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Cat owners are being asked to keep their pets indoors to protect bats, birds and other creatures.

According to the Bat Conservation Trust, cats watch the bats to find out where they live before returning later to hunt them.

Wildlife conservationists say that a curfew to keep cats indoors after dark will improve the numbers of bats and other vulnerable species.

"It can really make a big difference," says Beth Gerrard of the University of the West of England.

Bats are the only mammals capable of flying, not just gliding.

There are 18 different types of bat species in the UK with four considered "vulnerable" and two described as "near-threatened".

Endangered bats include the greater mouse-eared bat, often known as Britain's loneliest bat.

It was declared extinct in England in 1990, before reappearing 20 years ago in 2002.

Today, it's estimated that a quarter of a million bats are killed by cats every year, and for the bats that survive encounters with cats, many end up in wildlife rescue centres.

Dawood Qureshi, a researcher at the ´óÏó´«Ã½ Natural History Unit, said: "It's a bit controversial, but I do think you should keep cats inside.

"I don't really think that they're very useful for our environment and our wildlife.

"I know it's a bit hard because they are everywhere, a lot of the time [they are] hunting for fun.

"They're killing off bird life," they added.

Speaking alongside the conservationists at the Cheltenham Science Festival, Stefan Gates, author of a book called 'Catology' said: "There's a big debate going on about whether or not cats are good or bad for the environment, because they kill a lot of birds.

"But they also kill a lot of rats, and rats are the main species that predates on birds."

The RSPCA recommends restricting outdoor access for cats at sunrise and sunset, when wildlife is most active.

Conservationists also say that for cats that do go outside bird safe collars and bells that alert wildlife to their presence can also help.