaluated against each of the modelled landscapes to determine how and which landscape metrics influenced hedgehog dispersal. Models were additionally evaluated by manipulating the cost of movement by field use type (pasture and other grassland) and by the presence of badgers.

Key results

• Increasing the proportion of fields with hedgerows from 25% to 50% resulted in an increase in the distance moved by the modelled hedgehogs and included a 13% increase in modelled hedgehogs making movements of 500 m, 25% making movements of 1000 m and an additional 35 and 51% of modelled hedgehogs making movements of 1500 and 2000 m respectively.
• There was no evidence that increasing the proportion of fields with hedgerows to above 50% consistently increased the distance moved by hedgehogs.
• Varying the cost of movement through grass and pasture and by introducing the presence of badgers did not substantially affect the relationship between the distance moved by modelled hedgehogs and the modelled landscape metrics.  
• Increasing the % of hedged fields with conservation field margins did not substantially increase the distance moved by modelled hedgehogs.
• Increasing the % of pasture or other grassland fields in the landscape led to a small (1%) increase in the % of modelled hedgehogs that moved 500 and 1000 m but decreased the % of individuals that moved 1500 and 2000 m suggesting this landscape metric is unlikely to be an important factor in hedgehog dispersal.

Key messages to landowners and managers derived from these results

• Reinstating and repairing hedgerows within agricultural dominated landscapes may help to increase the dispersion of hedgehogs where populations are currently fragmented and is recommended where suitable hedgehog habitat is currently disconnected.
• Creating additional grassy margins along hedgerows and pastureland within the landscape may increase suitability of rural landscapes for hedgehogs.