Quad bikes damage to the Munro Ben Wyvis near Garve
Land on one of Scotland's highest mountains has been damaged by the illegal use of off-road machines, such as quad bikes.
Scottish Natural Heritage and Police Scotland said Ben Wyvis near Garve, north of Dingwall, was a protected site of special scientific interest.
Ben Wyvis, from the Gaelic "Beinn-Uais", meaning "awesome mountain", has important plant and animal habitats.
Its birds include dotterel, a globally threatened migratory species.
SNH and police said the illegal use of off-road vehicles has also been found at another protected Highlands site, Loch Fleet near Golspie.
While it has been an ongoing issue, SNH and police said there was "a spike" last month in damage caused by quad bikes, motorbikes and motorised karts to Ben Wyvis, a Munro of 1,046m (3,431ft) metres, and sand dunes at Loch Fleet.
Police Scotland wildlife crime officer Dan Sutherland said: "The use of off-road vehicles on protected sites such as Loch Fleet and Ben Wyvis is not only damaging to habitats and wildlife, but may also pose a hazard to members of the public who are responsibly accessing these sites for recreation.
"The use of motorised vehicles on any land without permission is an offence, and other offences may be committed against wildlife legislation."
Loch Fleet National Nature Reserve manager Adam Rose said there had been "a spate of damage" caused by quad bikes, motorbikes and off-road karts in recent months.
He said: "Sand dune habitats are sensitive to damage from vehicle use and damaged areas can take a long time to recover, particularly where the sand and soil are exposed to the elements.
"Large ruts, doughnuts and long skid-marks, as we have had recently Loch Fleet, are particularly damaging as they take longer to restore.
"Of course, this takes even longer where there has been repeated damage to one area. As well as the physical damage to the site, internationally important populations of birds that overwinter at Loch Fleet may be disturbed."