Landowners have been accused of shooting heavily pregnant beavers, or ones that had recently given birth.
The claims have fuelled demands for shooting to be restricted in the breeding season and renewed calls for legal protection for Scotland’s beavers.
The animals are often regarded as a pest by landowners and farmers, who complain they gnaw at trees and cause flooding in fields next to rivers and burns.
Despite the creatures being hunted to extinction in the 16th century, Scotland now has two beaver populations – in the Tay River catchment area and an official trial re-introduction area at Knapdale Forest in Argyll.
Experts at Edinburgh Zoo conducted post-mortem examinations on 23 beavers from Tayside. Following a freedom of information request, it emerged that two, nearing full-term, had been shot as had two others which had recently given birth.
There were also concerns about how long some of the beavers had taken to die. At least one body contained lead shot – it is against the law to use lead shot to kill an animal in water.
The Royal Zoological Society of Scotland said: “In our capacity as advisors to the Scottish Government on beaver management, RZSS has written both to Scottish Natural Heritage and the Scottish government to raise welfare concerns over a small number of deceased beavers sent in by landowners.
“This specifically relates to how they were shot, the distance they were shot from and, most significantly, the timing of dispatch, particularly of females with dependent young still in the lodge. We are currently awaiting a response from the minister before making any further comment.”
Nick Halfhide, Scottish Natural Heritage’s director of operations, said: “We share welfare concerns about beavers shot with inappropriate firearms and ammunition, and those with dependent young.
“We have asked land managers not to shoot beavers in Tayside but instead seek advice from us on mitigation, such as protecting trees.
“However, if they choose to use lethal control, we have offered them advice on how to do so humanely.”