Introduction
- Project description
- Planning permission for a new mixed use development required the building of two Lesser Horseshoe Bat (LHB) night roosts. The purpose of the night roosts were to extend feeding ranges and provide additional bat colony resilience by providing additional occasional shelter/feeding perches.
- Ecologist’s name and contact details
- Alastair Chapman; alastair.chapman@fdean.gov.uk
- Client’s name
- Forest of Dean District Council
- Site postcode
- Cinderford - GL14
- Planning authority
- Forest of Dean District Council
- Brief site description
- There is an established Lesser Horseshoe Bat (LHB’s) maternity roost in the area and the mixed use development required a detailed mitigation and enhancement approach for the LHB’s and other species. As part of the enhancement & mitigation package two new LHB night roosts were to be constructed in adjacent woodland.
Radio tracking data from an existing main roost site, habitat suitability assessments together with future Forestry Plans were used to select locations which were considered likely to be the most useful to the bats and reduced chance of substantial disturbance.
Pre-works roost structure
- Type of structure
- Other
- Use
- Other
- Condition
- Not In Use
- Main construction material of walls
- Block
- Roof design
- Flat Roof
- Roof material
- Not Applicable
- Internal roof structure
- Not Applicable
- Lighting present on site and its proximity to the roost
- None
- Photos or annotated figures of roost structure
Pre-works roost description
- Species
- Lesser horseshoe bat
- Roost material(s)
-
Proposed works
- Description of works
- In addition to the ecological requirements we were keen that that the structures should be as simple as possible, easily replicable and minimise on site construction time by prefabrication.
Our final design was based on precast concrete sewer rings, with an internal baffle and upper chamber. An idea being that these could be prefabricated off site and transported and easily assembled on site.
- Relevant annotated figures
Monitoring data
- Length of monitoring proposed
- Static bat recorders (loggers) were placed inside the night roosts for 17 consecutive nights in July 2018. Of the 6700 sound files recorded in the period half were identified as bat passes. Whilst the recorders will have undoubtedly recorded bat passes nearby, but outside of the roost, the level of recording clearly indicates the structures were being regularly used.
- Frequency of monitoring
- Two visual inspections have been made in 2020 with a count of 3 bats using the structure.
Final details
- Lessons learned
- Water tightness
We soon found that the manhole cover on the top (for future access) was not water tight and needed sealing. In hindsight some form of fabricated hatch cover may well be better.
Prefabrication
The contractor chose not to do any internal fabrication off site which led to a longer on site construction time as they wanted to avoid damage in transit. It remains an option for future projects.
Appearance
Landscaping with native climbing and thorned plants has been undertaken and does require some annual maintenance and securing to the structure. Vertical timber cladding was considered as a measure to ‘soften’ the impact of the structure, but not considered necessary for these locations.
Internal features for other species
The focus for the roosts was for Lesser Horseshoe Bats, however a greater range of features could have been added for crevice favouring bat species.
Costs
There was a certain amount of developmental and risk cost within the overall budget (£13.5k for two); as a result of trying something new. Overall it is considered costs could potentially be reduced dependant on access and practical experience.
