It is feared two striped dolphins washed up near Fowey could have died from disease.
Experts from the Cornwall Wildlife Trust found pox marks on the creatures' skin.
They had a call from local residents in Fowey, who had found the first dolphin stranded alive on the beach at Coombe Haven.
The local residents attempted to assist the dolphin by putting it back in the sea, but sadly it stranded again and died before rescuers could reach the spot.
Recorder Faye Archell found a number of lesions on the dolphin's body, including deep rake (teeth) marks, inflicted by a bottlenose dolphin: "This has become a common, if surprising, sight in Cornwall in stranded cetaceans and just shows how aggressive bottlenose dolphins can be towards their own and other species. Other lesions in the skin were colonised by tiny long whale lice; fascinating creatures only 5mm in size that live out their lives on dolphins and whales by hanging on with their enormous hooked claws. Pox marks were also seen on the skin, suggesting the possibility of underlying disease, together with a possible rope mark on the tail fluke".
At the same time, the Marine Strandings Network took another from members of the public about a second animal they had seen on Polridmouth beach, about a kilometre away. Vet Katie Lewis went to search along the coast: "I examined it and saw that this dolphin also had a broken beak and some possible net marks on the dorsal fin. Other than that, there were no indications as to why it died, although it wasn't in a very good nutritional state".
Experts say for two dolphins of this relatively rare species to wash up together in the same area, at the same time and yet not be in the same condition, is highly unusual.
Marine Strandings' Network Co-ordinator Jan Loveridge says, "The explanation could be that, as both dolphins were malnourished, they may have been diseased and that can lead to them behaving abnormally. This could also increase their vulnerability to bottlenose dolphin attack, as has been suggested from previous post-mortem examinations. One could speculate that the female dolphin was staying close to its companion, which had already died, and it then stranded in the bad weather after coming too close to shore. It could have also been attacked by bottlenose dolphins".
We are being urged to keep reporting live strandings to the British Divers Marine Life Rescue on 01825 765546 and dead strandings to the MSN on 0845 201 2626.