Auchnerran: using lasers to control mammalian pests

Using lasers to control mammalian pests

One of the lasers in action on a partner site. ©Liverpool John Moores University

BACKGROUND

The Laser Fence project was part-funded by the EU LIFE+ programme and led by Liverpool John Moores University, with GWCT, Bird Control Group (Netherlands), Iris Drone Specialists (Spain), Volterra (Spain) and Angel Camacho (Spain) as partners. It ran from 2016 and finished in September 2020, with the final report submitted at the end of December. The standard lasers used in the trials were classed as 3B: this is an international rating indicating that the lasers are potentially damaging to eyes. This influences the manner in which they can be used and a risk assessment must be produced before deployment. The Laser Fence project aimed to test a commercially available laser bird-scaring system on mammalian pests of agricultural crops and food stores. The movement of the laser spot across the substrate scares the animals away – it does not need to touch them at all. It was hoped that this might provide a non-lethal alternative to rodenticides and traps under certain circumstances. This project is now finished and this article reports some of the findings from Auchnerran.

The GWCT ran trials at Auchnerran focused on rabbits and rats. The laser system came as a handheld device or a standalone, programmable unit which could run from a large battery charged via solar panels, offering the opportunity to have the laser running in a particular area for long periods of time. The standard colour for both was green. The handheld lasers were used to explore behavioural responses, mostly of rabbits, to the laser beam shone on the ground close to them, while the standalone option was ideal for testing whether the laser could keep animals out of areas where the laser was projected.

The standalone devices quickly became almost useless for our purposes when the Health & Safety Executive (HSE) deemed them unsafe to use in the open while unsupervised, despite recognising the extremely low probability of someone damaging their sight from exposure to the beam (which is constantly moving). Results from these trials are not mentioned further; instead we focus on the behavioural responses of rabbits to the handheld laser.

There are few published data on the efficacy of lasers on birds, but the manufacturer and many users report high response rates, with birds quickly leaving an area when a laser is used. It was clear early on that this was not the case for mammals, which were more circumspect in their reactions. The proportion of tested rabbits that showed one of several ‘fear’ responses to the green handheld laser when it was projected nearby in the evening (low light levels but not dark), varied between approximately 20% and 36% once background activity levels were taken into account (as indicated by control-rabbit responses) across all trials.

Rabbit responses to the green handheld laser beam were not impacted by the pattern, speed or duration of laser movement. This suggests that no complex style

of laser presentation is needed to produce a measurable response in rabbits. A 12% response rate among rabbits (after controlling for background activity levels) was detected at a green laser power output of approx. 0.4 mW (which produces a relatively dull light). This was around half the response rate achieved with the 450 mW output in the same trial. This suggests that low-powered laser emissions may have some potential as a deterrence after dark (ie. very low light levels). If confirmed, this would mean the HSE restrictions on automated use of lasers would not apply to this safe output level – an important milestone if this is to become a practical tool. Green and blue lasers were found to be equally effective at eliciting a fearful response from rabbits at dusk (36-42% response rate), more so than yellow and red, although the yellow handheld laser had a lower power output (100 mW vs 450 mW).

These results, coupled with the findings from the partner trials which suggest habituation to the laser is minimal over the course of a month or two, suggest the response of mammals to the laser is not as clear-cut as for birds, but does offer hope that it may be possible to develop a system that will deter some pests from defined areas under perhaps limited circumstances. More trials are planned to explore this further at Auchnerran as part of the follow-up ‘After LIFE’ project.

Green and blue lasers were found to be equally effective at eliciting a fearful response from rabbits at dusk, more so than yellow and red. ©Peter Thompson

KEY FINDINGS

A moderate proportion (20-36%) of rabbits showed a range of fearful responses to the green laser irrespective of the speed and pattern of laser movement.

A small response rate (12%) was found even to the low-powered laser (ie. producing a relatively dull light), raising the possibility that this safe laser output might be useful at deterring rabbits after dark.

Blue-coloured lasers had a similar deterrent effect on rabbits to the green laser.

Further work is needed to test whether the moderate response rate detected in trials (replicated among the project partners) might form the basis of a practical deterrence system to protect crops and food stores from pests.

Dave Parish Marlies Nicolai

Introducing the project to visitors at the GWCT Scottish Game Fair. © GWCT