A group of 26 common dolphins (Delphinus delphis ) have been stranded in the River Percuil near Falmouth in Cornwall.
Despite the efforts of local lifeboat crew and wildlife volunteers, the marooned dolphins have not survived.
Zoologists from the Natural History Museum's National Whale Stranding Scheme are working with veterinarians from the Zoological Society of London, to uncover more about the mass stranding.
'Whales and dolphins strand themselves for a number of reasons and we're not sure yet what happened with these dolphins,' says Liz Evans-Jones, Museum zoologist.
Common reasons for strandings are sickness, disorientation, natural mortality, extreme weather conditions or injury. Bycatch, where animals are accidentally caught in fishing nets, is now one of the main causes of death
Two or more dead animals of the same species to strand in the same place are classed as a mass stranding.
The largest ever recorded stranding was in 1927 when 150 false killer whales stranded off Sutherland in Scotland. The last UK stranding was in 1985 when 33 long finned pilot whales stranded off Humberside.
The largest mass stranding ever recorded in Cornwall was 50 long-finned pilot whale that were reported off the coast of Penzance in 1911. However in November 2001, 16 dead common dolphins were spotted floating out at sea just off Looe.
'For a number of reasons, it was concluded these were probably victims of bycatch' says Evans-Jones.
'In the past, with the help of The Cornwall Wildlife Trust, we've recorded harbour porpoises, white-sided dolphins, common dolphins and also whales beached along the Cornish coast.'
The Museum records all UK marine strandings in its national stranding database and it is part of the Defra-funded UK Cetacean Strandings Investigation Project (UKCSIP).
'Since 1913, the Museum has recorded 25 species of cetaceans in UK waters,' adds Evans-Jones, 'although we're still learning about their seasonal movements.'
Anyone finding a dead cetacean should report it immediately to the National Whale Strandings Scheme Hotline on 020 7942 5155. You should include where the animal was found, its condition, approximate length, what species you think it is and a if possible take a photo.
Whales, dolphins and porpoises belong to the animal group called cetaceans. They are mammals and they breathe air. Although they are well-adapted to aquatic life, they need to inhale air at the water's surface to survive.
Whales and dolphins can use their brains in clever ways - while one side of their brain sleeps, the other stays vigilant and keeps the animal breathing.
A dolphin's hearing is quite impressive too. They can hear above 100,000 hertz in frequency, which is over 6 times higher than humans and even higher than dogs.