Nest Structure Dynamics and Seasonal Use of Nests by Siberian Chipmunks (Eutamias sibiricus)

Abstract

Nest use by the Siberian chipmunk ( Eutamias sibiricus ) was observed in an oak ( Quercus ) forest in northern Japan for 7 years. Nests were located in underground burrows or tree hollows and, except for mothers with young, were occupied by single animals. Tree nests were not used for hibernation or parturition. After emergence from hibernation, many individuals abandoned their spring burrows. Adult males used tree nests or spring burrows of other individuals as summer nests, whereas females either used their own spring burrows or new burrows for parturition. Most residents used the new burrows for hibernation. Frequent change of nest sites is probably an antipredator strategy. Excavation of 17 burrows revealed differences in burrow structure before and after hibernation. In the preparation period, burrows consisted of one main tunnel and one nest chamber. When the hibernation stage started, a plug of soil was made at the entrance. Usually in late November, a large amount of soil was expelled from the entrance and soil was packed tightly into the main tunnel. This soil was taken from one or two new subtunnels dug below the nest chamber. In spring a new tunnel was dug to the surface. The soil resulting from digging the new main tunnel was packed into the subtunnels. There is a relationship between burrow structure and social organization among chipmunks. E. sibiricus has a simple burrow system and does not hold individual territories, whereas Tamias striatus has an extensive burrow system and holds individual territories.