Volunteers are needed to help save red squirrels from falling victim to a fatal outbreak of squirrel pox.
Eleven red squirrels have died of the disease in Formby
The call comes after 11 red squirrels died from the disease at the National Trust reserve in Formby, Merseyside.
The disease is carried by grey squirrels, who are not affected by it, but experts fear the reds could be wiped out if it is not contained.
Lancashire Wildlife Trust is appealing for people to help spot any of the creatures which show signs of sickness.
Volunteers can help by contacting the trust and taking part in an organised search for sick red squirrels.
If removed, they can be prevented from spreading the infection. Otherwise, the pox could spread through the whole colony.
Fiona Whitfield from the trust said: "We are in a desperate situation. Anyone who can spare the time to take part in a regular sweep of the National Trust site should call me straight away.
"If we don't win this battle, we could be saying goodbye to our red squirrels forever."
Members of the public are strongly advised not to handle sick squirrels without the necessary training and protective equipment.