Bats cross roads regularly as they use diverse parts of their habitat area and cover more territory than most other small mammals. They forage for food each night, and commute to different locations for mating, breeding (maternity and nursery sites), roosting and hibernation. Roads are recognized as a source of habitat fragmentation and disruption (when road construction removes features like roost sites or affects habitat thus reducing insect diversity) but a first of its kind study at the University of Exeter found that roads are a serious threat that directly affects bats.
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The research found that bats are reluctant to cross roads, interfering with their ability to reach feeding and roosting areas and that direct collisions with vehicles result in at least 1,000 bat deaths per year. Roadkill bats are difficult to find due to their small size, so scientists believe actual mortalities are exponentially higher. More male bats than females are killed, perhaps due to how they compartmentalize the habitat, with females sticking together in breeding sites near prime habitat, thus forcing the males into less favorable areas close to roads. Bats are more likely to cross roads with trees along the road edge, but this also increases the rate of collisions. Researchers speculate that roads with some tree canopy cover may force bats to fly higher, reducing collisions because the bats remain high above traffic.
Solutions to these problems include green bridges above roads and underpasses at points identified as bat commuting routes. These accommodations would also help other wildlife safely move across the roads. Studies conducted prior to road design and construction must give more attention to bat impacts and incorporate plans that reduce these impacts as the mortality rates are especially dangerous to rare and endangered bat species. Lead author Dr. Fionna Mathews says her research indicates that there is
“no cause for complacency” in terms of the protection offered to bats in the UK and Europe. “We need a lot more consistent research on the real effects of road-building on bat populations. It is not enough to spend a lot of money on bat surveys if they are not carried out scientifically and consistently. We need to know a lot more about how roads affect bats.
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