In 2015 BSG Ecology was commissioned by O&H Hampton Ltd to carry out ecological monitoring of great crested newt use of tunnels. The aim was to determine the success of mitigation relating to the recently-constructed Western Peripheral Road, Peterborough. The road bisects Orton Pit Special Area of Conservation (SAC), which was designated for its hard oligo-mesotrophic waters and for supporting the largest known population of great crested newts in the United Kingdom.
Although the road cuts through arable habitats of low value to newts, measures were designed into the proposals to ensure that impacts including fragmentation of the great crested newt population did not occur as a result of the road. These measures included the creation of three new ponds, two new sections of ditch, and areas of species-rich grassland. These habitats were created with the primary aim of providing breeding and terrestrial habitat for great crested newt, but also to support other protected species including water vole, reptiles, grass snake and common lizard and stoneworts.
The scheme design aimed to prevent fragmentation of newt habitat, and included the construction of terrestrial and aquatic tunnels beneath the road to retain connectivity for newts. The conditions of the planning consent and Natural England development licence stipulated that monitoring of the tunnels was required to determine if they were successfully used by great crested newts.
Approach to Monitoring
The tunnel monitoring protocol for great crested newts used on earlier stages of the road was to use drift fencing and pitfall traps to determine the use of terrestrial tunnels, and bottle traps for monitoring aquatic tunnels. These measures are considered to be intrusive, however, and given the importance of the population other methods were considered.
An alternative method involving the deployment of camera traps and infra-red lights mounted on the ceiling in the centre of each tunnel was trialled. It is less labour intensive and can be undertaken continuously throughout the active period for newts. This also meant that periods of weather in which newts are most likely to disperse could be effectively sampled.
BSG advised on the installation of the camera system undertaken by O&H in mid-May 2015, since which time it has run continuously. Each camera is connected to the mains and a computer. Continuous logging of data occurs whenever movement is detected within a tunnel. During the 2015 autumn migration period a total of 12 great crested newts were recorded passing through the tunnels. During previous baseline data collection in autumn 2005 and 2006, an average of 14.5 great crested newts was recorded crossing the site. These initial results are considered to be very encouraging, as they point to the success of the tunnels.
The continuous monitoring of the passage of newts and other wildlife through the tunnels has identified improvements in survey method and tunnel design / specification. Firstly, to aid identification of newts a temporary ‘bank’ has been constructed in the centre of the aquatic tunnels. The bank requires newts to leave the water, and ensures they are visible and therefore identifiable to species level and age class. Other improvements have been made to the aquatic tunnels to stabilise flow conditions and reduce turbulence. In the terrestrial tunnels improvements have been identified that will provide dispersing newts with more cover from predators (rats and grass snake have been recorded using the tunnels).
Other species recorded using the tunnels include smooth newt, water shrew, wood mouse, common shrew, grass snake, mallard, red-legged partridge, red fox, common toad, bats and fish. This list of species reflects the success of the habitat creation work undertaken by O&H Hampton within the site and surrounding area. Most of these species would not have been recorded using the tunnels if conventional monitoring methods were used, and may have been deterred by the presence of drift fencing and the regular disturbance by personnel.
The first year of monitoring of tunnels under the Western Peripheral Road has been successful: all four tunnels have been continuously monitored, and the footage captured has demonstrated that the mitigation measures are effective. The tunnels are being used by similar numbers of great crested newts as were recorded prior to construction, and a range of other species. Further monitoring and refinement of the method over the remainder of the monitoring period will allow the effectiveness of the mitigation to be confidently determined.
Over the five year monitoring period (2015-2020), the novel approach taken to monitoring work will result in a cost saving for O&H Hampton in comparison with more established methods. This is due to both reduced material and personnel costs and time saved organising programmes of monitoring visits.