Pilot whale's difficult birth may have triggered mass stranding

A large-scale stranding of long-finned pilot whales in Lewis may have been triggered by a female experiencing a difficult birth, according to a new report.

More than 50 whales died after they got into difficulty in Tolsta Bay in July 2023.

Experts said the pod's "strong social cohesion" may have led the group to follow the distressed female into shallow waters.

The Scottish Marine Animal Stranding Scheme (SMASS) said its investigation found the animals to have been in good overall health.

Members of British Divers Marine Life Rescue and other volunteers attempted to save some of the pilot whales.

In its report, SMASS said it found that a mature female had experienced a difficult birth.

The scientists said this suggested a "possible social trigger for the stranding".

They added: "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."

Long-finned pilot whales are large dolphins and described by Whale and Dolphin Conservation as having "incredibly strong bonds".