| Nature's Engineers Build Dams for Us | |
| about beavers | * They are the world's second-largest rodents. * They are up to 30 kilograms in . * They are nature's great builders. |
| What beavers build in the Vltava River area | * A family of eight beavers built a dam in the Vltava River area,while the local officials couldn't make it done because of having building permits. * So far,the beavers have built at least four dams in the Vltava River area. The one can be seen from space. The beavers picked perfect places to build their dams and their designs are better than . |
| ★ beavers build their homes | ① They put sticks and wood into the mud of the riverbed to form the base of a dam. ② They use materials rocks and mud to build the top of the base. ③ They build the dam across the river. This creates a large "beaver pool". ④ They build homes in the pools,which offer them food and them from enemies. |
| ★ Why beavers' work is for the environment | * Beaver dams make good homes for many other animals,like frogs and fish. * Beaver dams can help stop from spreading. * Beaver dams help prevent flooding. |

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