The deaths of more than 50 whales after they became stranded on a beach in Scotland was likely caused by one of their female members suffering a difficult birth, a report has found.
Experts from the Scottish government’s Marine Directorate reported that the group of pilot-finned whales, who are a highly social species, had likely followed the female into shallow waters on the Isle of Lewis while she was in distress.
The investigation found that animals had been in good health overall prior to their deaths at the time of the incident in July 2023, with no underlying diseases or viral infections identified.
The first report was made at around 7am to Police Scotland from a member of the public, who had discovered the mass stranding on Traigh Mhor. Upon arriving at the scene, the British Divers Marine Life Rescue (BDLMR) confirmed 15 of the animals were still alive, but the response was hampered by the remote location, poor mobile phone communication and bad weather.
Only one of the 55 animals was successfully refloated and the remainder either died or were euthanised on welfare grounds.
It had initially been believed that the incident could have been caused by a disease or an acoustic disturbance from an industrially generated noise.
However a post-mortem examination of the female whale found that she had been experiencing a prolonged and difficult birth, with the report concluding: “Strong social cohesion may have then led the entire group to follow the distressed individual into shallow waters.
“Once stranded, the animals were unable to refloat themselves due to a combination of surf generated by onshore winds and the soft sand substrate on the beach.
“Drowning was determined as the primary cause of mortality for many of the stranded animals.”
The findings of the report will help towards understanding the causes behind a second mass stranding of a further 77 animals of the same species which occurred almost a year later on Sanday beach in Orkney.
Among them were two calves aged two or three weeks old, and at least one of the females was found to be pregnant.
That incident remains under investigation, with a report due at a later date.
