The Great Crested Newt (Triturus cristatus) is a European protected species and declining in the UK. This species is being affected primarily by habitat loss and fragmentation. Habitat fragmentation is of particular importance for Great Crested Newts since they typically live in a metapopulation structure and for long-term survival require access to terrestrial and aquatic habitats. Roads that reduce the connectivity between these areas can produce powerful barrier effects for Great Crested Newt migration and dispersal. Understanding and mitigating these potential impacts is particularly important for this species, particularly in the UK where traffic densities and road networks are increasing.

The most promising mitigation is the creation of underpasses or tunnels under roads. These direct amphibians away from the road and aim to provide a link between habitats. However, the effectiveness and success of these tunnels is poorly understood. In addition, factors including placement in relation to breeding and terrestrial habitats, length of tunnel and microclimate within the tunnels is poorly understood.

Over recent years Froglife have developed and deployed an automated monitoring system using high frequency time-lapse infrared image recording. Froglife have undertaken intensive monitoring of eight sites in multiple tunnels both within the UK and Europe. We have recorded amphibian species, sex, age, direction of travel and whether individuals make full tunnel crossings. Initial findings are positive and demonstrate that this species will migrate both ways through tunnels. In addition, we have observed several other amphibian species travelling through tunnels such as Common Toads (Bufo bufo), Common Frogs (Rana temporaria) and Smooth Newts (Lissotriton vulgaris). In many cases we have observed individuals making full crossings through tunnels, demonstrating that they may potentially serve to link habitats. However, the design of the tunnel and surrounding mitigation infrastructure appears to be important in the effectiveness of the tunnels. Using data on amphibian movements at multiple sites, Froglife is working on establishing guidance for the most effective tunnel system for Great Crested Newts and other amphibian species. This will aid in providing valuable conservation measures for Great Crested Newts in an increasingly urbanised and fragmented landscape.

Photo © Dave Kilbey