Fickleness is an odd thing. Why change your mind for no good reason? Well, if you are a fish, and picking a mate, predators may well be that reason. Choosing a mate is hard enough, especially when you have to invest a lot in reproduction and females often invest the lion’s share in reproduction (perhaps a topic for another day, but if you are interested look up Bateman’s principle). But imagine a choice in a variable environment. If you are struggling here, think about your own life… we don’t make decisions easily and everything is wrought with contingency. ‘I want to wear my shiny new acrylic sweater, but what if it gets too hot? Or I end up too close to a heater and combust?’ These are trials of modern life, and actually, just life in general. Animals are also faced with contingency. Case in point, ‘who to mate with?’ is a vital question but one that could change depending on circumstances. In the hight of the Jersey Shore craze, hooking up with ‘The Situation’ might seem like a good idea, but maybe not sound so hot in the days, months, or years after. Similarly, fish make choices of shacking up based on local pressures. Bierbach (pdf) and colleagues found that female mollies will change their choice of mates from the showy males with impressive displays and dreamy eyes to the wimpy, inconspicuous, males when predators abound. So hooray for the underdog! Dorks win at last!
When times are good, or risk is low, females want the bestest-showyest males around. When times are tough they want the males which are least likely to get them killed. See, having an elaborate display, flashy colors, or obscenely expensive cars, all make you a bit of a target for predators, and the female who choses one of these showy males could 1) risk getting caught up in that mess, and 2) having kiddies that act like their daddy and also find themselves in ‘sticky situations’. So, is this revenge of the nerds? Well, not so much. While Bierbach and co. found this switch in behavior in naive mollies, experienced mollies were a whole different story. They just plain didn’t give a shit. Badasses. The authors suggest that females who’ve grown up in the mean streets of Mexico’s waterways know how to handle themselves. An alternative explanation (which is mine, all mine) is that knowledgable female mollies that are on the prowl think that any male that managed to grow up to be so impressive, and showy, and dreamy, WITHOUT already having his ass handed to him by a predator has probably got something going for him, because if not – he’d be dead.
So the wimpy males are left in the cold anyway. Well, probably, but there is a glimmer of hope (my baseless speculation). If showy males are really more likely to be eaten, perhaps the wimps get a statistical shot at getting laid. Even if their odds of mating are low compared to their show-off counterparts, their odds of dying are even lower. So perhaps they live to be a wimpy second choice for a disappointed mollie another day.
Oh, and one more cool thing about this paper, it was the result of a field course! Good work students!
REF: Bierbach et al. 2011. Predator-induced changes of female mating preferences: innate and experiential effects. BMC Evolutionary Biology 11:190 doi:10.1186/1471-2148-11-190