Ministers have launched a campaign to save the red squirrel from extinction in Scotland.
Scotland's red squirrel population is under threat from 'rats with tails'
Deputy Environment Minister Rhona Brankin has urged the public to report the squirrels' whereabouts as part of an "action plan".
Scotland's 120,000-strong native population has been under threat from non-native grey squirrels and from the deadly squirrel pox which they carry.
Ms Brankin has also called for a conference to discuss the problem.
Experts due to attend the Edinburgh conference next month have been urged to produce a survival plan for the creatures.
The minister has appealed to the public to help Scottish Natural Heritage with the Scottish Squirrel Survey.
"The red squirrel is under serious threat in Scotland and we need to maximise our knowledge of our populations in order to halt the decline of this native species," she said.
"We are committed to protecting the red squirrel. We are working with SNH to bring experts to Scotland next month for a landmark conference on red squirrel conservation."
Survey spokesman Dr Mel Tonkin said: "The urgency to find out exactly where the most vulnerable populations of red squirrels are to be found, as well as where the safest populations are, cannot be over-stressed.
"At the same time we need to know the limits of where grey squirrels have spread to because, as carriers of the deadly red squirrel pox virus and as efficient competitors for scarce natural squirrel food supplies, the alien grey squirrel poses the chief threat to red squirrels.
The grey squirrel poses the biggest threat to the red variety
"We hope that by the end of 2010 we will have covered all the crucial places in Scotland and will have started to put in place measures to secure all saveable populations of red squirrels. We also hope to prevent the further spread of grey squirrels."
Grey squirrels were introduced to Britain from America in the 1800s.
They digest acorns and large seeds more efficiently than the more delicate native red squirrel and have spread to most of central Scotland, forcing out the indigenous species.
Squirrel pox was found last summer by the Moredun Research Institute near Edinburgh in grey squirrels coming across the border from Cumbria.
A spokesman for the European Squirrel Initiative urged people to report any sightings of sick or dead red squirrels.
The infection has little effect on the grey squirrel but it causes a myxomatosis-type illness in the dwindling red squirrel population.