The samples had previously been identified as brown bears.
Advancements in the chemical study of bones and teeth allowed researchers to re-examine the remains.
Bones of other animals now extinct in Scotland have also been recovered from the system of caves over the years – including lemming, wild horses, lynx and wolf.
Prof Kate Britton, from the University of Aberdeen, said: “We have identified several samples which stick out like a sore thumb both from the diets of other bears living in Scotland thousands of years ago and from what we’d expect of today’s brown bears.
“Instead of consuming the meat of land-based animals, plants, or even a little salmon, like contemporary brown bears, these bears appear to have lived almost exclusively on seafood.”
Prof Britton said it could mean the samples are of a subspecies of brown bear, but added it was also possible they were of polar bears.
The research has been published in scientific journal Annales Zoologici Fennici, external.
