Our Remote Sensing Trial

By Paul Callister

October 2019

Our remote trap sensing project started with a typical New Zealand style chance meeting. My sister came across the great experimental work Matt Way and Scott Sambell from Econode were doing with remote sensors at the Glenfern fenced sanctuary on Great Barrier Island. This was soon followed by a discussion over coffee when Matt and Scott were passing through Paekākāriki.

Luckily this meeting took place just as we were beginning to create a Kāpiti Mainland Island as part of the Ministry for the Environment’s Kāpiti Coast Biodiversity Project. We were able to draw on some of this funding to begin our experiments.

Phase one of the trial began in August 2016. It was a collaboration between Ngā Uruora (on behalf of the Kāpiti Biodiversity Project), the Paekākāriki firm Groundtruth (who run Trap.NZ) and Econode. This initial seed money did not fully fund the research effort so we relied heavily on the goodwill of the partners. Supporting this was also a considerable amount of volunteer time provided by the trapping community.

While there was potential to use this technology on a range of traps, it was initially decided to restrict the trial to DOC200 traps and box based rat traps (Snap-e type traps).

In late 2016 13 remote sensor traps were placed in a range of locations across Queen Elizabeth Park, Paekākāriki and the escarpment. Initially these traps were monitored through an internet connection that provided a table which indicated if the trap had sprung. An additional layer of the table showed when the trap was sending a signal and also when the trap was sprung or was set.

The first part of the trial took place when there were relatively few mustelids or rats being caught. Our first catch was a mouse that set off a trap that was then located at Queen Elizabeth Park. Subsequently, a small number of mustelids were caught.

By December 2016, the data from the Econode remote sensor traps was fully integrated with the Trap.NZ system. This was due primarily to the work of Daniel Bar-Even. This was achieved using an API (application programming interface) that works with the web service provided by Econode.

From the user’s perspective adding a sensor powered trap to a Trap.NZ project was simply an extension to adding a normal trap. The only difference was the trappers enter the address of the sensor (a unique code that each radio has), the trap then automatically shows up within the project as a “smart trap” and indicates its status within Trap.NZ reports and maps. Within Trap.NZ additional information is provided for the smart traps such as: sprung state, battery state, signal strength, last communication time, etc.

One very positive outcome of this development work was that the API can be adapted easily to be able to work with other networks and radio trap sensor systems as they become available.

Since this early development work, the Trap.NZ system has been adapted to send out messages on events – there is now a simple interface that allows users to select (via their account preferences) to optionally have notification emails and/or text messages sent whenever a sensor trap is sprung.

While there were some excellent outcomes for phase one of the experiment, the trial also threw up some challenges. The first was equipment failure. It was a very wet and windy spring in the first year and this provided a difficult environment. The early sensors were not fully waterproof. Based on feedback from our experiments, Econode developed new, better sealed sensors.

An equally important challenge has been that the LoRa technology only works well with line of sight radio coverage. LoRa is a Long Range low power wireless communications technology. The radio waves can bend around corners to some small degree but overall it is not well suited to sending signals into tight gullies or around ridges. This is the type of topography both Whareroa Farm and the escarpment is made up of. In addition, the radio waves have some difficulties penetrating thick forest cover. These challenges can be overcome with repeater stations and these are currently under development. The trial suggested an offshore aerial covering the mainland would allow much bigger area of the Kāpiti Coast.

With funding from a GWRC grant given to the Kāpiti Coast Biodiversity Project, an aerial was placed on Tokomapuna Island This has worked well. But the location is not much above sea level. We are now planning to move the aerial to the top of Kāpiti Island. Not only will this give greater coverage of the Kāpiti Coast, its location means traps in the outer Marlborough Sounds as well as Southern Taranaki could be monitored.

Sensor traps were placed in our lizard protection trial. The ability to collect fresh mustelids allowed us to determine that indeed weasels were eating our lizards.

We have been able to extend our research using a further DOC grant. This allowed us to buy new versions of Econode sensors for DOC200 traps. These now have the sensor inside the trap rather on top of it. This gives it better protection.

But as part of the development of the ‘mainland island’ a small network of Goodnature A24s (targeting rats) and lizard related A24s (targeting mice) had been installed. The standard way of determining how these are performing is to install relatively expensive counters. We have trialled Econode sensors on some of these traps. They not only give a count of kills but also give additional information on when the traps triggered. Is this during the day or night, is it soon after new lures are installed or does it take place over an extended time?

We have also trialled another brand of sensors. These are produced by Motiv and are motion sensors. A small trial of these is currently underway at Ngā Manu and some have been trialled at Whitireia Park. Again we have had significant waterproofing problems with early models. In addition, motion sensors seem to give some false alerts if the trap is bumped or even affected by heavy rain. We see that a number of other sensors are now entering the market.
Cats are a problem on a number of our sites and elsewhere live catch traps have been deployed. Glenfern had already been using remote sensors to signal when such traps have been sprung on Great Barrier Island. As yet we have not used sensors in this role but are keen to learn how other groups use them.
When we started these experiments we thought there are a number possible uses of the remote sensing trap technology. These included:

• Having an automatic log of when traps go off (what day, what time of day). Potentially these data could analysed that data against a range of variables such as weather conditions.
• If researchers are wanting ‘fresh kills’ for dissection work (for example determining what predators are eating) trappers can quickly get to these.
• Early detection of intrusions into a protected area. This could be an intrusion into a predator fenced area, an offshore island or perhaps an area that needs special protection (for example penguin or kaka nesting).
• If contractors are servicing trap lines it gives an independent record that all traps are checked.

The sensors have been especially useful in obtaining fresh specimens for autopsy. Through this we have had confirmed that weasels are important predators of lizards.

We have also found some traps are very active. One particular trap on the escarpment seems to catch considerably more rats that others in the area. Without sensors we would have not known this.

When we started the experiments we had in mind their value in monitoring traps way out in the bush. We now realise some of their best use is in high value sites close to where we live. If we know a trap goes off we can quickly walk or bike to the site and clear the trap. That way the trap is constantly set.

There are however problems still to be overcome. These are bespoke systems so sensors remain expensive. There are also ongoing monitoring costs. There also remain questions as to how long these even improved sensors will last in the challenging areas we work. Changing batteries in the field remains a challenge. For the moment conservation groups need to consider very carefully the costs and benefits of using sensor technology.

Ngā Uruora is confident that the ‘internet of things’ has much to offer in terms of increasing the productivity of our conservation efforts. We are pleased that we have had the opportunity to play a small part in the ongoing development of remote sensors for traps.