Plant-eating mammals abound in the trees of the deciduous forests, eating shoots and leaf buds in the spring and fruits and nuts in the autumn. The chirit is a typical plant-eating mammal. Its peculiar shape is a legacy from an immediate ancestor, the chiselhead of the northern coniferous forests. As it spread south into the temperate woodlands it found that it no longer needed to make deep tunnels in the trees to escape the harsh winter, and as a result the animal's specialized chiseling and gnawing teeth became smaller, its dentition reverting to be more like that of its distant ancestor the eastern grey squirrel. Its bodily shape, however, was still perfectly adapted to life in the trees and remained unchanged.
Now that the animal no longer led a burrowing existence, its legs and feet had to evolve to suit its new environment. Its hind feet, although small and short, became very powerful and developed strong, gripping claws. The underside of its short tail grew hard and scaly and with its hind feet formed a strong three-point anchor that could secure the animal to the tree while it reached out to collect food.
As its ancestor's jumping ability has completely disappeared, the animal can only move from one tree to another by reaching out and grasping an extended branch. For this reason the chirit is found most often in dense thickets, where the trees are close together. Its only enemies are birds of prey, and it is really only vulnerable to these when feeding in the topmost branches. It retains the predilection of the burrowing squirrel for making nests in holes in trees and often occupies holes and hollows excavated by wood-boring birds.