There's been a big drop in the number of hedgehogs in Britain.
Two wildlife charities say their population has fallen by a quarter over the past 10 years.
They're asking people to make their gardens more hedgehog-friendly by planting hedges and leaving leafy areas where they can shelter.
There's going to be new research over the next three years to get a better idea of why hedgehog numbers are going down and what can be done about it.
It's thought that the prickly mammals have suffered because lots of hedgerows and grassland where they live have been destroyed, and because of farmers using pesticides which kill the insects that they eat.
The study was carried out by the British Hedgehog Preservation Society and the British Trust for Ornithology.