How to make friends and alienate possums

What we’ve learned so far about urban predator control in Dunedin City.

City Sanctuary was launched in 2020 as the city project for Predator Free Dunedin. For the first two years of the project, we focused on running backyard trapping pilot sites in three suburbs to find out what works and what doesn’t for achieving effective urban predator control.

We are very grateful to the backyard trappers who participated in the pilot suburbs of Māori Hill, North Dunedin and Caversham. It required a lot of time and effort to undertake the surveys and chew card monitoring rounds – thank you to everyone who was involved!

This kind of backyard trapping trial had never been done so we are proud to be trailblazers informed by the Dunedin communities who were involved. What we learned from these trial sites has been very valuable for helping us chart a course for leading predator control in Dunedin city going forward. It’s also given us a robust set of recommendations to pass onto other urban predator control projects around New Zealand.

Our full report will be published next year. In the meantime, we’ve summarised the top ten learnings and recommendations which are most relevant to our new operating model. If you’re interested in finding out more, please get in touch.

1) Grids are gone

During the pilot sites trials, we aimed to have 1 in 10 households involved in trapping. A trap network or grid model is commonly used in rural environments to ensure there is optimal trap coverage of the landscape and relates to the home ranges of target species. However, when applied in our urban Dunedin setting, we found that the 1 in 10 household grid model resulted in traps being rolled out across properties with little or no rodent or possum habitat. Residents in these properties often had low or no trapping success and became disengaged with their traps. In contrast, residents who lived on properties with habitat favoured by predator species were more involved in the project and had greater trapping success.

With our project changing to a focus on possums, it is clear that there is little value trapping on properties where there isn’t any optimal predator habitat. By using an approach that is more targeted to habitat, we can save time and resources. Possum habitat has been mapped across the city, with a focus on areas that form corridors and pathways for possums to travel through. In addition, our trapping areas are based on the closeness to the operating areas of the other two Predator Free Dunedin projects - The Halo Project and the Otago Peninsula Biodiversity Group - to decrease the likelihood of possum reinvasion. It goes without saying that possum habitat is also habitat for native birds, lizards and insects, so focusing on these areas will help protect our native species in the right places.

2) Use the right trap in the right place

Many pilot site trappers who didn’t get help installing their traps ended up being less involved in trapping long-term and less likely to set their traps. This was particularly evident with complicated traps, such as the Goodnature A24. People who did manage to set their A24 traps reported feeling less confident than those who used Victor snap traps.

Trappers also became disengaged with their traps when they failed to catch anything which affected the overall project. Survey responses and personal feedback showed us that it is important to match the trap type to the right environment and the user’s confidence. We’ve developed a trap type matrix which we use as a recommendation guide for working in the four common environment across Dunedin city: urban backyards, semi-rural properties, open spaces and forested reserves.

3) Staff help backyard trappers install traps

To decrease the amount of time staff spent distributing traps, we tested giving out traps at public events and using a drop-off system. Although detailed information was provided about how to install and manage the traps, it was soon evident that many backyard trappers didn’t install their trap or hadn’t installed their trap correctly. This was particularly the case with more complicated traps such as the Trapinator and A24. Common feedback was to have staff help install the trap and demonstrate how it works. 

As City Sanctuary hones in on possums, staff or trained volunteers now install all possum traps to ensure the traps work effectively, are set in a good location and the residents feel confident using the trap.

4) Staff need to manage some backyard traps

From the pilot sites, we found that even though some backyard trappers were willing and enthusiastic at the onset of their trapping experience, trap check frequencies and data reporting waned significantly over time. This was either due to lack of time, low trapper confidence or not catching anything. In other situations, people were keen to be involved but were not able to check traps themselves.

To ensure project milestones of low possum numbers are met, staff are now helping check and manage some backyard traps in important locations when residents are not able to do this themselves.

5) Use public engagement methods that achieve goals

Although very important, we found that wide-casting public engagement methods such as community sessions and stalls at public events were time-consuming and didn’t result in high numbers of traps being installed.

For example, students in the North Dunedin pilot site were initially engaged with at two Orientation Week events. At the 2021 event, 74 students signed up to host a trap but over the following months led to no successful trap installations. Instead, the most successful methods of trap deployment in this site was a targeted 3-hour door-knocking spree (29 properties) and door knocking at student flats that had expressed an interest to host a trap during the 2021 Orientation Week event (48 properties).

In other suburbs, targeted letterbox drops and phone calling to properties containing habitat are engagement methods that have efficiently recruited good numbers of new backyard trappers in priority areas.

6) Volunteers shouldn’t be relied on to complete core project work

Although our pilot site trappers expressed interest in volunteering, less than 5% of registrants actually gave their time to help with core operational work. This may have been due to the lack of ‘appealing’ volunteer opportunities such as bird monitoring or trap line checks that hadn’t been set up at the start of the project.

Lack of volunteer participation meant staff had to do many core operations that had been assumed could be completed by volunteers, such as recruiting and supporting new trappers, and distributing and managing traps. This led to increased pressure on staff to get key tasks completed within the project time frame.

We are incredibly grateful for everyone who gives their time volunteering for the City Sanctuary project. Going forward, we will continue to offer volunteer activities that are complementary to core project work while staff remain responsible for completing key operational goals.

7) Be open from the start about what’s involved with trapping

Backyard trappers who participated in the pilot sites gave feedback during the trial to share their views and experiences. Survey results showed that common concerns about trapping included: safety of the traps for kids and pets, handling dead animals, animal welfare, and concerns about a lack of personal experience in predator control. These concerns were similarly ranked in the Predator Free Dunedin Residents Survey, the Dunedin City Council Survey and the Manaaki Whenua Attitudes Towards Predator Control Survey.

With all our advertising and communications material, we aim to present trapping information clearly and honestly. Residents who are still not comfortable doing trapping themselves but who live in a priority area receive support from staff to manage traps on their property.

8) Support backyard trappers regularly

Survey results also strongly indicated that backyard trappers valued regular personal check-ins and support with City Sanctuary staff. These visits also resulted in better involvement with the project, higher catch rates and improved data.

From this learning, we now check-in with our backyard trappers every three months to see how their trapping is going and provide support.

9) Provide traps free to backyard trappers

Another survey question we asked was whether backyard trappers would be willing to contribute financially toward the cost of traps. This question was also asked in two other surveys. 62% of participants in the People’s Panel survey were willing to pay for a trap at an average cost of $50, while 80% of respondents in a Predator Free Dunedin survey were willing to contribute an average of $61 toward a trap.

In the City Sanctuary survey, 49% of backyard trappers in Māori Hill were wiling to buy a trap with 31% happy to spend up to $50 and 29% over $100. At the end of the pilot site survey, the Māori Hill residents were asked again if they would be willing to donate toward traps. After their experience with the traps and the project, all of the survey respondents were happy to donate with an average price of $26.10 for a trap.

Participants who indicated they wouldn’t contribute financially toward traps most said this was due to restricted funds. To ensure that properties in key locations all receive traps, we don’t want to have any barriers to people getting involved. We’ve made the decision not to require a financial contribution from residents when we install traps.

Instead, people have the option of making a donation through the Predator Free Dunedin Give A Little page.

10) Community based, organisation led

City Sanctuary’s original plan aspired to be a community-led project. This is a common model or reference within the wider Predator Free New Zealand movement, describing a project where residents and community groups are expected to kickstart, lead and manage predator control operations in their community.

Based on what we learned from the three pilot sites, residents and community groups were supportive but time poor, unskilled in trapping and unable to undertake predator control to a standard needed to meet operational targets.

Instead of expecting the community to lead the project, we pride ourselves on being a community-based project: inspiring, educating and supporting communities to get involved in trapping to see meaningful outcomes for native species.