Killer Marathon Sex
The antechinus is a small, mouse-like marsupial. Male antechinuses are not afraid of death. In fact, they are willing to give up their life just to pass on their genes and create a new generation. Male antechinuses take mating so seriously that when they have sex, they copulate almost continuously for two to three weeks until they die of exhaustion. During these weeks, they run around the forest from mate to mate and have sex with each one for up to fourteen hours straight. Mating with so many different partners takes such a toll on male antechinuses that their immune system crashes because of a massive release of hormones, their fur starts to fall out, and they bleed internally. As a result, female antechinuses are left alone to raise their offspring.
Pleasing a female praying mantis is not easy, especially because there is a constant risk of being killed. To impress the female and convince her to mate, a male mantis first needs to show off some slick dance moves. If the female mantis thinks his skills are good enough, she will let him copulate with her. But if he fails to impress her, she will not hesitate to eat him on the spot. In either case, the female mantis may choose to chew the head off her male partner to increase her fertility and ensure the survival of her species. Although sexual cannibalism may seem cruel, it indirectly benefits male mantises by increasing their investment in offspring. A female mantis tends to lay more eggs if she engages in sexual cannibalism with a male.