Study type: Medical/biological study (experimental study)

The aversive effect of electromagnetic radiation on foraging bats: a possible means of discouraging bats from approaching wind turbines. med./bio.

Published in: PLoS One 2009; 4 (7): e6246

Aim of study (acc. to author)

To test the hypothesis if an electromagnetic signal from a small portable radar can exert an aversive response in foraging bats and aerial insects.

Background/further details

The study was performed to test whether radiofrequency electromagnetic fields could be used as a method of preventing bats from death caused by collisions with wind turbines. From June to September 2007 bat activity was compared at 20 foraging sites in northeast Scotland during experimental trials (radar switched on) and control trials (no radar signal). The order of trials were alternated between nights.
From July to September 2008 aerial insects at 16 of these sites were also sampled.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
  • unspecified
Modulation type: pulsed
Exposure duration: continuous for 20 hr (bat activity) or 16 hr (insect count)
Exposure 2:
  • unspecified
Modulation type: pulsed
Exposure duration: continuous for 20 hr (bat activity) or 16 hr (insect count)
Exposure 3:
  • unspecified
Modulation type: pulsed
Exposure duration: continuous for 18 hr (bat activity) or 16 hr (insect count)

Exposure 1

Main characteristics
Frequency
  • unspecified
Type
Exposure duration continuous for 20 hr (bat activity) or 16 hr (insect count)
Modulation
Modulation type pulsed
Pulse width 0.08 µs
Duty cycle 1.68 %
Repetition frequency 2,100 Hz
Exposure setup
Exposure source
Setup antenna placed on a platform 2 m above ground level
Parameters
Measurand Value Type Method Mass Remarks
power 6 kW peak value - - -
electric field strength 5.58 V/m peak value measured - at a distance of 10 m
electric field strength 5.11 V/m peak value measured - at a distance of 20 m
electric field strength 3.79 V/m peak value measured - at a distance of 30 m

Exposure 2

Main characteristics
Frequency
  • unspecified
Type
Exposure duration continuous for 20 hr (bat activity) or 16 hr (insect count)
Modulation
Modulation type pulsed
Pulse width 0.08 µs
Duty cycle 1.68 %
Repetition frequency 2,100 Hz
Exposure setup
Exposure source
Setup antenna placed on a platform 2 m above ground level and fixed so that the signal beam was directed towards the area of the highest bat activity
Parameters
Measurand Value Type Method Mass Remarks
power 6 kW peak value - - -
electric field strength 26.24 V/m peak value measured - at a distance of 10 m
electric field strength 22.99 V/m peak value measured - at a distance of 20 m
electric field strength 20.25 V/m peak value measured - at a distance of 30 m

Exposure 3

Main characteristics
Frequency
  • unspecified
Type
Exposure duration continuous for 18 hr (bat activity) or 16 hr (insect count)
Modulation
Modulation type pulsed
Pulse width 0.3 µs
Duty cycle 3.6 %
Repetition frequency 1,200 Hz
Exposure setup
Exposure source
Setup antenna placed on a platform 2 m above ground level
Parameters
Measurand Value Type Method Mass Remarks
power 6 kW peak value - - -
electric field strength 25.52 V/m peak value measured - at a distance of 10 m
electric field strength 18.68 V/m peak value measured - at a distance of 20 m
electric field strength 17.67 V/m peak value measured - at a distance of 30 m

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Bat activity and foraging effort were significantly reduced during experimental trials when the radar antenna was fixed to produce an unidirectional signal therefore maximising exposure of foraging bats to the radar beam. However, although bat activity was significantly reduced during experimental trials, the radar had no significant effect on the abundance of insects captured by the traps.
However, although bat activity was significantly reduced substantial numbers of bats continued to forage within the radar beam. It is possible that only a particular combination of wavelength, pulse repetition rate and power output may provoke a reaction.

Study character:

Study funded by

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