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Road traffic noise causes bat activity to decrease by two thirds, as bats find it 'irritating' - University of Sussex

A new study has shown that road traffic noise causes bat activity to decrease by about two thirds and suggests that the negative effects could be felt considerable distances from the source.

Researchers from the University of Sussex conducted the first controlled field experiment to investigate the effects of traffic noise on both bat activity and feeding behaviour, working with five different bat species.

When recorded road noise was played, they found that the activity of all bats declined by around two thirds, with feeding behaviour also impacted.

Professor of Environmental Biology Fiona Mathews said: “Bats use special high frequency calls known as ultrasound to effectively ‘see’ in the dark using echolocation. We tested whether ultrasonic sounds from vehicles were the problem but actually found that most of the response was to audible noise. This type of noise resulted in aversive responses in all the bat species tested, whereas responses to ultrasonic noise were restricted to just a single species. Therefore, just like us, bats are likely to find audible road noise an irritation — something they would prefer to avoid rather than it jamming their echolocation. This is important as it means we could expect to see negative effects continue at a considerable distance from the road. We know that lower frequency road noise travels well beyond 50 metres – the scale at which ecological impact assessments are conducted.”

Road traffic is growing rapidly across the globe and predicted to double in the UK by 2050. For wildlife, this means increased risk of road traffic accidents but also wider effects due to light and sound pollution.

As reports show that the Covid-19 lockdown has caused road travel to plummet by as much as 73%, the researchers are now hoping to monitor whether bat activity around roads actually increases when traffic density is decreased.

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