Wildlife charities have called on the First Minister to act to give beavers in Scotland legal protected status and prevent unregulated culling.
Organisations including the Scottish Wildlife Trust, the Scottish Beaver Trial, National Trust for Scotland and the Royal Zoological Society of Scotland signed an open letter to Nicola Sturgeon urging action.
Beavers were spotted in Tayside in 2006 due to unauthorised releases, four centuries after they were hunted to extinction across Scotland.
An official reintroduction programme has taken place in Argyll.
Environment secretary Roseanna Cunningham told MSPs a year ago that legislative changes to ensure beavers are given European Protected Status would be laid at Holyrood in the first half of 2018.
The letter states: “The clock has run out on the statement, made by the Scottish Government on 20 December 2017, that legislation to make beavers a protected species in Scotland would be laid before Parliament in the first half of 2018.
“We are calling on the First Minister to renew her government’s leadership and commit to bringing home a former resident.
“Pioneering work including the Scottish Beaver Trial and the experience of reintroductions in more than 20 European countries shows beavers have the potential to bring enormous positive change.
“They breathe new life into our landscape by creating dynamic woodland and wetland habitats, and they help to control flooding by slowing down upland streams.
“It is now more than two years since the Scottish Government announced in November 2016 that it was minded to allow beavers to naturally recolonise Scotland.”
The letter points out without legal protection the animals can be culled without regulation.
Scottish Wildlife Trust Conservation Director Susan Davies said it is “hard to understand the reason for the delay”
She added: “Without protection beavers are subject to unregulated culling, which raises questions about their welfare and how they are being prevented from naturally spreading throughout Scotland.”
A Scottish Government spokesman said: “The return of beavers to Scotland’s countryside demonstrates our commitment to protect and enhance biodiversity.
“We have now completed the technical assessments required and expect to bring forward European Protected Status legislation next year, along with a management system that protects agriculture and other land uses.
“It is important that we build support for beaver management measures among all stakeholders, especially where beavers are having a serious impact on some of our most productive farmland.
“We have made very good progress in this respect and hope to resolve some outstanding issues in the new year.”