Opinions still divided on beavers
Do beavers have a positive or negative impact on the Scottish countryside? It is not as simple a question as it may seem.
Supporters of the Tay beavers point out the dams the animals build provide many benefits to other native species. Their opponents warn of damage to woodland and an increased risk of flooding.
The official Scottish Beaver Trial was meant to help settle the argument and provide scientific evidence which would allow politicians to decide whether a permanent reintroduction programme would be a good idea.
Knapdale Forest in Argyll was chosen as the location for the trial and the first beavers were released there in 2009.
The project is being run by the Royal Zoological Society of Scotland and the Scottish Wildlife Trust.
But it is being monitored by a dizzying array of experts from Scottish Natural Heritage, Oxford University, the Argyll Fisheries Trust, the James Hutton Institute, Stirling University, the Scottish Agricultural College, the Royal (Dick) School of Veterinary Studies, the Scottish Environment Protection Agency, Argyll and Bute Council, Historic Scotland, and even the British Dragonfly Society.
Make no mistake, this is a serious scientific experiment.Passionate campaign
Meanwhile, on the other side of the country, the Tay beavers have been busy doing what beavers do best. That, it seems, involves having baby beavers, lots of them, and all without the help of a single scientist.
Somebody must know who released the first beavers into the wild, but it is a closely guarded secret. It was, after all, a criminal offence under the Wildlife and Countryside Act.
Locals believe the release took place in 2001 and Scottish Natural Heritage now estimates the population in the Tay catchment is 100-strong.
Efforts to trap the animals turned into something of a public relations disaster for SNH, in the face of a passionate campaign run by a group of local people who believe the beavers should be left in peace.
Scotland's environment minister, Stewart Stevenson, is the man who had to decide whether to accept the beaver is back for good, or give the order for what was rather chillingly described as "lethal control".
Few politicians would view attempting to wipe out a species of furry animal which frequently appears in children's cartoons as a vote winner. So it is perhaps fortunate for Mr Stevenson that he had a third option.
Critics will claim that the minister has chosen to do nothing. Mr Stevenson argues he is simply planning to wait until the official Knapdale beaver trial is complete in 2015.
He will then be able to study the scientific evidence which has been gathered, before deciding whether the Argyll and Tay beavers should be considered permanent residents.
In any case, 2015 hardly seems a long way off when you consider that it is more than 400 years since beavers were hunted to extinction in Scotland. The Tay beavers certainly seem to be more than happy making up for lost time.