You Say Mate-Guarding, I Say Marathon Love-Making

Antechinus is a small, carnivorous marsupial.

[I]n order to ensure breeding success, male Antechinuses strip their body of vital proteins and also suppress the immune system so as to free up additional metabolic energy. In this way an individual male trades away long term survival in return for short term breeding success, and following the breeding season there is a complete die-off of physiologically exhausted males... Males produce large amounts of testosterone and mate-guarding occurs in the form of protracted copulation (up to twelve hours in some species).

The females can store sperm for up to three days in specialized sperm-storage crypts in the ovary and do not ovulate until the end of the breeding season. Many litters have multiple-paternity (i.e. several fathers contribute to a single litter). Females can live for 2-3 years, however this is unusual, and most females die following the weaning of their first litter. Litters size depends on the number of teats in the pouch. There are as few as 4 teats, usually 8, and in some populations up to 10 can occur. It is currently unknown why teat number varies, however it is likely that in food-poor environments selection has tended towards fewer teats so that there is a greater parental investment per offspring.

An Antechinus baby can weigh as little as 4 grams and are some of the smallest Australian native animal babies.