Injuries found on dead seals once blamed on ship propellers are probably caused by other seals.
Between 2009-2014, 86 seal carcasses were found in Scotland with unusual spiral injuries, the cause of which was then unknown.
Strong evidence has been uncovered showing that the predatory behaviour of grey seals – sometimes involving cannibalism – is likely the main cause of so-called spiral seal deaths, often referred to as “corkscrew seals”.
Staff at the Sea Mammal Research Unit, at St Andrews University, observed an adult grey seal killing and partially eating five young seal pups, leaving them with the distinctive spiral-shaped injuries.
Combined with recent evidence from Germany, this suggests that such predatory behaviour may be more common than thought, and could explain unusual clusters of injured seals found in Scottish waters.
The Scottish Government said the evidence does not completely exonerate ship propellers, but they are now less likely a key factor in corkscrew injuries.
Environment Secretary Richard Lochhead said: “The clusters of corkscrew seal deaths were unusual and worrying. In common with many of the creatures that live in our seas, seals are animals that are loved by the public.
“It is very important that we understand what caused these unusual deaths and we now have important evidence that natural predatory behaviour is likely to be the main cause, rather than ship propeller injuries as we first thought. This provides some reassurance for the shipping industry .
“This information will help to inform regulators, developers and others enabling them to take it into account in their activities.
“Marine Scotland will continue to monitor our seal population for further injuries and any evidence about the causes.”