At night an adult beaver is occupied with cutting down a 30 cm thick polar. The trunk is already half cut in. Small yellow bark chips and relatively big corewood chips are lying around the tree. The beaver is cutting right-sidedly (=the right side of the head is turned upwardly) and left-sidedly. It always keeps its head in the same angle to the vertical running wood fibre. It expands the notch beyond the centre of the trunk. During and between the gnawing periods, the bever wipes the chips off the notch with its hands. In short breaks, the gnawing teeh are whetted. Finally, the deep, one-sided notch makes the poplar fall down. The bever cuts off an arm-thick branch and trails it away. Then it divides a neck-thick trunk. The notch is widened only to head-size. By numerous bites the notch is deepened; then the beaver raises its head, clens its mouth from the wooden chips and sits up to look around. Having made a cut around the trunk, the beaver raises it and the trunk breaks into two parts. The bigger one is trailed away in a right-sided transport.