Risso’s dolphins in the Sound of Eriskay

On Thursday, 11th August three dolphins were observed swimming around on the east side of Eriskay causeway, near the bridge. One very much smaller than the others stayed close beside one of them, so almost certainly a mother and calf.

There was some discussion initially about the species; only brief views of parts of the head and back were visible when they took breaths. Initial suggestions were Atlantic white-sided dolphin; or possibly Bottlenose dolphin; but eventually close scrutiny of some good photographs and video sequences led to the conclusion that they were Risso’s dolphins (Grampus griseus). Some photographs showed pale parallel lines on the sides of the calf, the remains of ‘foetal folds’ resulting from it having been curled up inside the mother; evidence that it was probably no more than a few weeks old. Apparently Risso’s dolphins have been seen on a number of occasions on the east side of Uist recently.

There was concern that they might strand as although there is a deep channel from west to east, at low tide much of the sound is very shallow and large areas dry out, especially at spring tides as we had just then. The two larger ones did indeed become grounded in shallow water after midday on Friday, but by 2pm the rising tide refloated them to swim freely. There were no further reports of their stranding.
British Marine Divers Life Rescue (BMDLR) were alerted to the situation, and although they have no trained volunteers in Uist, could have helped if necessary. They passed the news on to the Scottish Marine Animal Strandings Scheme (SMASS), which also kept in touch with local volunteers.
The three animals stayed on the east side of the causeway, showing no inclination to pass through to the west, though at times they were close to the bridge. They also went over towards Sgeir an Fhèidh, and latterly further away towards the open waters of the Minch.

Generally’ they seemed to be swimming about quite calmly, showing no signs of distress, with only the upper parts of the head and back visible as they rose to breathe. The single animal was observed ‘spy hopping’ occasionally and also vigorously tail slapping.

By the morning of Wednesday 17th our visitors had departed.

News had got around quickly and over their few days’ stay, the dolphins attracted a lot of attention from residents and passing summer visitors, who gathered on the causeway to watch them, hoping they would be all right.

Many people contributed to this note, not least Chris Brooks, Peter Keiller and Donald Iain Campbell, who had very helpful observations, photographs and video sequences, Mariel ten Doeschate of SMASS for discussion of the species and age of the calf, Dan Jarvis of BMDLR, Mary Margaret Morrison, who saw them from her bus and other residents for keeping in touch and reporting their observations, and David Steele for his observations in the Minch.

Photos by Peter Keiller and Carla Brooks