Heavens to Betsy! Beavers have made such a comeback in Massachusetts that some now consider them a pest. From the New York Times article:
Around the nation, decades of environmental regulation, conservation efforts and changing land use have brought many species, like beavers, so far back from the brink that they are viewed as nuisances.
I, for one, gleefully applaud each and every time beavers build a dam and applaud twice as hard if it is a nuisance!