Toxin operations and tracking tricky cliff possums – the Le Bons experience

Written by: Vanessa Mander. Published: 18 October 2022

Over the winter period the Pest Free Banks Peninsula team were out in the hills at Josef Langer reserve. Their task was to install over 60 bait stations filled with Pest Off! (brodifacoum), in a 75 x 75 m grid. The purpose of this operation was to knockdown the possum population in a significant biodiversity area. It also gave our team some vital bush-bashing and bait-laying experience in preparation for our main elimination operation.

Once we started the op, we discovered very quickly that the area seemed to be filled with a lot of very hungry possums. All the bait was gone in every bait station! We refilled them every single week and this continued for the duration of the operation. It was hard to gauge whether these bait stations were encountering significant numbers of possums, or there were just a few extremely dominant and greedy individuals who guarded the sites, eating several times more than the lethal dose of toxin before succumbing. The bait station refilling continued for several months to ensure knockdown in the zone would be significant enough to provide good biodiversity gains.

At the same time as our toxin operation, Manaaki Whenua Landcare Research aimed to study rat behavior, during and post bait station operations to try and improve their understanding of why some individual rats survive population control operations. They helped us refill our stations and put cameras out to monitor the bait-take. Their data will be extremely valuable in considering future rat control efforts in projects all over the country.

Doing this smaller-scale operation in Josef Langer first served multiple purposes. It was an excellent training ground for the staff, who perfected the process of safely and efficiently installing/servicing bait stations. This operation also gave us vital logistical information about how regularly we would need to refill these stations in our main operation. We concluded if we used feratox sparingly, near these bait station sites we could more quickly remove bait-guarding individuals and take the bossy dominant possums out of the picture early, allowing more animals to access bait in a shorter time frame. This way we can maximize the knockdown potential of brodifacoum. More can be found about our tool use HERE.