Gas engineers were told to 'pipe down' after a roost of unusual bats was found under the road on which they were working.

Surprised workers for Transco, the gas pipeline operator, discovered them while carrying out emergency repairs on a broken pipe at Otley Bridge, Otley.

The team, which began the work on August 13, had to consult town members of the West Yorkshire Bat Group who advised them to avoid making too much noise above the bats' home.

The colony of Daubenton's bats, a special species which feeds by swooping down on to the river's surface to scoop up insects, has lived over the River Wharfe for about eight years.

Bob Harrison, Transco's network assistant responsible for the project, said the team took every precaution to protect the colony of bats which lives under the bridge arches.

"It wasn't until very late on that we discovered the bridge was home to a roost of Daubenton's bats," he said.

"At that point we did everything possible to ensure our essential emergency works did not interfere with the colony, by consulting with the West Yorkshire Bat Group.

"Protecting the Daubenton's made the job even more difficult, especially as the gas main is encased in concrete and needed some intricate excavation work, which is all a credit to the Transco team."

John Popplewell, a member of the West Yorkshire Bat Group and co-ordinator of walks for the Bat Conservation Trust, said the group visited the site and was concerned the work would frighten the bats, which number up to 70.

"The colony has been there for a very long time and, although they do go away at certain times for various reasons such as breeding, we were worried if the bats were disturbed they would not return," he said. "But the work was done without them being affected and we're all very pleased."