Several hedgehogs have been killed after a property developer used tractors to clear ground where they undefended to build housing, according to campaigners.
An investigation is underway after the animals were found dead on land in Benllech on the isle of Anglesey.
The field, which was said by locals to have contained "an abundance of wildlife" is being developed into a housing estate by developers ClwydAlyn.
The housing association claims that "all work is being carried out in partnership with qualified ecologists".
But after heavy machinery was used to treat the field, a number of hedgehogs have reportedly been found dead.
People living on the nearby Pont Y Briallu estate claim the developers and Isle of Anglesey County Council did not take adequate steps to protect the wildlife living on the site.
Catharine Roberts told North Wales Live that she was "absolutely fuming" when she saw that the work was being carried out.
"Rather than cutting it by hand, as they should have, to protect the abundance of wildlife in the field, they came in with a massive tractor which mangled up the hedgehogs as predicted."
Jane Evans, who also lives on Pont Y Briallu, described the incident as "horrifying".
She added: "Anybody interested in the wildlife would have cut it by hand first before ploughing through it with a tractor."
Craig Sparrow, Executive Director of ClwydAlyn, said: "ClwydAlyn was granted planning permission to develop 27 homes on this site in Benllech to provide much-needed affordable homes for local people, in partnership with the Welsh Government and Anglesey County Council."
He added: "In accordance with planning conditions, we have started pre-construction works to clear vegetation and enable an archaeological dig to take place prior to construction. All work is being carried out in partnership with qualified ecologists."
An Isle of Anglesey County Council spokesperson said: "Our Planning Service is currently looking into this matter after receiving a number of complaints from local residents."
A spokesperson for RSPCA Cymru said: "We're very sorry to hear reports that a number of wild animals were allegedly killed during developments at this housing estate.
"The presence of an ecologist is always an important and welcome step in advising on mitigation measures required for a development, based on surveying local wildlife.
"Mitigation for such developments is usually to erect fencing and then to check the area for protected animals prior to clearing the site."
"The RSPCA always recommends checking an area - whether a large field or small garden, for animals prior to carrying out any work.
"We continue to call for animal welfare to be a material consideration in the planning process, and urge developers to plan carefully to minimise or eliminate welfare risks when carrying out work."