Totterdown Farm Barns: Bat Mitigation


BSG Ecology was commissioned to survey a series of derelict farm buildings, known as Totterdown Farm Barns, for signs of bat activity. One of the barns was in a derelict state when we visited it, with an unlined roof and numerous roosting opportunities. Our surveys identified a maternity roost of Natterer’s bat, and use of the barn and surrounding land by common and soprano pipistrelle bats. The proposed development would have resulted in damage to the bat roost.

BSG Ecology’s role in the project

In order to enable conversion of the buildings to residential dwellings to proceed, we negotiated with the LPA and NE to agree an appropriate mitigation strategy that was considered by all parties to have a high likelihood of success. To achieve this, BSG Ecology worked closely with the client’s architect to design a bespoke conversion. Following planning permission, we secured a European Protected Species (EPS) licence and supervised the implementation of all works.


The barn was successfully converted and work was timed to avoid the seasonal presence of the important Natterer’s bat maternity roost. Our role on site meant that twenty other bats were located and moved to safety during construction.

The barn was modified to create a dedicated bat loft in the location of the existing roost.

Access for bats was retained through the original open barn door entrance at the south side of the barn. Roosting areas including a gap in the stonework at the western gable apex and between ridge beam and ridge tiles at the western end were retained. The existing timbers of the ridge beam and rafters were retained.


BSG Ecology has completed a three year monitoring programme as a requirement of the Natural England licence, and through our liaison with the Cotswold Water Park Society our monitoring continued for an extended period. The site is now routinely monitored by local volunteers.

Our monitoring confirmed that the Natterer’s colony continues to successfully breed within the barn co-existing with the new residents.

Key points

The site continues to support the maternity colony, and the success of mitigation can be attributed to:

  • Retention of existing roosting location and careful siting of access points and flight lines.
  • Temperature – because of its design the conversion has increased the roost temperature and made the temperature more stable.
  • Timing of conversion during the autumn period, with work stopping during the following maternity period to allow bats to investigate and recolonize the roost.

Winner of the Bat Conservation Trust Roost Award for Mitigation 2012

Key Services

Residential/ Commercial Development