Long-eared bats have halted a planning application for a #163;400,000 all-weather sports pitch at a school.
Ecologists say the floodlighting from the pitch, planned for Orton Longueville School in Peterborough, Cambridgeshire, could disturb the animals in nearby woodland.
A new survey will now have to be carried out to find out how the lights will affect the bats.
Campaigners battling to stop the floodlit sport pitch being built near their homes have cautiously welcomed the news.
They are hoping the Peterborough City Council will rethink its plans because of their concerns about their homes being affected by noise from the pitch.
Resident Celia Ireland, 68, said: "I'm not confident they will find in our favour.
"We were hoping they would consider moving the pitch because of the noise. We have had a lot of support from people living around Peterborough, so we hope they will do it not just for the animals, but for the residents, too." ib.