Predator management is reliant on luring, for both trapping and detection purposes. Fatty, protein-rich lures such as Pic’s™ peanut butter, Nutella™ and egg mayonnaise are known to be highly attractive to predator species such as possums, rats and stoats. However, these lures do not last well in the field and so their use carries a high labour burden.
Long life lures – such as blocks infused with food scents – have also been developed, but unfortunately in our experience tend to be much less attractive than their fresh counterparts.
Seeking the best of both worlds – a highly attractive lure with a low labour burden – we teamed up with inFact (a Christchurch-based mechanical and engineering company) to develop an automated lure dispenser capable of dispensing a fresh food lure every day for up to one year, without requiring manual service.
Introducing the ZIP MotoLure
The ZIP MotoLure can be affixed to trees or trap lids, and comprises:
a stainless-steel chassis;
a motor driver (with an anticipated five-year battery life);
a motor bolt; and
a 60 ml syringe containing a fresh food lure (currently egg mayo)
Partial rotation of the motor driver each day forces the bolt to depress the syringe, and extrude a pre-programmed amount of lure. Each syringe is sealed from the elements, so the lure remains fresh up to the point of dispensing. In testing our prototypes, we identified four key applications for the ZIP MotoLure.
APPLICATION 1:
A lure for traps
Typically, a field ranger is required to manually refresh the food lure in a trap every 3–4 weeks, to maintain lure effectiveness. The associated costs limit the scale at which trapping can be carried out – particularly in difficult, remote terrain.
By eliminating the need to manually refresh lures, the MotoLure is expected to improve trapping effectiveness and efficiency by:
consistently providing fresh lure, even when non-target lure take occurs
massively reducing the costs of running a trapping programme; and
allowing larger project areas to be trapped – especially when paired with a remote reporting system.
We first trialled this approach in the Perth River valley. While rats were the target species, we also caught over 20 stoats in seven months.
BELOW: By slightly modifying a standard trap box lid, a MotoLure can be installed horizontally, allowing fresh lure to drip down through the lid
APPLICATION 2:
A pre-feeding tool
The MotoLure can be used as a stand-alone device, to cue target animals onto a lure through safe food association. This application can be used to:
increase trapping effectiveness of a virtual barrier of traps; or
increase the chance of trapping invaders within a protected area.
RIGHT: A ship rat feeding at an early prototype MotoLure at the Bottle Rock field site
ABOVE: Results of a 9-month Bottle Rock pre-feeding trial on trap catch rates, demonstrating that the treatment prefed with MotoLures caught 38% more rats than the control
APPLICATION 3:
A bio-marking tool
The MotoLure has been used by ZIP in the Perth River valley to both prefeed and bio-mark rats, in order to observe their movement through the landscape. We tested the bio-marking capability of the MotoLure by:
mixing 1% rhodamine B into the mayonnaise lure, and installing MotoLures along an uncontrolled river margin; then
trapping for rats along the same margin one month later
We found that 82% of rats caught were marked with rhodamine B! This was a good result, as it meant we had found a method of achieving passive, continuous marking, with very little effort.
We observed the subsequent movement of marked rats by:
continuing to mark the population;
trapping for rats using MotoLures on trap boxes on the far side of the river; then
analysing caught rats for traces of rhodamine B
Over seven months, one rat was trapped on the other side of the river with biomarker present in its system. Whisker analysis revealed that the rat had consumed the biomarker at least twice in the last 50 days (two fluorescent bands were visible in several whiskers).
ABOVE LEFT: A MotoLure in the Perth River valley laced with rhodamine B
ABOVE RIGHT: A rat showing external signs of recent rhodamine B consumption around the mouth and belly fur
ABOVE: Bands of rhodamine B fluorescence (outlined in red) found in whisker samples from the rat identified as having crossed the river
APPLICATION 4:
A lure for a highly sensitive detection device
Luring is well known to increase encounter rates with devices used for detection of predators. When paired with a trail camera, the MotoLure can be used to attract possums, rats and stoats into a camera’s field of view – and has the advantage of encouraging repeat visits by providing a food reward.
In the Perth River valley, we have used this application to target stoats in particular, which are difficult to quantify at low density.
Standard three-night tracking tunnel methods detected a stoat in only 1 tunnel out of 60 (1.7%).
Over the same area, cameras at 1/35 ha were paired with MotoLures.
After three weeks, 41% of the cameras detected stoats, of which 46% detected stoats on multiple days.
Future Directions
Using Artificial Intelligence (A.I.) Cameras with MotoLures
We are currently in the process of building cameras with on-board A.I. to record, sort and identify images of invader predator species. We expect these cameras to be paired with the ZIP MotoLure.
This combination, coupled with remote reporting to notify field staff of a predator detection, is likely to greatly increase the efficiency and effectiveness of any response effort.
Other Food Lures
We know that Pic’s™ peanut butter is a highly attractive food lure for rats, and was the first lure we attempted to dispense from the MotoLure in the field. Unfortunately, we found that the oil and solids separated over time, leading to blockages in the dispenser. Egg mayonnaise has the ideal viscosity, and a relatively high level of attractiveness to possums, rats and stoats. We have had much success using egg mayonnaise, but realise the importance of being able to use more than one effective lure. To that end, we are now working with Massey University to create a recipe using Pic’s™ peanut butter that will be suitable for MotoLure dispensing. Watch this space!
ABOVE: MotoLure trials with Pic’s™ peanut butter resulted in hardness and clogging from oil separation
The ZIP MotoLure was researched and developed with the generous support of NEXT Foundation, Department of Conservation, Predator Free 2050 Limited, Jasmine Social Investments and Morgan Foundation. This support has also enabled us to begin producing and supplying this tool to others in the conservation community.