The Australian government has added two species of antechinus, the black-tailed dusky and the silver-headed, to its endangered species list, saying all that sex is killing them. During mating season, which lasts for several weeks each year, males and females move frantically from one mate to another. There's no courtship, just sex -- with as many partners as possible. Baker explains that while both males and females get stressed, only the males produce testosterone. The constant high levels of testosterone keep the stress hormone, cortisol, from shutting off.

Source: CNN May 15, 2018 16:18 UTC