If the habitat does not have the necessary water level, beavers construct dams. Each dam is a little different. A beaver may work alone or with family members to build a dam, using piled logs and trees secured with mud, masses of plants, rocks, and sticks. Although the average tree used for construction of a dam is 4 to 12 inches (10–30 cm) across the stump, use of trees up to 150 feet (45 m) tall and 5 feet (115 cm) across have been recorded. As the tree snaps, the beaver runs! Very large trees are not moved but the bark is stripped off and eaten. Smaller trees are cut into moveable pieces, dragged into the water for repairing dams and lodges. This work is done mainly in spring and autumn.