By Steven McKenzie
Highlands and Islands reporter, BBC Scotland news website
The demise of beavers began with the rise of Inverness
The deaths and disapearances of the Knapdale beavers are just the latest twists in the mammal's troubled Scottish story.
Hunted to extinction in the wild 400 years ago, more recent times have seen an illegally-released beaver found drowned on a seashore.
And last year, damaged trees recorded in Perthshire, Angus and Fife pointed to other unlawful releases of the animals.
The demise of Scotland's native beavers began with the rise of a Highland town.
The organisation Scottish Beavers believes the expansion of Inverness in the Middle Ages was a major factor.
The city became a key market for the animals' much prized pelt. Soft and thick, the coat is also waterproof.
Castoreum, a secretion produced in a gland below the tail, was sought after because it was believed to have health benefits.
The tail itself was also served as a substitute for fish.
Scotland's beavers were wiped out during the 17th Century. Their disappearance was followed by the extinction of other species.
Reputedly the last Scottish wolf was shot near Findhorn, Moray, in 1743 amid an outcry that it had killed two children.
Red kites were lost to Scotland in the 18th Century, before sea eagles and great auks vanished the following century.
Last year reports emerged of beavers being illegally released in the Scottish countryside.
Mystery surrounded the discovery of one found dead on a beach at Eathie on the Black Isle last April..
Police said it suffered a "cruel" death after ingesting a large quantity of sea water. Beavers are a freshwater species.