Bats and Windfarms

Radar as a method of

mitigation ?

*P.A. Racey & B. Nicholls

*School of Biological Sciences, University of Aberdeen, U.K.

Bats and RadarBats and Radar

1. Anecdote: No bats in vicinity of Aberdeen airport radar.

2. Pilot Project: Significantly fewer bats in vicinity of two Scottish airport

radars compared with sites matched for altitude and land use.

3. 2006 Project: To test hypothesis that bats avoid electromagnetic radiation

associated with radar installations.

Mitigation:

Birds: visual deterrents

Bats: Acoustic deterrents ???

Radar ?

Biological Effects of Biological Effects of

Electromagnetic Fields (EMF)Electromagnetic Fields (EMF)

1MHz – 300GHz: Thermal burden

Perception Aversion Thermal insult Death

Auditory microwave hypothesis: Thermal expansion

Thermoelastic wave sound pressure wave excitation of auditory neurones

Auditory response:

Humans: 13kHz

Cats: 38kHz

Rodents: 45kHz

Civil Air Traffic Control

(n=4)

Weather

(n=3)

Military Air Traffic Control

(n=3)

10 Radars: 300MHz 10 Radars: 300MHz –– 15GHz15GHz

Radar

a1

b1

c1

High

(>2v/m)

Medium

(<2v/m)

Control

(0 v/m)

Electromagnetic field

strength

Sampling protocol

c2

b2

a2 a3

b3

c3

10 radar sites, 9 samples in each: 3 high, 3 med,

3 low. Total = 90 samples, 30 in each group.

Sampled for bat activity, species and feeding

buzzes.

Three sites sampled contemporaneously

each night. Sites paired for: altitude,

latitude, landclass, habitat type,

connectivity and habitat structure.

Frequency division

transect: 30mins

Frequency division

transect: 30mins

Frequency division

transect: 30mins<200m 200 - 400m >400m

Results: high EMF vs control

Bat active minutes

(paired t test, n = 30, p<0.001)

Bat passes

(paired t test, n = 30, p<0.001)

-1.5

-1

-0.5

0

0.5

1

Civil ATC Military ATC Weatherlo

g (

hig

h E

MF

bat

acti

ve

min

ute

s +

1)

–lo

g (

con

tro

l b

at

act

ive

min

ute

s+1)

-2

-1.5

-1

-0.5

0

0.5

1

Civil ATC Military ATC Weather

log (

hig

h E

MF

bat

pa

sses

+1)

–lo

g (

con

tro

l b

at

pass

es+

1)

Results: Intermediate EMF vs control

-2

-1.5

-1

-0.5

0

0.5 Civil ATC Military ATC Weather

log (

med

ium

EM

F b

at

act

ive

min

ute

s +

1)

–lo

g (

con

tro

l b

at

act

ive

min

ute

s+1)

-2

-1.5

-1

-0.5

0

0.5

1

log (

med

ium

EM

F b

at

pass

es +

1)

–lo

g (

con

tro

l b

at

pass

es+

1)

Civil ATC Military ATC Weather

Bat active minutes

(paired t test, n = 30, p=0.004)

Bat passes

(paired t test, n = 30, p<0.001)\

ConclusionsConclusions

• Bat activity was reduced in habitats exposed to electromagnetic radiation.

• However without access to detailed specifications of individual radar units

(including operational times and operating frequency) it is difficult to quantify this relationship further.

Way ForwardWay Forward

• To more fully define the impact of radar on foraging bats, and ascertain its

value as a potential source of mitigation, field trials involving a mobile radar that can be introduced into areas of known bat activity are now required. If the parameters of an RF signal capable of inducing an aversive response in foraging bats could be characterised then this may offer a method of mitigating bat collisions with wind turbines.

ACKNOWLEDGEMENTSACKNOWLEDGEMENTS