Eurasian Harvest Mouse

The Eurasian harvest mouse is a minute climbing rodent, only 55–75 mm from nose to rump and usually 4–11 g. Reddish-brown upperparts contrast with a white or cream belly, while the relatively large eyes and ears suit life among dense stems. Its most distinctive feature is a nearly body-length, sparsely furred prehensile tail. Broad hind feet and a partly opposable outer toe let it grip vegetation while the forefeet gather food. (Wikipedia, Eurasian harvest mouse account)

Harvest mice live among tall grasses, reeds, sedges, hedgerows and cereal crops across Europe and Asia. They climb vertically with the tail acting as an extra limb and feed chiefly on seeds and insects, supplemented by nectar and fruit. Females weave spherical breeding nests from grass leaves and fasten them above ground to living stems; young develop their climbing grip before weaning. The source opened for this entry did not describe Mongolian localities, so none is suggested here. (Wikipedia, Eurasian harvest mouse account)