As you cross the bridge, take a look to the left to witness some beaver activity. Although refuge staff remove the dam several times each year, the persistent beaver build it back up. Making dams creates ideal habitat, not just for beaver, but for frogs, turtles, fish, and waterfowl. Beaver have such an important role in the longevity of wetlands, they are considered a keystone species. A keystone species is a species that is vital to the survival of a certain ecosystem. Keep an eye out for other signs of beaver as you continue your hike.