Tidier gardens and urbanisation have led to a decline in the number of hedgehogs in the UK, a survey says.
Hedgehog decline was greatest in western regions
Development of parks and gardens have contributed to a 50% decline in some areas, the HogWatch survey suggests.
Nearly 20,000 people took part in the two-year survey, making it one of the largest of its kind, organisers said.
The survey was carried out by the University of London for the People's Trust for Endangered Species and the British Hedgehog Preservation Society.
The data gathered by the volunteers allowed the research team to develop a better understanding of the small mammals' nationwide distribution.
They said that the study revealed an east/west divide, with more hedgehogs spotted in eastern regions.
Commenting on the findings, study co-ordinator Paul Bright from Royal Holloway, University of London, said: "Increasing urbanisation and tidier gardens are pushing hedgehogs out from the places where most of us live.
"In the wider countryside, landscapes that have smaller fields appear better for hedgehogs," Dr Bright added.
As well as development in urban areas, an increase in the number of badgers (which eat hegehogs) has been linked to the decline.
However, Hugh Warwick of the British Hedgehog Preservation Society said the jury was still out on that hypothesis.
"Hedgehogs and badgers have co-existed for millenia, and still live side-by-side... and where the decline in hedgehogs is highest, there are fewer badgers," he said.
"It seems likely that the way we have altered the environment is at the heart of the problem."
The team said the two-year project had provided them with possibly the largest distribution dataset for a single species over a short period of time.
Dr Bright and his team plan to use the results to compare current hedgehog distribution in Greater London with data from the 1960s.