Residents on Colonsay have been intrigued by the three carcasses with some suggesting they could be polar bears washed down from the Arctic.
But scientists at the Scottish Marine Animal Strandings Scheme said they were more likely to be marine animals.
They said decomposing blubber has a fur-like appearance.
The Friends of Colonsay Facebook page has carried a series of photographs of the remains, which look like they are covered in dirty white fur.
The group speculated on the possibility of the remains being those of bears, but has since acknowledged the scientists' explanation.
Inverness-based SMAS carries out examinations of whales, dolphins and other large marine animals found washed up on Scottish beaches.
On the Colonsay discoveries, it said: "We have had a number of these sort of cases over the years, and are confident that these are highly autolysed cetacean carcases.
"The 'fur' referred to is decomposing blubber, which becomes stringy in appearance as the lipids from the blubber are drained into the sand.
"Once the bones are exposed we may be able to identify these animals to a species level with help from the experts at the National Museum of Scotland."
The Royal Zoological Society of Scotland, which has three polar bears at its Highland Wildlife Park, has also said it did not believe the remains to be those of bears.
Six years ago, RSPB Scotland did an April Fool's Day joke about a polar bear being washed up on the Isle of Mull to highlight concerns about climate change.
Though not reaching as far as Scotland, polar bears are known to stray far from their usual range.
Earlier this year, a polar bear was shot dead in northern Iceland, the first such incident of its kind since 2010.
The female bear came within 500 metres of an inhabited farm before it was shot by a marksman.
Scientists believe mysterious "fur covered' remains washed up on a Scottish island could be those of dead sea mammals such as whales or dolphins.