Seeing bats flying around at sunset is becoming a lot harder to spot and apparently it's partly our fault.
While most of us like to sleep at night, bats sleep in the day and only get up when the sun starts to go down.
But because so many buildings and bridges are being lit up at night, the flying mammals are getting confused about when they should be coming out.
Now bat experts are asking people to count the bats they do see so they can keep track of the tiny creatures.
The Bat Conservation Trust will use the information from bat-spotters all over the UK to work out how many bats are left.
Pipistrelle bats are common in the UK
Bat expert Philip Briggs said: "We think we've lost a lot of bats because we've been losing the places that they feed and the places where they roost.
"There's a lot of lighting, which makes it unsafe for them to fly from their roosting areas to their feeding areas, so it's quite a difficult world for a bat to live in."
Dusk is a good time to spot the tiny critters as it's when there are lots of insects around, which are a bat's favourite food.
NR's Laura with the Scouts on bat patrol
Bat-lovers say it's important to keep track of the creatures because some of the 17 different types of bat in this country are already endangered.
Newround's Laura went on a bat-spotting patrol with a group of Scouts in London. Here's what some of them had to say about it...
Leonie, 9, said: "I think it's a bit of a shame, because humans like light more than the dark, but bats like the dark more than the light, so I think we should stop doing it for the bats."
Alexander, 10, said: "I'm a bit worried about bats because they are an endangered species and we have to look after them."
Katie, 10, added: "The way they catch their food and don't bump into trees by using really high-pitched sound is really interesting."