Media playback is unsupported on your device Media caption BBC science reporter Victoria Gill goes in search of the grey long-eared bat at a secret location in Devon

One of the UK's rarest mammals, the grey long-eared bat is in danger of disappearing from the country, according to research.

A four-year study by scientists from the University of Bristol estimated there were 1,000 of the bats left - all confined to southern England.

The researchers are calling for the bats' foraging habitat to be protected.

The Bat Conservation Trust has published the findings in a new conservation management plan.

Dr Orly Razgour, who led the research, said that very little was known about the species before she started her study.

The UK's grey long-eared bats need greater conservation efforts before we lose them Dr Orly Razgour, Lead researcher

"We thought there might be more colonies, that it might be less rare than we suspected," she told BBC News.

"But after studying the species for four years, we realised that they are very rare.

"We also know that [it has] declined dramatically in the last century.

"We know of three maternity colonies [colonies where the female bats give birth and raise their young] that have disappeared in the past few decades."

Although the UK's grey long-eared bats have always been confined to the relatively warm south of England, they have now been squeezed into just a few fragmented colonies.

The bats are confined to small pockets along the south coast of England, including the Isle of Wight, with a small number found in the Channel Islands and a single one recorded in South Wales.

It is so rare, in fact, that BBC News was asked to keep the exact location of the colony we visited in Devon a secret, to avoid the bats being unnecessarily disturbed.

Image caption The grey long-eared bats are confined to small pockets along the south coast of England

Dr Razgour explained that the decline was linked to the "dramatic decline of lowland meadows and marshlands, the bat's main foraging habitats".

"The long-term survival of the grey long-eared bat UK population is closely linked to the conservation of these lowland meadows and marshland habitats," she said.

The Bat Conservation Trust is calling on influential groups, including land owners, conservation organisations and Natural England, the government adviser on the natural environment, to manage the landscape around roosts.

Bat facts There are over 1,100 species of bats in the world and just 18 species in the UK

All UK bat species use echolocation - emitting sounds and listening to their echoes - to navigate and hunt for insects in the dark

A tiny pipistrelle, which weighs just a few grams can eat up to 3,000 insects in a night. This means that bats play an important role in controlling agricultural pests. Source: Bat Conservation Trust Watch: The secret behind bats' amazing agility

They have also stressed the importance of managing the land between known roosts, so the remaining colonies are connected and the bats are able to breed.

In a statement, Natural England endorsed the conclusion that the grey long-eared bat's habitat had been "greatly altered throughout the last century through changes in farming practices and land management techniques".

It added: "[Bats] are amongst the most protected mammals in Britain; this degree of protection recognises the level of threat posed to these species and seeks to conserve populations for this and future generations."

But Dr Razgour told the BBC, that although bat roosts were protected by law, bat foraging and commuting habitats are not.

"As [our management plan] shows, loss of foraging habitats is a major threat to the long-term survival of grey long-eared bats in the UK."

The Bat Conservation Trust says the grey long-eared bat should be afforded "UK Priority Species status" by the statutory bodies Natural England, the Department for the Environment Food and Rural Affairs and the Joint Nature Conservation Committee, to ensure that more funds are directed towards protecting its habitat.

Dr Razgour: "The UK's grey long-eared bats need greater conservation efforts before we lose them"