Red squirrels are being released into a Highland forest as part of wider plans to "kick-start" their reintroduction to north-east Scotland.

The conservation charities Trees For Life and Woodland Trust Scotland announced on Thursday they are releasing around 20 red squirrels to a Sutherland wood.

The animals will be released throughout October and November at the Woodland Trust Scotland's Ledmore and Migdale Woods near the village of Spinningdale on the shore of Dornoch Firth.

The first animals were released last week at what is the most northern reintroduction site to date in the Trees For Life red squirrel reintroduction project, the charities said.

Trees For Life's red squirrel project manager Becky Priestley said the squirrels - which will be taken from the existing populations in Inverness-shire and Moray - will be able to spread safe from threats from grey squirrels.

She added: "We are reintroducing red squirrels to carefully chosen native woodlands where these iconic wild animals belong, but from which they have been lost.

"The Woodland Trust's Ledmore and Migdale Woods are a perfect habitat for red squirrels.

"It's fantastic to be helping the species return to this beautiful part of the Highlands, and to be kick-starting their reintroduction to north-east Scotland."

The organisations said that because red squirrels travel between trees and avoid crossing large open spaces, they cannot return to now-isolated woodlands on their own.

The squirrels will be transported in hay-lined nest boxes which are fixed to trees and have grass-filled exit holes allowing the squirrels to leave when ready, the charities said.

Food is provided for several months as the squirrels get used to their new habitat.

The charities said there are only an estimated 138,000 red squirrels surviving in the UK, including around 120,000 in Scotland.

Numbers of the mammals have been decimated by reduction of their forest homes to isolated fragments and by competition and lethal disease from non-native grey squirrels, they added.

Ross Watson, North Scotland site manager at Woodland Trust Scotland, said: "We're delighted to be involved in Trees For Life's inspiring and much-needed red squirrel reintroduction project.

"The ancient woods at Ledmore and Migdale include a stunning pinewood and one of the most northerly oak woods in Britain. It is perfect for red squirrels."

New populations of red squirrels already established by Trees For Life - following the charity's reintroduction of 140 animals across several Highland locations between 2016 and 2018 - have been successfully breeding and spreading into wider areas, they said.

Next spring Trees For Life plans to extend the red squirrels' range further west by releasing another 30 animals in the Morvern peninsula.