I wonder if our aspen, which seems to have such difficulty in reproducing sexually here, is constrained by the same limitations as North American cottonwoods and if so, to what extent the absence of beavers in Scotland for some hundreds of years, coupled with all the changes to rivers (drains for agriculture, etc.) and land management (heavy grazing) have had in making it difficult for aspen to reproduce sexually.
This evening I went out to check one of my trail cameras. Here is one of the clips of film. A yearling (I guess) beaver is gnawing at a small branch, takes a break to groom itself and then goes back to feeding.