A quarter of native mammals now at risk of extinction in the UK, reports BBC.
This is according to the first Red List of UK mammals - a comprehensive review of the status of species, including wildcats, red squirrels and hedgehogs.
The report's authors are calling for urgent action to prevent their loss.
Prof Fiona Mathews from the Mammal Society told BBC News: "What this is clearly saying is that we have to act now - we can't continue on this same trajectory."
It is the official list categorising species based on their conservation status - or how threatened they are. Compiled after a review of all the available evidence on mammal populations, threats to their survival and to their habitats, the list has to meet the internationally-agreed criteria for assessing the conservation status of different species.
"When we draw all the evidence together - about population size and how isolated and fragmented those populations are - we come up with this list of 11 of our 47 native species being threatened imminently," explained Prof Mathews. "And there are more species that are categorised as 'near threatened'.
"That means that we need to keep an eye on these species, because while we don't yet have a red flag waving, they're still abundant enough to be able to turn things around."
The Scottish wildcat and the greater mouse-eared bat are both listed in the most severely threatened category of Critically Endangered. And much more familiar animals - the red squirrel and the water vole - have been put in the second most urgent category of Endangered.