THE CHEW CARD VOLUNTEER SURVEY RESULTS ARE IN...
On Thursday, the preliminary results of our Volunteer Chew Card Monitoring Survey were shared by Dr Craig Bishop at our 'Share the Results' evening for volunteers and citizen scientists at Birkdale Hall.
In late July we called for volunteers to join our Chew Card Monitoring Survey organised by Pest Free Kaipatiki and RIMU (Auckland Council's Research and Evaluation Unit). We got a whopping response (more volunteers than we needed!) and enlisted 50 volunteers to put out chew cards on lines set up by RIMU in 28 Kaipātiki reserves.
Volunteers set out cards on lines in reserves set up by RIMU and collected them three days later to be analysed by the RIMU team.
A big thankyou to everyone who participated in this project. We look forward to finding tasks for all of you in the next phase of our predator programme.
KAIPATIKI CHEW CARD MONITORING RESULTS
From the cards analysed, 39% had rat bites or marks and 7% had possum ‘browsing’.
Mice also scored high at 35%, 2% other (includes mustelids, hedgehogs). Two cats and one dog provided proof that peanut butter is definitely a favourite among all species!
Craig Bishop's Summary:
Rats appear to associate strongly with waterways; a much higher proportion of cards were usually chewed on lines that ran close to waterways.
Many small bush reserves that are surrounded by dense urban areas had lower indications of rats. We are still unclear exactly what is causing this. In the case of the more urbanised eastern-most part of Kaipātiki Local Board, perhaps this could be due to contracted industrial predator control? In the case of the smaller reserves, at this time of year rats may still be lurking in and around houses and backyards? Or perhaps rats are less abundant in urban house landscapes compared to urban forest patches? This warrants further investigation.
In several cases, chew cards in close proximity to long standing trapping lines or bait stations showed fewer chew marks. Tuff Crater in particular had no rat chews on the 50 chew-cards that were deployed around the crater margin.
In general, lines within the larger bush reserves had a higher % of cards chewed by rats. It seems that there is enough habitat and food in these areas to sustain higher populations even at this time of year.
While a few reserves (in particular Castleton Reid, Chelsea Heritage Estate and the Golf Course) had possum chew marks all along the card lines, the rest of the data showed low to no presence of possums.*
As you can see from the heat maps in Craig Bishop's presentation - rats are prevalent across many areas.
The indication of rats is higher in Kaipātiki than most Auckland suburbs, arguably due to the high proportion of native bush without adequate predator control.
The good news is there is noticeably lower incidences occurred in areas where reserves had a pest control programme. Tuff Crater for example had almost no rat browsing. (Congratulations to the Tuff volunteers - we hope this news brings you plenty of satisfaction!)
In areas with high rat numbers, for example the Uruamo headland (which includes Kauri Point, Centennial Park, NZ Defence Force land, Chatswood Reserve, Chelsea Estate Heritage Park and Chelsea Sugar) it was also evident that a reduction in rat indicators was evident where rat bait stations had been laid out by volunteers.
Possum indicators were much lower, however Craig says there may be more possums out there than the cards suggest...
*Chew cards can present a false indicator of the true abundance of Possums as rat browsing, which often destroys the Possum chew marks. This is backed up from preliminary analysis; which showed that most possum marks were found in areas where there were few rats found.
Further monitoring after our first round of rat control may provide a clearer picture of our possum population.
LEFT: Our youngest volunteers Rebecca Leyland-Penno with one of the more intact chew cards from Kauri Point. RIGHT: Hungry rats... many volunteers found cards like this. BELOW: A not-so-bright possum at City View reserve / Kauri Glen [Note: the peanut paste is only injected into two sides of the cards, so presumably this chap just liked gnawing]