Monitoring & evaluation
Being at the forefront of mainland eco-restoration means trial and error are a key feature of the Trust’s work. Monitoring and evaluation work are daily activities.
Developing and monitoring the fence
The fence is probably the single most important feature of Zealandia. Prior to construction, extensive trials were undertaken with wild animals to develop a design that would exclude burrowing and climbing animals, and withstand the environmental conditions prevailing in the Wellington area. It was also designed to exclude animals as small as mice and as large as cattle. Monitoring of the fence is a regular occurrence to check for failures and undertake maintenance. After construction, issues were noted with construction because there were failures in the ‘top hat’ due to expansion and contraction, and ongoing breaches by mice.
- Trial modifications to materials used to fix the top hat to the mesh were undertaken in the field and a design modification confirmed that has virtually eliminated expansion/contraction
- Trials with captive wild-caught mice confirmed they could climb over the ‘top-hat’ in certain situations – extensive trials were undertaken and a modification to the top hat was installed that prevents mice gaining access to it.
- Trials with mice confirmed that small mice could squeeze through gaps in the mesh that had expanded only 1mm and could climb vertical metal sheets if they were able to gain footholds between lapped joints or at attachment points – subsequent trials with different mesh designs have confirmed a mesh is available that will withstand impact and not distort sufficiently to allow mice through it. A fence was designed that combined the new mesh topped by an appropriately attached vertical metal sheet to prevent mice, weasel and tuatara climbing over. This alternative fence was constructed in 2005 around c 1ha within the valley.
Auditing for mammal re-invasion
Regular audits for mammalian re-invasion are undertaken using tracking tunnels, traps and detector dogs to increase detection probability at the earliest possible time and success of any control programme.
- The audit tunnels were designed to double as trap covers in the event of a detection and have proved successful in both roles.
- Our mouse population has been regularly monitored since 2003 (every two months using three-four traplines in different habitats) to record any changes in abundance and breeding status, especially relative to the annual control programme.
- A multi-species detector dog was trialled for a couple of years. However, with a lack of live prey for ongoing training and rewards, it proved inadequate for ongoing monitoring (it was unable to be trained on live targets and trails outside the sanctuary valley where there were multiple species and too many potential targets).
Auditing for pest plant re-invasion
- Weed surveys are undertaken every year to map extent of target species and effectiveness of control. Surveys are usually undertaken by grid searching areas to locate and remove priority species, but other methods are used as appropriate eg photography to map the location of flowering exotic trees. Several student projects have been undertaken focussed on weeds such as weed establishment after pine tree removal and recruitment of Berberis.
- Vegetation plots and survey transects were established before construction of the fence in order to monitor changes in vegetation over time. Photopoints have also been established to assist with monitoring change. Several student projects have been undertaken looking at aspects of the native vegetation.