They weigh 1.9 g at birth. Hair appears at eight days. Their eyes open at 9 to 15 days, depending on how much milk they can get from their mother's eight teats. They drink milk from their mother until they are 17 to 21 days old. They leave the nest when they are only three or four weeks old.
Young females can mate when only three months old and give birth when four months old.
Males born in March can mate by mid-summer. Males born in late summer or later mate the following spring. Southern red-backed voles can live for one year in the wild. A few live for two years. Most die before they are three months old.