Sorry guys: female sexual cannibalism is far more common than male. In some species, males provide the single biggest food source for the females of their kind. While scientists have postulated all kinds of evolutionary reasons for sexual cannibalism, their theories are often confounded by three core conflicts:
- it prevents males from further mating
- many male mates avoid being eaten if possible
- males are usually eaten before they can even mate
So while there might be an adaptive reason for these relationships it is equally likely that the (usually much larger) female might just decide that a given male will make a better meal than a mate.
1) Scorpions are everywhere – mountains, deserts, tropics, caves and even post-nuclear blast sites. Nonetheless, scorpions have as many predators as they do habitats, including various mammals, frogs, salamanders, insects spiders and birds. However, did you know that their own biggest predator is themselves? Over half of sand scorpions prey on scorpions and in many species the female consumes its mate, while in rare species the reverse is true.
How the Males Escape (Sometimes): Many males have been observed to sting the females into stunned submission prior to the mating process as well – presumably in part to limit their chances of beaten eaten alive afterward.
2) Spiders are one of the most widely recognized mate-eating animal types in the world, with one kind – the so-called Black Widow – notably named for this habit. So why do the females consume the males, in some species at a rate of over 80%? Many theories have been advanced to explain this but the most solid explanation seems to be simply a matter of size: in species where the female is significantly bigger the females much more frequently eat the males. In short, it isn’t about fuel for the pregnancy or an evolutionary adaptation – it is a simple natural slaughter of opportunity.
How the Males Escape (Sometimes): Some male spiders hold the jaws of their female mates open while mating in order to keep from being eaten alive – others bring a diversionary meal to distract their partner.
3) Praying mantises are anything but penitent in the act of mating, infamous for often biting off the heads of their male partners during the act itself (which, amazingly, only speeds things up). Some males appear to wait for an ideal opportunity to dismount without prompting the female into a cannibalistic rage, though scientists have yet to determine and still debate which is the more adaptive trait for the males: permitting their own consumption in order to complete the process and improve chances of fertilization or making a clean getaway to mate again. Large mantises have been known to eat lizards, mice and small birds – making a male a small snack.
How the Males Escape (Sometimes): The best known self-preservation tactic for male mantises is simply waiting until their partner has caught a snack – and to hoping she isn’t still hungry after they finish copulating.