Beavers are devoted to their work as dam builders and they are born equipped and ready for the job. Leave it to Beavers tells the story of beavers in North America – their history, their near extinction, and their current comeback as modern day eco-heroes. The program airs Wednesday, May 14 at 8 p.m. (ET) on PBS (check local listings). Beavers’ continuously growing, self-sharpening incisors strengthened with iron are the perfect tools of the trade. Not only do they help beavers fell the hundreds of trees they need to dam a river, they also come in handy for meals because beavers are vegetarians that gnaw through bark to eat the sugary layer underneath.