After Valentine’s Day? 3 Mate-Eating Animals
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.
Sadly, bad science continues to perpetuate a story that isn’t really true. The initial experiments on Latrodectus mactans – i.e. the ‘Black Widow’ – were set as the standard for the behaviour of the species. However, subsequent attempts to reproduce the results of the female eating her mate were unsuccessful. It was determined that in the initial experiment the females had not been adequately fed. Therefore upon completion of mating the female ate whatever was easiest to get – the male. Conducting reproductive observations on sated female Black Widows showed that a) the female did not eat her mate and b) that female Black Widows would cohabit with several males with out any sexual cannibalism.
So while a female Black Widow ‘can’ eat her mate, it is NOT an obligatory behavioural strategy in this species.
If one wants a ‘good’ story of ‘mating gone bad’, one should take a look at the reproductive behaviours of the Six-spotted Fishing Spider Dolomede triton. In this species the males compete to be the first one to mate with a newly emerged female. The male that mates with a female gets away after mating. However, after mating the behaviour of the female changes. Any male that attempts to court an already mated female is allowed to approach very close. Once he is ‘too close’ the female kills and eats the male. This isn’t ’sexual cannibalism’ (sensu strictu) but it is predation that capitalizes on sexual behaviour. In D. triton the population of adult males crashes as the number of mated females increases… to the point that there are no adult males left at all. Talk about getting even on a gender!