The Antechinus, a small marsupial from Australia, has a unique and deadly mating system. Males engage in frenzied mating for up to 14 hours over a two to three-week period, driven by surges in testosterone and cortisol. This leads to organ failure and death. Rarely, some males survive but become infertile. The mass male die-off provides food for pregnant females and surviving males, with females sometimes cannibalizing the males. There are 15 species of Antechinus, all exhibiting this extreme reproductive behavior.