The inactive season, from May-September, is hibernation season for B. parvus . From September through December, B. parvus is in an active season of breeding. B. parvus females are polyestrous but limited to one litter per year by the need to store fat reserves for hibernation. Without sufficient fat, the females die. In response to fat reserve limitations, B. parvus synchronizes its reproduction with spring, when nutrient rich Bogong moths are abundant.
Breeding occurs annually for many consecutive years.
Reproducing females have been found up to 12 years of age, which makes them one of the longest lived small terrestrial mammals. Mating occurs between late September and mid October. The young have well developed forelimbs and heads for traveling from the cloaca to the pouch. Frequently the female bear smore than four young, leading to more offspring than teats. Under these circumstances, the 'slowest' young will not have a teat when it arrives in the pouch, and will die.