Keeping our finger on the (possum) pulse
A chew card set up to monitor predator activity.
Why bother monitoring predators? Isn’t trapping enough?
Monitoring possum distribution is an important part of City Sanctuary’s work. Monitoring helps us understand where possums are still present so we can focus our efforts and assess how well we’re doing with our predator control work.
Monitoring devices such as motion-activated cameras, chew cards and wax-tags, don’t require much effort from animals to interact with them (cameras require none!). Because they’re simple to interact with, monitoring often reveals a clearer picture of what pests are still around in an area, rather than just relying on catch data to tell us.
Community Ranger Zac recently did a round of predator monitoring in the Botanic Garden. 48 chew cards were deployed in key areas of the garden and left out for a 7-10 day period. Chew cards are baited with non-toxic lure to entice predators to gnaw on them.
After the cards were retracted, each one was analysed to assess bite marks. All this data was then saved onto Trap.NZ to contribute to our big pool of data.
Possum detections in the Botanic Garden- September 2024. Green dots represent possum chews on a chew card.
What did the monitoring show?
As you can see, there are still possums in the Botanic Garden!
It is interesting to cross-reference this recent monitoring data with our trap catch records for the year. We’ve had 13 possum catches in the Botanic Garden this year (thanks to our amazing team of volunteers!)
Notice how there hasn’t been many catches on the north-western side of bush in the garden – right where we got lots of hits on the chew cards!
Possum catches in the Botanic Garden January – September 2024.
Now that we have this intel, what’s next?
In the coming weeks we’ll be adjusting our trap lines in the Botanic Garden. Adjustments usually involve shifting possum traps to new locations and changing trap types. Sometimes moving a trap just a few metres can yield fresh catches!
We put ourselves into ‘possum mode’ and think about why a trap might not be catching and how we can make it more attractive to any resident animals. In some areas we may re-route trap lines entirely so traps can be placed in new locations where there hasn’t been trapping before.
Collections Supervisor, Dylan Norfield commented, "Spring has arrived and blooming is amazing again at the Botanic Garden. No damage has been seen on the magnolias or other prone-to-attack plants. I can’t say enough, the difference it has made to a few years ago."
We’re looking forward to getting possums down to zero in Dunedin’s beautiful Botanic Garden!