Boats will be used to herd whales from a Scottish loch into the open sea ahead of a huge military exercise in the region.
Experts have been monitoring the northern bottlenose whales in Gare Loch in Argyll for the last month.
They want to move them from the sea loch because sonar used by warships during the Joint Warrior military exercise could distress the animals.
There are also concerns that one of the whales is looking “skinny”.
Europe’s largest military exercise begins on Saturday and its headquarters will be at Faslane, the naval base next to Gare Loch.
The operation to move the mammals will be led by the British Divers Marine Life Rescue (BDMLR).
It said five whales have been spotted in the Loch Long area and some have entered some of the smaller lochs nearby.
“It is very unusual for them to be in coastal waters, however we have had similar incidents in recent years where animals of the same species have entered lochs, including Loch Long, that have subsequently left of their own accord without intervention, and presumably have succeeded in returning to their proper habitat,” a charity spokesman said.
“We recently became aware that a significant military exercise is due to begin next week, and as whales are particularly sensitive to underwater sound, have been concerned about the effect it may have on the animals.”
It added that attempting to move them “of course does come with risks of its own and there is no guarantee it will be successful given the depth of water and distance that needs to be covered, so will be undertaken with as much care as possible.
“We will of course reassess our actions and options if the whales decide that they will not go.”
Gavin Lemon, a volunteer with the charity, said the animals will be herded from Gare Loch using a number of boats in formation.
He said it was important to move the animals while they were healthy and in good condition.
“We’ve been monitoring them – they are feeding on local fish,” he said. “They usually like squid and the like, diving up to 1,000m (3,000ft).
“Gare Loch is about 25m (80ft) deep. So they’ve not been having their normal diet, but it has been sustaining them.
“However, one of them looks skinny which is not a good sign with a whale.”
Jamie Munro has been photographing the whales while they have been in the area between the naval base and the top of the loch.
He told BBC Scotland: “At first we thought it a real novelty with the three of them tail slapping and breaching. We thought they were fishing.”
But he said concern grew and whale watchers have expressed concern that the animals were in distress.
“I’ve been watching them now from our house for six days and every morning I go out early hoping not to see them and that they have made it out, but sure enough they pop up and so it goes.”
Warships, aircraft, marines and troops from the UK, Nato and allied forces will take part in the military exercise, which is due to run until 15 October.
A spokesman for the Ministry of Defence said: “The Royal Navy takes its environmental responsibilities very seriously and continues to work with the relevant UK authorities to ensure all practical measures required to reduce environmental risk and comply with legislation are taken.
“A necessary series of safety checks is observed and an environmental risk assessment is carried out before any underwater task is undertaken by MoD, to minimise any potential risk to marine life.”
He added that members of the armed forces who are involved in the Exercise Joint Warrior training in the area will be made aware of the presence of the whales and the latest sightings.
“All participants are aware that environmental protection remains a priority for the exercise and we are prepared to amend the programme if these whales remain in an atypical situation,” he added.
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