In 2016 The Mammal Society Mitigation Guidance Series published the new Water Vole Mitigation Handbook. This publication aims to promote best practice in the surveying and mitigation of water voles by ecological consultants, and to guide and inform decision makers that suitable survey information is provided and suitable mitigation measures proposed (Dean et al., 2016).
The new mitigation guidelines include some key changes to:
· Licensing in relation to the ‘displacement’ of water voles
· Recommended approach to relocating water voles – when to use trapping and when to use displacement
· Appropriate timing for trapping and relocation operations
· Water vole surveys to support planning applications, or other construction activities
Relocating Water Voles
The new guidelines provide some guidance on when it is appropriate to use displacement and when it is appropriate to use trapping. However, they state that evidence is currently lacking on the efficacy of displacement and that research is urgently needed.
Currently displacement is recommended when:
· The maximum working area is 50m on each bank
· Work is conducted between 15 February and 15 April
· Sufficient alternative habitat is available for water voles to move into
Displacement involves the removal of vegetation (by turf stripping or strimming) around the water vole burrow system to make the habitat unsuitable and cause water voles to relocate to nearby unaffected habitats.
There is currently very little published research and anecdotal evidence on the effectiveness of water vole displacement as a technique for relocation. The main issues have been the difficulty in determining success, insufficient sample sizes and differences in study design.
Between 6-11 April 2016, our HCEC Team helped Dr Merryl Gelling, of the WildCru Unit at Oxford University, with a project to compare the effects of different displacement methods on water vole at three sites across Oxfordshire. Ecosulis provided members of staff to help with this project on a voluntary basis. At two of the sites, Standlake and Stanton Hardcourt, they used brushcutters to clear the reed areas from the river. At the third site, Coleshill, the reeds were mainly dug out by excavator. The removal of the reed area from the river and around the water vole burrows will make this area unsuitable and should displace water voles to adjacent suitable areas. This project aims to compare different clearance methods for displacement and to monitor the effects on the water vole populations in the cleared areas.
Water vole Training
On Friday 10 June 2016, eight members of our consulting and contracting teams spent the day undertaking water vole training with Dr Merryl Gelling in Oxfordshire. The day started bright and early with a visit to a site where they are working to check the water vole traps. When we arrived we heard the good news that there were eight water voles in the traps and we were given some background on the project and what we were going to do for the day. Then it was time for the water voles that had been caught to be processed.
We went to each trap location alongside the river and the water voles were removed from the trap, into a bag, where they were scanned for microchips. This was the fourth day of trapping at this site and they were using a mark and recapture method with microchips to mark individuals.
This method is used to estimate population size. Out of the eight individuals, six were already marked. The tag identification number and trap location was recorded for tagged individuals. The two untagged individuals had to be processed. This involved anesthetising the water voles with a gas based anaesthetic and then recording sex, condition and injecting the microchip. The water vole is then placed in a tank to recover, which occurs very rapidly. Once all the water voles were processed, we then looked for field signs of water voles along the river bank.
The rest of the day was spent at the WildCru Unit. We had a very interesting presentation and talk about water vole ecology, field signs and current legislation. We were then given case studies to work through in groups and come up with a plan for mitigation.
The day was really useful for all the team and it was great to get out in the field to see water voles and field signs and to discuss different mitigation options. We would like to thank Merryl for providing the training day for us, and wish her all the best with her research.
Dean, M., Strachan, R., Gow, D. and Andrews, R. (2016). The Water Vole Mitigation Handbook (The Mammal Society Mitigation Guidance Series). Eds Fiona Mathews and Paul Chanin. The Mammal Society, London.