Both Millardia and Cremnomys sometimes are considered only subgenera of Rattus.
Females have six mammae.
The length of the tail is thought to be an adaptation to movement among rocks. During 1968 there was a drought in this area, and only a single pregnant female was found from November 1968 to April 1969. In 1970, however, the rains exceeded the normal level, and pregnant females were taken from March to October, with a peak in August. Litter size averaged four and ranged from two to eight young. The Johns Hopkins University Press.