Endangered red squirrel populations have plummeted from about 3.5 million to less than 300,000 in the UK, with their grey-haired rivals continuing to thrive.
In England, the situation is dire for reds.
The Woodland Trust reckons there are only 39,000 of them left, while the Save Our Reds campaign thinks just 15,000 remain, including in conservation areas such as Formby on Merseyside.
In May the group said that red squirrels, which "still cling on" in parts of northern England, could disappear within 25 years.
In contrast, since their introduction from North America in the 19th Century, greys have thrived at the expense of their distant cousins, which compete for habitats and carry lethal viruses.
The first verifiable importation of greys, external is widely understood to have come 150 years ago, when a Victorian banker named Thomas V. Brocklehurst is said to have released a pair of greys into Henbury Park, near Macclesfield in Cheshire, that he had brought back from a business trip to the United States.
According to Graham Paskett from the Red Squirrel Survival Trust, there are now between 2.5 million and 2.7 million greys in the UK.
Jackie Foott, from the British Red Squirrel conservation group, told the BBC that reds and greys cannot coexist in the same place and that to protect the reds you have to "get rid of the greys - we realised that a while ago".
In May, a spokesperson for the Department for Environment, Food and Rural Affairs said the government was protecting endangered red squirrels by tackling the threat of non-native grey squirrels.