Possum/rat monitoring in small blocks

[David Wright]

I am advising landowners (e.g. conservation covenant holders) on management methods for generally small areas of forest.  It would be good to get some feed-back on the methods that people are using/finding most effective to monitor possums and rat abundance in small areas of forest.  Baring in mind the low level of experience and limited time that the majority of landowners have.  I have been advising most to use the wax block/tag method, but am not convinced of the accuracy and real benefits to be gained from this method, particularly in small forest areas (e.g. relatively limited area to run lines and small sample size) .  Cheers... 

[Bruce McKinlay]

Hi David,
I'd agree that in small patches of forest wax tags which are after all presence/ abscence indicators are weak in determining abundance.  When you say abundance how much detail are you after?  It could well be that in small areas all you are ever going to get is presence/ abscence.  For possums and rats I think kill trapping with Timms and snap traps under tunnels are goping to be your best bet.

[David Wright]

Thanks Bruce.  I guess that I should have mentioned that the general size of the small blocks that we are monitoring are 20-40 hectares.

[Jamie MacKay]

Wax tags are great for telling you what is about and are cheap and easy to put out. For abundance I agree that trapping is the way forward. I think it is worth trying to match your methods as closely as possible to standard index trapping methods and keep good records - it is easy enough to do and could end up being useful in the future.

[Malcolm Thomas]

I developed WaxTags specifically as a safe method for possum monitoring where kiwis are present unlike traps which can maim or kill kiwis. Recent research results show that they can accurately predict possum abundance as well as presence absence. If you want more information and download reseach reports visit Pest Control Research's web site at www.pestcontrolresearch.com

[David Wright]

Hi Malcolm - it's David Wright here, I worked for you at Landcare Research while I was a Lincoln student in the mid-90s (cat bait station research).  Thanks everyone for the replies.  I guess the info/discussion that I wanted, was the best monitoring method for small block owners with limited experience and time (e.g. probably not being able to/have the area to run long lines or have the number of replications required for robust results). We still need an indication of approximate abundance for management, particularly as a lot of the work on these small blocks is funded by Regional Council/Biodiversity Condition etc... funds, and therefore needs to be reported on back to the funding agencies.  Cheers

[Malcolm Thomas]

Hi David,

Yes I remember you David. Since 2000 I have been in private research and one of my achievements is the developemnt of a nationally NPCA protocol supported possum monitoring method using WaxTags. The method is ideally suited to small blocks and community groups because it does not require the capture and killing of animals which some peopl do not like doing. As mentioned previously it does not threaten ground birds. I have done a lot of research looking at how well the bite-mark index BMI relates to possum density. The results indicate there is a very good correlation between possum density and BMI.  Have a look at http://www.pestcontrolresearch.co.nz/research-monitoring.htm#2 for a copy of the report comparing BMI with possum desnity. The method also could provide an indication of rat density but there has been no research conducted to test the BMI against rat desnity. Overall the WaxTag method would be ideal for people without much experience in setting traps etc. Hope this helps. Feel free to contact me at info@pcr.co.nz if you want more detailed information on monitoring designs.

[Alicia Warren]

I am assisting Friends of Oakley Creek monitor and control rodents and possums in Oakley Creek, a suburban reserve in Auckland.  The area is a corridor of about 20 ha.  I selected tracking tunnels for monitoring rodents and waxtags for monitoring possums as simple techniques that volunteers could conduct, and with a bit of training can also interpret the results.  For rodent control I selected diphacinone baits in Protecta Sidekick bait stations , and for possum control cholecalciferol in bait bags on trees (higher than normal so out of reach of dogs).  Malcolm was very helpful in showing me how to identify bite marks on waxtags. 
Our first waxtag monitoring prior to any poisoning indicated high levels of possums, e.g. 40% of waxtags showing possum bite marks.  We are aiming to reduce possum bitemarks to 5% through our possum control.
There is quite a bit of overlap between monitoring methods.  For instance, a few tracking tunnels baited with peanut butter have possum prints on the cards, and a lot of the waxtags have rodent bitemarks on them.  Which leads me to wonder whether waxtags might be an effective rodent monitoring tool as well?
Regards
Alicia

[Mark Bellingham]

I agree with Alicia, wax tags for possums (although traps will monitor and kill them) and tracking tunnels for the others.

But the easiest way to get rid of possums and rodents is with 50x100m spaced bait stations and Pest-off pellets in 100g doses in thin sealed plastic bags (available at the local hardware store or farm supply place). We keep rats at 0-1% density over 50 private land blocks and 1500ha of regional park (Ark in the Park) with this method. The bags lessen any spill and keep the baits from going mouldy. Works a treat, & no evidence of residual effects, resistance etc.