The animal known for building a dam is the beaver. Beavers are large, semi-aquatic rodents known for their remarkable engineering skills. They create dams by felling trees and placing branches, mud, and rocks to block waterways. These dams serve several purposes: they create ponds that provide a safe habitat from predators, facilitate easy access to food, and help maintain water levels. By flooding areas, beavers promote wetland ecosystems, which support various plant and animal species. Their activities significantly impact local environments, contributing to biodiversity and influencing the water cycle, making beavers a keystone species in many ecosystems.