|"Hello? Anyone there?"|
If you have a large population of pests, say possums, and you place a device in the field, chances are that some individual possums will bump into the device simply because there are so many possums about. After a control operation when the possum population has been reduced dramatically, there is much less chance of the remaining individuals finding your device. There are several tricks by which you can increase the chances of an encounter. There could be a colour or a scent added, for example. One of the difficulties with these methods, especially in forest, is that these lures only work over short distances. One potential method to provide a larger zone from which to draw a possum to your device is to use sound.
Matt Kavermann has just completed a PhD where he looked at the potential of sound to act as a lure to stimulate possums to come to a site and to interact with a device, like a bait station or waxtag. Possums are curious animals and when they find something unusual in their territories they will generally investigate it (which usually means biting it thoroughly). Matt, with his supervisors James Ross and Adrian Paterson, developed several generations of devices that produced audio lures (usually a high-pitched beep). The idea was that a possum would hear the noise from a distance and be guided to the waxtag or chewcard which they would bite and leave evidence of their presence. To test this idea, Matt set up an experiment in beech forest at Mount Misery at the south-eastern end of Lake Rotoiti in the Nelson Lakes National Park. Matt had 48 monitoring sites located in a 150m x 150m grid. Half of the sites had the audio lure (a beep every 15 minutes)and half were silent. At each site Matt had a waxtag or a chewcard to record possum presence. Matt checked these sites daily for 10 days. Given the terrain, it's not called Mt Misery for no reason, this was a huge effort.
Matt's results have just been published in New Zealand Natural Sciences. Matt found that the audio lure increased possum detection at chewcards by 30% and at waxtags (which are not as sensitive) by a whopping 900%! There was evidence that the audio lure was dragging in possums from over 300m away to the detection site. It appears that possums do hear the lure and are curious about what is causing it. They move to the source of the sound and are more likely to interact with the device placed there. This is excellent news for possum control. Audio lures may be a great way of counting how many possums survive an intense control operation. Better yet, audio lures may provide a way to target these remaining individuals to reduce pest populations to zero by encouraging them to move to a site with toxic bait. The pied piper was able to remove all of the rats from Hamlein by playing his music. Maybe he was onto something!
|"I'm sure that sound came from over here"|