So, they are coming from your neighbour's property and felling your trees. I would think you could sue him for the price of the trees at maturity... that might open his eyes. Especially if you have video evidence. The arguement, in it's basic form, is that: you cannot regulate the beaver population on his land; his failure (negligence) to regulate the beaver population on his land is causing you harm; because he is the one who, through his negligence, is the cause of the problem, you are due compensation from him.

Any lawyers out there care to comment?

If you have no dam on your property at present, breech any dam as soon as they start to build it and breech it daily. They WILL get the message and move on. I have done this early in the spring and they gave up after about a week.

(Re the paint... is it non-toxic?)