Trying to find bat roost features in summer is hampered by the foliage in the canopy and understorey.Ground-mapping bat roost features in winter is quick and easy.This woodpecker-hole was first recorded during ground-mapping.When a close-inspection was performed of the woodpecker-hole using an endoscope the internal surfaces were found to be smooth and polished...The culprit - a Natterers bat.

Forestry - Semi-natural

West Heath Quarry, West Harting, Sussex

 AEcol have a long history of cost-effective bat surveys, so when Earthline wanted to take down an area of semi-natural woodland, we were the obvious choice.

Background

 Many consultancies use time-consuming ultrasound survey methods as their one and only bat survey method. At AEcol, we have found that ultrasound methods are more often than not ineffective for tree-roosts surveys. Instead, we find that getting up the tree and looking into Potential Roost Features (PRF) is a far more effective method; it’s quicker and therefore less expensive and provides a far more reliable result. When Earthline wanted to take down an area of broadleaved semi-natural woodland outside Farnham, we were commissioned to perform a climb and inspect bat survey of the woodland.

 Action

 We began by mapping the potential bat-roost trees in the winter months when the foliage was down and we could readily see all the exposed PRF from the ground. We then inspected each feature in turn from the ground to the canopy using powerful fibre-optic endoscopes.

 Our survey team have recorded over 100 tree-roosts holding seven different species bats, and have also performed surveillance on tree-roosts for long-enough to be able to discern, the sometimes subtle, signs that a feature is a tree-roost. As a result, we can predict when a PRF is a roost even when the bats are out. This was the case at Farnham, where although the vast majority of the features held no evidence to suggest bats were present, in one woodpecker-hole the internal surfaces were smooth and polished. As this field-sign is suggestive of the presence of Natterer’s bat and/or brown long-eared bat, and the feature and location of the tree suggested that the feature was suitable, we recommended that this tree should be subject to a higher level of scrutiny in the summer months. Sure enough the tree was found to be occupied by an individual Natterer’s bat, which used the feature intermittently from July through September.

 Outcome

 Following the provision of a compensatory roost site, in the form of a suitable bat-box, the roost tree at Farnham will be legally felled under licence from Natural England during the winter months, when the Natterer’s bat will be in subterranean winter quarters, off-site.

                              If we can help you with a forestry or bat issue, call us now on 01278 429290, or email info@aecol.co.uk