Suffolk Wildlife Trust looks for hedgehog 'black holes'
People in Suffolk who have never seen a hedgehog near their home are being asked to contribute to a survey.
Since April, Suffolk Wildlife Trust has collected more than 7,250 records from people who have seen hedgehogs, dead or alive, around the county.
It now wants to focus on population "black holes", where no hedgehogs have been seen for the past two years.
Dr Simone Bullion said the negative sightings would be "valuable" in forming plans to help the species.
"The data we have will help us identify where hedgehogs are in the country, what we really need to do now is clarify where they are not," she said.
The trust said it had received about 200 records from people who had reported never seeing a hedgehog near their home, but as these were interspersed with records of live animals, they were "less reliable".
The UK hedgehog population has fallen from about 30 million in the 1950s to a million today, the trust said.
It said the response to the survey had been "fantastic" and showed "how fondly the species is regarded".
The long-term objective is to provide more "corridors" between known habitats.