Structural re-design of the Animex Wildlife Bridge for the Hazel Dormouse (Muscardinus avellanarius): lessons learnt from two connectivity mitigation case studies in the UK

Abstract

Abstract The Hazel Dormouse (Muscardinus avellanarius) is an arboreal mammal present in Europe and Asia minor. The population is declining in the United Kingdom (UK), partially due to habitat fragmentation caused by the development of linear infrastructure such as roads, railways and pipelines. In 2016, we designed and tested an arboreal bridge in Britain that was proven to be effective for Hazel Dormice. Subsequently, the bridge materials were upgraded to meet the technical standards of UK road agencies, so that it could be approved and implemented as mitigation on projects throughout the UK. In the UK, each bridge must be certified for technical approval by the relevant road authority and as the bridge is a unique structure, this can pose challenges on projects. The national safety standards of UK roads would not allow common methods used for arboreal bridges across the world to be applied, so we needed specialised engineering and design adaptations to be implemented. Two overarching installation designs were created: the standalone bridge and the retrofit bridge. Several bridges have now been installed across roads in the UK and we will be discussing the development and implementation process from two case studies: i) a 40-metre retrofit bridge to an underpass in St Athan, Wales and, ii) two 76+ metre bridges retrofit to an overbridge and underpass on the M1 motorway in Gayhurst, Buckinghamshire. The St Athan project was quickly approved and easily installed while the M1 project required several alterations to the design and installation methods to meet specific project requirements. This paper discusses what we have learned from these projects, how these projects have influenced the future designs of the Animex wildlife bridge and how this could be applied to future arboreal wildlife connectivity bridges across the world.