Phase Two Predator Control for Oruawharo Bay

RAOUL STUART (Chair of Oruawharo Medlands Ecovision committee)

Aotea/Great Barrier Island is home to a number of taonga bird species that need protection from introduced predators. In the Oruawharo Medlands area these include pāteke/brown teal, mātātā/fernbird, matuku hūrepo/Australasian bittern and moho pererū/banded rail. In addition, there are numerous other bird species, lizards and freshwater fish species whose habitat is in need of improvement or restoration. 

Oruawharo Medlands Ecovision (OME) is a local volunteer community group formed in late 2018 to restore and protect the ecology and biodiversity of the Oruawharo Bay area of Aotea/Great Barrier Island (www.omeaotea.co.nz - for their new web page). In 2019 they received funding from the Aotea Local Board to commence a Phase 1 project to trap predators in the Medlands beach area and to begin a replanting programme as outlined in their project plan and feasibility assessment(1). 

The key objectives were to: 

• Reduce rat numbers 

• Increase bird numbers 

• Seek visible community engagement. 

Following the initial feasibility study, OME was successful in securing three-year funding from the DoC Community Conservation Fund to restore the Medlands Wildlife Management Reserve, which consists of the wetland between the main road (Medland Road) and the houses of Sandhills Road to the north as well as the riparian, DoC managed strip along Oruawharo Creek, to the south. 

This resulted in the project area covering the catchments of both streams that flow into Oruawharo Bay. Since award of those grants, OME has been busy trapping rats, mice and feral cats, monitoring and controlling introduced pest plant species in the wetland, replanting as well as undertaking quarterly Waicare monitoring of the water quality in both creeks. The ongoing Phase One project involves extensive trapping throughout the dunes, reserves and wetlands of Oruawharo Bay, employing snap traps in protective wooden boxes to catch rodents, and larger wire traps to live-catch feral cats. 

Since initiating the project there has been very good community engagement. A regular group of volunteers turns up for a weekly working bee in the wetland and there has been good uptake of rodent traps from the Aotea Trap Library by residents on private properties around Medlands. When the first survey was carried out in 2019, 31 properties were recorded as carrying out pest control but now, in 2022, 80 properties are involved. But the downside of private trapping is traps are only checked when people are in residence. 

However, use of tracking tunnels to assess the presence of rodents has revealed that localised household trapping has not had sufficient impact on local rodent populations to provide good protection for the local bird life(2). Results showed that although over 4,000 rodents have been caught since trapping started there were still relatively high rodent densities. The study also highlighted that mice are a bigger problem than was initially considered, especially in the Muehlenbeckia covered dune systems. The overall conclusion was that rodent numbers followed seasonal trends rather than any obvious decline from regular trapping. One likely cause for the low impact is the current pest management area is confined to a long and narrow area that has a large boundary for re-invasion from outside. 

OME are therefore proposing that the current trapping area be extended to try to reduce reinvasion into the current Phase 1 area with the prospect of greater biodiversity gains, including more birds, insects and reptiles, and better seedling survival in the regenerating bush. By joining up to the Windy Hill Sanctuary to the south of Oruawharo, where positive biodiversity gains have been demonstrated, extending up to the western ridgeline and to the northern end of the beach towards Sugarloaf, we aim to create a bigger corridor of safer breeding sites and broader dispersal areas for fledged birds. 

In line with those goals OME submitted a grant proposal this year to fund a feasibility study for Phase 2. This application was successful in receiving funding of $26,880 in August 2022 from the Auckland Council’s Community Coordination and Facilitation grant. This has meant we can begin a community engagement and project planning phase, looking to expand our pest management project to include private properties as well as more DoC and Auckland Council managed land in the valleys, growing the project area to cover an area of approximately 1,750ha. There are 235 separate titles in the project area of which 63 are over a hectare and will be the initial focus for Phase 2. The project will be overseen by a Phase 2 Working Group with specialist knowledge input from a group of Advisors. 

Community engagement will occur in a step-by-step manner, that will gauge people’s interest in being involved, through a face-to-face conversation based on a short questionnaire supported by an outline of the plan and how it might proceed. Once this work has been completed we expect to have a clearer picture of how many properties will be included and where there might be any large gaps in pest management. 

Using only snap traps in an area the size OME is proposing is neither cost effective nor feasible, as had been shown in the past from trials by Windy Hill Sanctuary. We will therefore need to deploy bait stations containing first generation toxins such as diphacinone, in accordance with the best practice standards as is currently done in Windy Hill(3). However, preferences of private landowners will have to be taken into account in our choice of tools that will be deployed. Another important issue will be access to private land. Some property owners might prefer to undertake their own pest management, which would be acceptable as long as trapping data is collected so that there are records for the whole of the Phase 2 area. 

Given the tools for pest control are constantly evolving we will work closely with Windy Hill Sanctuary and with the Tū Mai Taonga project(4) to trial or deploy new pest control methodologies. One exciting development is the AT220 self-resetting trap from NZ Autotraps that can be used at landscape scale(5). These could prove to be a good option for bach owners who might wish to be involved in the project but prefer not to use toxins. 

To enhance our engagement with the community we will soon be setting up a community hub (OME Eco-Pod) in Medlands near the community garden. Funding for the hub building has been secured from the Aotea Great Barrier local board and will soon be installed. This will give OME a physical presence the area to store tools and equipment, and be a one-stop-shop for the community to visit and hear first-hand about current restoration projects, why they are being carried out and how they might be involved. 

The desired outcomes for OME Phase 2 are the same as those determined from the outset of OME’s first feasibility report for Phase 1, i.e., reduced rat numbers, increased bird numbers and visible community engagement, at the top of the list. The difference with the current Phase 2 project is one of scale and increased participation of landowners and other conservation groups, moving the project from working only on public land to also include private property. In November 2022 we started baseline rat monitoring and will continue to monitor quarterly in synchrony with the other sanctuaries and projects on Aotea. We hope to show that the anticipated reduction in rodent densities over time will be the direct result of the work being carried out. 

We see OME Phase 2 as a collaboration with Tū Mai Taonga who have major funding from PF2050 and DoC Jobs for Nature to eradicate feral cats and significantly reduce rats in the northern blocks of land that comprise Te Paparahi with a long-term plan to eventually roll their programme further south. It will be several years before they reach Oruawharo Bay and beyond. By starting the landowner engagement phase and baseline monitoring now, followed by pilot trials and more extensive predator control in the Oruawharo Bay area, we hope to have laid a lot of the ground work to seamlessly merge with Tū Mai Taonga as it extends to the southern end of the island. 

Conclusion 

The Phase 2 project proposal is born out of a desire to help Aotea become predator free sooner rather than later. We see this as possible through collaboration between all organisations and individuals involved, Tū Mai Taonga, Iwi, DoC, Auckland Council, sanctuaries, community groups and the wider community. Having this very visible pest control project operating in a residential area and along walking tracks is a window into the conservation process and will help promote the benefits of intensive pest management as a pathway to eventual eradication. 

Acknowledgements 

Many thanks to Lotte McIntyre for her feedback on this article, provision of images and leadership on the ground in coordinating many of the OME activities. We would also like to thank Lynda Moran and Hannah Smith from AGBET for administrative and financial advice and support. Funding for this project has come from grants from the Aotea Local Board, Auckland Council and Department of Conservation. 

References:

1. Oruawharo Medlands Ecovision (2019). Community-led biodiversity protection and restoration at Oruawharo Medlands: Project plan and feasibility assessment. Editor: Gorter Rendt. July 2019. 

2. Ogden J (2022). Phase 1 progress report. Oruawharo Medlands Ecovision. October 2019 – October 2022. 

3. Ritchie J (2019). Vertebrae pesticides - toxin breakdown sheet. 

4. Tū Mai Taonga: https://www.tumaitaonga.nz 

5. Bay Bush Action AT220 Field Trial (2021). A review of the NZ Autotraps AT220 for controlling rats and pos-sums in areas over 250 hectares. http://www.baybushaction.org.nz