Forest evidence of the yetis can be found in footprints, hairs, and local sightings. The yetis are also fairly handy at construction. Burtsev continues, "They make strange pyramidal constructions of trunks and branches in the wood - sometimes 3 or 4 meters, sometimes only 30 cm high. Sometimes they bend huge trees and twist their trunks like wheels. A human being is just not strong enough for that, and there seems to be no need for bears to do this. At first, we thought that yetis do this to make shelters, but then we came to the conclusion that this is a sort of landmark for them. Or, maybe, this is a way for a yeti to say something to its congeners."