McIvor 1997 Predicting occurrence of the hazel dormouse using a habitat suitability index model in Andrew’s Wood and Lady’s Wood, Devon. MSc dissertation, University of Bournemouth

Authors: C M McIvor

Country: England

Background to Study:

The dormouse is recognised as one of the most elusive mammals in England due to its nocturnal and arboreal habits.  This poses difficulties in determining species occurrence so that they can be effectively managed and conserved.  Advances in computer modelling have shown Habitat Suitability Indices (HSI) to be valuable in predicting spatial distribution of species and isolating suitable habitat and as such may be useful in facilitating design of management plans and mitigation strategies.

Method:

• Two woods currently monitored for dormice using nestboxes were used to obtain Habitat Suitability Indices based on vegetation composition of different management compartments. HSI’s were compared with nest box occupancy and gnawed hazel nut presence to assess its effectiveness for predicting dormouse presence.
• A Habitat Suitability Index was derived from habitat variables important to dormice including canopy cover, structure and connectivity, and number of soft and hard mast producing trees. Each variable was assigned a Suitability Index which ranged from 0 = unsuitable habitat to 1 = suitable habitat and mean of all variables (equally weighted) were calculated to give a total habitat suitability index for different compartments within both woodland sites.
• Distance from footpath and hedgerows were calculated to investigate their effect on nest box occupancy.

Key Results:

• There was little difference in the Suitability Index scores for the woodland compartments containing nest boxes (0.3379 – 0.482) and nest boxes were occupied throughout most compartments at both sites but occupancy in some did vary annually.
• There were no significant correlations between nest box occupancy and the Habitat Suitability value assigned to different woodland compartments indicating that the variable included in the Index were not good predictors of dormouse presence in the study sites.
• When suitability variables were analysed independently, the percentage lower canopy cover was found to be useful in predicting dormouse nest box occupancy.
• The number of canopy trees and number of plant species were not associated with nest box occupancy nor was distance from footpath or hedgerow.

Key messages to landowners and managers derived from these results:

• Habitat Suitability Indices present a potential method for predicting dormouse presence; however more work is needed to assess the relative importance of habitat variables in different habitat types.
• Nest boxes are valuable for monitoring dormice and may increase dormouse activity in woodland compartments that may appear sub-optimal.
• Dormouse activity may fluctuate annually in different woodland compartments and surveys to establish presence need to be conducted prior to any woodland operations being carried out.

Key words/phrases

Dormice; Muscardinus avellanarius; Habitat Suitability Index; nest box; predicting spatial distribution