Adventurous people are wanted for the red squirrel search
A project dubbed extreme squirreling is to seek out red squirrels in parts of the Highlands where few, or no, records of the mammals exist.
Conservationists at See Red Highland said Forestry Commission Scotland held statistics for numbers in "core areas".
But they said little was known about populations in Sutherland, Caithness, Wester Ross, Morven and Ardnamurchan.
Events will be held where volunteers will search for reds, or evidence of them such as eaten pine cones.
More information on numbers will also be sought from Lochalsh and the south-western part of Badenoch and Strathspey.
Juliet Robinson, of See Red Highland, said the effort would help guide planning on protecting habitat against the non-native grey squirrel.
The larger mammal competes with the native species for food and carries a disease that is fatal to reds.
Sightings of greys have been reported in the Highlands, but none have been caught.
Recorders and surveyors have gathered information on reds in their stronghold areas.
Ms Robinson said: "All of this forms a vital part of finding out where red squirrels are living and this helps plan for the day that populations of grey squirrels might come into Highland.
"Fortunately this has not happened yet, and this is largely thanks to our dedicated red squirrel enthusiasts.
"Now we want to target areas of woodland outside the core red squirrel habitats."
She added: "This is for adventurous people of any ages. It requires you to bring out the detective in you, and it shouldn't put you out of pocket as we may be able to pay mileage.
"You will be armed with maps and guides to finding red squirrels - guides to 'squirrelled' cones and nuts, dreys and advice on when you are most likely to encounter a red squirrel."
The project - which has been launched during Red Squirrel Week - has received European Union funding.
Events for schoolchildren will be held later this week at Nethybridge, Craig Phadraig in Inverness-shire and Ardnamurchan.
Grey squirrels are seen as a threat to native reds
The Highlands of Scotland are today considered by conservationists and the government as one of the last great strongholds for red squirrels.
But for 43 years, from 1903, there was an active effort on estates across the Highlands to trap, shoot and kill reds.
By 1946, the Highland Squirrel Club had killed 102,900 squirrels and paid out £1,504 in bounties.
Tails were submitted as proof of kills.
Reds were extinct, or on the brink of extinction, in the Highlands by the 1800s because of a loss of woodland habitat.
In 1844, Lady Lovat of Beaufort Estate near Beauly, succeeded in getting the government to re-introduce the squirrels to the Highlands.
By the 1900s, the squirrels had spread from the boundaries of the estates where they were released and were blamed for causing damage to Scots pine and other conifers.
The garden novelty had become a menace threatening thousands of acres of plantations.