ACOUSTIC BATTING

The bat cognoscenti know about the use of ultrasonic acoustic bat deterrents and recent developments in this field. However, those of us with less of a laser sharp focus on these nocturnal mammalian insectivores of our summer nights are not likely to be so familiar with the subject, so here is a little information for non-specialists.

Bats are (still, despite the Brexit threat) European Protected Species with full legal protection and strict liability for breaking the laws affecting them, so when new structures and lengthy building repair projects might or do harm them, there is a serious problem. Wind turbines, the construction industry and various infrastructure ventures such as HS2 present serious risks of bat mortality and a consequent need to keep bats away from them. Enter Natural England, ultrasound specialists and various ecological researchers, including a team from Bristol University, to work under licence to see whether and how ultrasound, which bats use to navigate and find prey, can also be used to keep them away from danger zones. That some moths can apparently deflect of jam a bat’s echolocating ultrasound made the researchers think it might be possible to use  a similar technique as well as generating a field of noise inaudible to humans and other mammals but uncomfortable enough do encourage bats to keep their distance.

A particularly interesting project has been the HS2 rail link corridor which passes along very “batty” habitat at various points where bats and fast trains would be a lethal (for the bats) contact. Wire mesh “tunnels” can divert the bats above and over the rail line but they can still fly in at either end. The researchers had to find out whether an acoustic deterrent device could discourage bats from a controlled area and the limits of such an area, whether there would be any collateral adverse impact on other wildlife and how to place the deterrents at the ends od the wire mesh tunnels for maximum effect.

After much research and field trials using infra-red recording and ultrasonic detection, excellent results were obtained with <98% deterrent success within 10m of the acoustic ultrasound generator units. So when (one day!) you are speeding along HS2 you will be able to be confident that bats will not be harmed because the track intersects their commuting flight paths in known favourite bat areas.

Plecotus auritus (Linnaeus, 1758) (brown long-eared bat) in one of our roosts. Photo: Betts Ecology.

Betts Ecology has done work on adverse bat interactions with wind turbines and many of our projects involve assuring the mitigation of negative impacts on bats in many different scenarios. On our sites we always encourage bats by providing roosts and plantings that favour their insect food.

 © Betts Ecology