Mating behavior in M. domestica is strongly tied to olfaction. Males habitually mark their surroundings with a chemical mark produced by a sternal gland. This scent likely serves as an advertisement to local females and a warning to local males. When a male and a receptive female meet, a precopulatory dance of sniffing, chasing, biting, and licking ensues. At the completion of this dance, the male immobilizes the female's hind legs and begins copulation, which lasts from 4 to 7 minutes. The majority of matings take place with the animals laying on their right sides.
Mating System: polygynandrous (promiscuous)
Sexual maturity in M. domestica is reached by 18 to 20 weeks. Gestation lasts 14 to 15 days and females can have up to 5 litters per year. Typical litter size is from 7 to 9.
Breeding interval: On average gray short-tailed opossums breed 4 times per year.
Breeding season: In the wild, breeding occurs most often during the spring and summer months, when daylight hours are the longest.
Range number of offspring: 1 to 15.
Range gestation period: 14 to 15 days.
Range weaning age: 3 to 4 weeks.
Average weaning age: 3 weeks.
Range time to independence: 6 to 8 weeks.
Range age at sexual or reproductive maturity (female): 5 to 7 months.
Range age at sexual or reproductive maturity (male): 5 to 7 months.
Key Reproductive Features: seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; induced ovulation ; viviparous
Average birth mass: 0.1 g.
Average number of offspring: 9.
Immediately after birth, newborn M. domestica crawl to their mother's stomach and attach to a nipple. They remain attached this way for 3 to 4 weeks. After detachment the young climb on their mother and/or follow her around for another three months or more. Paternal care in M. domestica is nonexistent, moreover, in captivity when fathers are confronted with their offspring, they act aggressively towards them.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)