Media playback is unsupported on your device Media caption Rescue team leader Alasdair Jack says some of the whales have serious head injuries

Marine animal experts are preparing for a potential mass stranding of more than 60 pilot whales in South Uist in the Western Isles.

The whales were spotted in Loch Carnan on Thursday afternoon and about 20 were said to have cuts to their heads.

It is thought the injuries may have been caused by the whales' attempts to strand themselves on the rocky foreshore of the sea loch.

However, animal welfare experts think they may not be in imminent danger.

Dave Jarvis, from the British Divers Marine Life Rescue (BDMLR), who is at the scene, said low tide had come and gone and the whales had remained out at sea.

He said: "They are not in imminent danger of stranding.

"We are just keeping an eye on them and see what they do next. We are trying to make sure they don't become distressed."

Analysis There are two species of pilot whale, and together they are found just about everywhere in the world's oceans. They dive to hunt squid and fish, and live in social groups numbering up to 100 individuals that are mainly nomadic. The social bonds within these groups appear to be strong, and it may be this that makes strandings relatively common. Last year saw a mass stranding on the Donegal coast, as well as a number in New Zealand. If one individual gets in difficulties in shallow waters, the others remain with it. Pilot whales depend on sound for hunting and communication; and with many individuals crowded into a shallow bay, they may become confused and disoriented by the sheer amount of calls. Although strandings are traumatic, both species of pilot whale are abundant.

Sick and injured whales are known to beach themselves to die.

However, at times, dying whales have been followed to shore by healthy animals.

Conservationists have also suggested the whales may have got lost, or entered the loch following prey.

Rescuers said inflatable pontoons for refloating whales were on the way.

The pod had been moving back and forth from the shore and rescuers said the animals were "very vocal", which may be a sign of distress.

The whales, a deep water species, have moved from the loch back to a nearby bay, where they were seen earlier on Thursday.

Members of the BDMLR have been at the scene to try and save the animals.

Scottish organiser Alasdair Jack said preventing the mammals from stranding would cause unnecessary suffering and the animals would only move on to another shoreline.

He said: "Rather than try to stop them coming ashore, we would let them come ashore and then try to deal with that situation when it arose.

"We have got several sets of pontoons with us, which is our whale refloatation equipment, and we have got more on the way.

"We have currently got 12 sets congregating on the Uists, which is basically every set in the UK."

He added: "We are going to let them play out whatever role they want to do and take it as it comes."

'Unsolved mysteries'

Scottish SPCA senior inspector Calum Watt said the whales' strong social bonds meant healthy animals within a pod would follow sick and injured ones on to shore.

He added: "At this stage we remain hopeful they will not strand themselves but our concern is the injured whales will come onshore and be followed by the rest of the pod.

"Attempting to refloat so many whales would be a huge task and if they do become stranded we'll need to decide upon the best course of action.

"The largest number of whales we've tried to refloat before was seven, which was in 1993. Unfortunately all seven returned to the shore and died."

Wildlife tour operator Steve Duffield, who has photographed the pod, said it was unusual to see pilot whales so close to shore.

He said: "It is a deep water species and occurs in the Minch and Sea of Hebrides, but is very rarely seen in coastal lochs.

Eyewitness The whales have moved from where they were this morning. They were further in towards shore, but seem to have moved further out to the other side of some fish farm cages on the loch. At the moment, the whales are being monitored from the shore. If they do beach, there will be a triage situation where the healthy whales will be separated from the injured ones. The injured would then be despatched - but we are some way off from that situation.

"To see the whales so close to the coast is exceptional."

Sarah Dolman, of the Whale and Dolphin Conservation Society (WDCS), said it was hoped the species would make their way back to deep water.

She said: "This group of animals may have got lost, or they may have come in following some prey.

"I hope we won't find out by them coming ashore and it will remain one of those unsolved mysteries."

In October a pod of pilot whales were in danger in the same sea loch.

Days later, 33 whales, thought to be the same group, were discovered dead on a beach in County Donegal.

Mr Watt, of the Scottish SPCA, said: "It is incredible that a second pod, this time probably more than twice the size, has arrived in the same area."

"There is no reason we know of why they would have come to the same location."

Pilot whales can grow up to about 20ft (6.1m) and are among the most common marine mammals.