There is strong evidence that grey seals could be responsible for fatal "corkscrew" injuries to other seals rather than boat propellers, according to the Scottish Government.
Scientists investigating seal deaths said they observed a grey seal killing five young seals, leaving them with the distinctive spiral wounds.
The team said this finding, combined with recent similar evidence from Germany, suggests such behaviour may be more common and could explain the unusual clusters of injured seals found in Scottish waters.
The injury is described as a single, smooth-edged cut starting at the head and spiralling around the body.
The Sea Mammal Research Unit at St Andrews University was commissioned by Marine Scotland to investigate after 86 seal carcasses were found between 2009 and October last year with the distinctive spiral markings.
The investigation previously suggested certain types of boat propellers could be responsible.
A number of grey seals in the Firth of Forth were tagged to examine potential interactions with shipping and discover if any suffered the spiral injuries.
During this work a number of examples of young grey seals with the injuries were found but these were recorded to be the result of predatory behaviour by adult seals.
However, they said the evidence does not completely eliminate ship propellers but it is now less likely they are a key factor.
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."
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