National Geographic : 1955 May
O National Geographic Society 669 Ektachrome by Willis Peterson Beaver's Paddlelike Tail Serves as a Rudder Afloat, a Dining Stool Ashore Vegetarians, beavers prefer the soft bark of aspens, willows, and cottonwoods, but they also feast on aquatic plants. This peeled trunk may be chopped into portable lengths for dam construction. When the beaver smacks its tail ker-slap! on quiet waters, companions heed the danger signal and dive to safety.