The red squirrel, the wildcat, and the grey long-eared bat are all facing severe threats to their survival, according to new research, BBC reports.
They are among 12 species that have been put on the first "red list" for wild mammals in the UK.
The Mammal Society and Natural England study said almost one in five British mammals was at risk of extinction.
Factors such as climate change, loss of habitat, use of pesticides and disease are to blame, the report said.
It said the hedgehog and water vole have seen their populations decline by almost 70% over the past 20 years.
However, it is good news for the otter, pine marten, polecat and badger, which have all seen their populations and geographical range spread.
The report is described as the first comprehensive review of the population of British mammals for 20 years.