Rare lesser horseshoe bats are gradually making a re-appearance in Oxfordshire after being virtually absent for decades.

At one time, this species of bats was common across England, but it retreated to Wales and the West Country as habitats and sources of food declined due to old buildings being demolished or converted into houses or offices and changes in farming practices that saw many hedgerows uprooted to create larger fields.

Wildlife researchers and bat groups have begun finding evidence that the lesser horseshoes are moving eastwards and colonies have been discovered in the Welsh Marches, counties such as Shropshire and also in Gloucestershire and Wiltshire.

And lesser horseshoes have been seen by members of the Oxfordshire Bat Group further east in a variety of locations around the Chipping Norton area.

“We have known of two small colonies in disused railway tunnels for some time,” said Reg Tipping, a group member.

More recently, when members were carrying out a bat survey of buildings, the householder said: “What about the bat house?”

Mr Tipping said: “We thought what bat house? We had never heard of it. So we were taken to the old building nearby and found several lesser horseshoes were in residence. It was an exciting find.”

Since then, members have been quietly observing the bats in the spring and early summer to assess whether the colony was a summer or maternity roost.

A maternity roost is made up of predominantly females, although about 25 per cent could be males.

“We saw at one time that baby bats, or pups as they are known, were clinging to the adults,” said Mr Tipping.

Originally, it was thought the colony could have been a summer roost and an outpost of a larger colony over the county boundary in Gloucestershire. It was after consulting with an expert on lesser horseshoes, Henry Schofield, of the Vincent Wildlife Trust, based in Ledbury, that it was shown to be a colony in its own right.

Bat group members will keep an eye on all three groups in the Chipping Norton area, although they will be somewhat restricted as there is now no public access to the old railway tunnels for health and safety reasons.

“However, we believe these colonises show that this bat species is extending its range into Oxfordshire and we strongly suspect there are other colonies of the lesser horseshoes in that part of the county and possibly elsewhere,” said Mr Tipping.

There has also been a report of lesser horseshoes in Buckinghamshire, but the sighting has yet to be verified.

Over the course of a year, lesser horseshoes live in two locations.

Hibernating roosts in the winter months are often located in cool locations such as railway tunnels, where the temperature is fairly stable.

In the spring and summer, the bats like warmer sites like old buildings. The two roosts are sometimes not far apart, hence the need to differentiate between locations when a colony is found.

There are 17 species of bat in Britain and the lesser horseshoe and the greater horseshoe are among the rarest.

In the order of endangered species the greater are more at risk than the lesser horseshoes.

According to Henry Schofield, conservation programme manager for the Vincent Wildlife Trust, the greater horseshoes are restricted to the south and west of Wales and south-west England.

Lesser horseshoes declined about 50 to 60 years ago and are now found in Wales, the West Midlands, the West Country and along the south coast at least as far east as Dorset. They are also found in Ireland.

“We have been working on both lesser and greater horseshoes for some years and have set up about 40 bat reserves in Britain and Ireland for both species.

“We have tended to concentrate on the lessers in recent years because they are more widespread in England,” said Mr Schofield. The majority of lesser horseshoes are found in old buildings, usually of stone with slate roofs.

Mr Schofield said that most of these buildings were associated with old country estates and they included coach houses, churches, and even ice houses.

“We spend a lot of time enhancing the buildings, which become the reserves.

“It can sometimes mean a building is partly renovated because the lesser horseshoe, unlike some bats, cannot crawl and needs to be able to fly into a building to roost.

“This means entrances have to be modified.”

Mr Schofield attributed the previous national decline in lesser horseshoes to the loss of buildings in the countryside and the uprooting of hedges.

Lesser horseshoes feed off midges, found in hedgerows and at the edge of broadleaved woods.

They will also eat moths and crane flies.

He added: “Lesser horseshoes use their call, which is more high pitched than some other bats, to follow features of a landscape, such as hedges, to reach their food.

When he lived in North Wales he first became aware of the lesser horseshoes and has been fascinated by them ever since.

But why the name horseshoes?

“It is because of their face. They have a flap of skin around their nostrils, which we believe they use to make their call more directional, helping them to fly over the countryside and around buildings,” said Mr Schofield.

Findings of lesser horseshoes in Oxfordshire were a positive sign that the species was extending its range eastwards, he added.