I live in an area of indigenous forest (both old and regenerating), where mammal pest control is taking place.
However, the area is completely overrun with plague (rainbow) skinks - to the point which you could almost say it’s an infestation. I also know we have geckos in the area, as there have been multiple sightings nearby.
So it seems kind of ridiculous to be on this awesome land, on which there are likely endemic geckos and maybe endemic skinks, and not do anything about the massive population of invasive skinks.
So my questions:
Would I be correct in assuming that the plague skinks are competing with the native herpetofauna?
Have there been any attempts at controlling or eliminating plague skinks in the past?
Are there any techniques that are known to be effective at eradicating or controlling plague skink populations?
I don’t know about skinks specifically, but I do know that many attempts to eradicate an unwanted species has caused more mayhem and pain than the species they are trying to control.
Many attempts are not even trying to eradicate the unwanted species, but simply keep them “under control”, thus requiring an almost never ending effort into keeping their populations down.
There has to be a really good reason for eradication or large scale control, in order to try to tackle an unwanted invader.
Since the mammals burning through the wildlife of Aotearoa are the ones getting most of the attention (justifiably), there isn’t as much work on reptiles, but there are efforts elsewhere that are being observed and beginnings of controls put in. There were a few studies out of Massey a couple years back testing on a new incursion on Aotea that found trapping to be relatively ineffective and proposed instead baiting with paracetamol following the lead of efforts in Guam and Florida. Paracetamol is lethal to many reptiles, plague skink included, and is not persistent in the environment, so could be something pursued if there’s a way to put in a management scheme for it that doesn’t also affect the native reptiles.
For now it’s much more focused on preventing spread since they have only really established strongly in the northern bit of the North Island, and efforts being so much more urgent and publicised for the mammals.
So to directly address the questions
Yes you are correct in the competition and they also decimate local native inverts like weta, but possibly the larger issue is that they make really good food sources for invasive mammals so can worsen the local mammalian situation.
As above
As above
Just personal opinion- resources can be better spent elsewhere, but where there is low-hanging fruit like just preventing incursions on plague skink-free islands and limiting spread outside of the current areas, definitely should be thought of as part of the whole suite of biota-destroyers to be accounted for.
@intyrely_eco makes some greats points. I’ve not worked with this skink or on NZ, but have worked with invasive lizards elsewhere. It’s really difficult to eradicate any small lizard from an area, even a really small island (like less than an acre). It is possible, but generally requires a really intense, personpower heavy effort over a long period of time. In a contiguous area without hard boundaries, it becomes near impossible. Keeping numbers low is possible if that’s valuable for some reason (but in my opinion it rarely is).
Effort is definitely best spent on prevention or immediate fast response once the first/one few individuals are seen in an area. Once established, there’s a really good chance control efforts/resources are better put elsewhere.
There are no established management or eradication methods at this stage. Plague skinks tend to thrive in urban areas. As their populations have increased, more and more people in cities such as Auckland have reported plague skinks entering their homes and taking up residence. This poses a potential risk to human health, as lizards are known to be carriers of diseases including Salmonella and Cryptosporidium.
Anecdotally, I have heard that chickens were used as a control on a plague skink outbreak on Great Barrier Island. This was not a complete success, but plaque skinks were kept to low numbers there.
I live on the Russell peninsula, Northland. Approximately 3500ha.
Since 2002 possum and stoat numbers have been substantially reduced by ongoing pest control. The endangered North Island Weka was reintroduced in 2002. There is now a substantial population of weka on the peninsula. Substantial numbers of plague skinks have been reported at Rawhiti, to the east of Russell, where no weka are present, To date I know of no established plague skink populations on the Russell peninsula itself. (They have surely arrived here. During building work I was recently doing I saw what I am certain was a plague skink escape from timber that had just been delivered, sourced from outside the peninsula, to the work-site).
I propose that it is likely that weka are acting as a control of plague skinks on the Russell peninsula. This is by predating both the adults and their eggs. (NZ lizards, apart from one off-shore island species, give live birth to their young. They don’t lay eggs).
Incidentally kiwi numbers, we hear them every night now, have also increased substantially during the last 18 years of predator control.
That’s a nice new take, thank you @linds-nz
Yes I heard about the chickens - creative strategy!
The weka performing a similar role is an interesting concept. Definitely food for thought - put’s things into a more ecological perspective.
Responses on this topic have indicated that it would currently not be worthwhile to attempt any direct control of the plague skink situation. So now it’s more a question of what indirect actions could be taken to remedy the situation? If I wanted to help, it looks like there would be better ways to tackle this than going for it head-on.
Instead, perhaps increasing mammal pest control for the (maybe eventual) reintroduction of indigenous species such as the North Island Weka? Or (legally) establishing captive breeding populations of endangered species indigenous to the area? Or even entering into research in this field.
Yep.
Don’t equate weka with fowls.
Weka are not chooks!
They are much smarter and will really focus on a proven food source.
As an experiment I left plague skink eggs out in a high sided box, monitored by a trail camera. The nest was arranged like the only photo of a plague skink nest I could find.
I knew weka were around.
It is likely that the birds had never seen plague skink eggs before.
The plague skink eggs lasted a total of 4 minutes after I left.
The main impediment was the high sides of the box!
See Plague Skink nest & weka.avi (dropbox.com)
@linds-nz that’s awesome!
I can’t seem to view the dropbox link, but that’s alright - It sounds brilliant.
You indicated that there has been possum and stoat pest control on your land - do you know any methods to be particularly effective?
I don’t claim any expertise with predator/pest control.
The DoC 200 trap set in a box with two mesh covers and offset entrances are used for stoat control. There are recommendations online, such as the Predator Free 2050 website as to how to set them up. Stoats are tricky. I caught one in a trap with no bait inside to attract it in. Go figure.
My trail cameras are very good at alerting me to possum presence. We have very few now, with landscape possum control across the peninsula. I use traps and occasionally bait to get 'em. I have experimented with the Goodnature A12 and the NZ Autotrap AT220 repeat kill traps. The AT220 worked well (killing rats) until the lure stopped being extruded. A rat also became smeared across the pressure plate and deterred further rats. The lesson? Repeat kill traps have got to be checked regularly.
Pest control is a really specialised field, requiring dedication, experience and an understanding of the species targeted.
There are many people out there with far more knowledge than me.