Umbers KDL, Symonds MRE & Kokko H (2015) The mothematics of female pheromone signalling: strategies for aging virgins. American Naturalist 185: 417-432 PDF

What’s it about?

Moths are slightly unusual animals in that it is the females who advertise for mates, by emitting sex pheromone to attract males. Typically it is assumed that because the amount of pheromone they produce is truly tiny, that this behaviour has no cost to them. Using a theoretical modelling approach we demonstrate that, even if the costs are small, females will vary the effort they put into signalling as they age and remain unmated. Basically they will increase effort as they get older, rather than risk dying sad and lonely with their 60 cats in a bedsit. We then surveyed as much literature as we could get hold of to see what female moths actually do do (rather than what we just theoretically predict). Sure enough we found that they tend to ‘call’ for longer as they age, although the actual amount of pheromone they produce does not increase (we produce some nice models showing why the former strategy is a better bet for attracting more males). In addition to demonstrating, indirectly, that there is cost to pheromone signalling behaviour in female moths, our paper also highlights a whole bunch of areas of moth reproductive ecology that could really benefit from some research because we just don’t know anything about them (like, for example, whether females that call more attract more males – which is a fairly fundamental prediction from our paper).

What’s the story behind it?

Well, hands down, this was one of the most enjoyable and fun collaborations I’ve ever had (along with my Allen’s rule bird beak paper, coincidentally also published in American Naturalist, which is a journal I now have seriously good vibes about). The whole impetus for it largely came about through the dynamic, one might almost say febrile, brain  of Hanna Kokko, and through the lucky chance that I presented a talk about evolution of moth antennae at the 2011 Australasian Evolution Society conference in Townsville that she happened to take an interest in. I had been talking about how pheromone dynamics may have selected for the evolution of receiver structures and afterwards she asked me whether I would like to collaborate on testing a theoretical idea she had about modelling female moth signalling behaviour in regard to how much pheromone was put out by females (since I had some of that data). She had taken on Kate Umbers as a post-doc to work on the paper (to basically follow up on the numerous references I sent her way). So, the paper worked essentially with Kate writing the main structure of the paper, Hanna doing all the fancy modeling, and me as an eminence grise providing the moth pheromone biology expertise. It was a long slow process (three rounds of review at Am Nat), but it was never anything less than positive, in part because of my co-authors inability to send any email without some time-wasting internet link, shaggy dog story, witty bon mot or plain old fashioned pun (the title, which incidentally the journal editor really wasn’t keen on, reflects a small amount of the nature of our collaboration). If all collaborations were this rewarding then science would never be anything less than fantastic. That the paper itself is also, I think, a really good paper is a welcome bonus.


2 responses »

  1. […] behaviour  in moths in relation to population density, the latter following on, in part, from the paper on female signalling strategies in moths that I wrote with Kate Umbers and Hanna Kokko. Kita was the lucky honours student who took on the […]

  2. […] Do females moths choose their males by releasing small amounts of pheromone? Does this select for more sensitive males. We tested this through some simple field manipulations with the gum-leaf skeletonizer moth Uraba lugens. First we compared what kind of males turn up at traps baited with two vs. one female (the former representing double the pheromone amount, presumably). While this didn’t affect the number of males turning up, it DID affect the type of male. The males attracted to the single females had longer (more sensitive) antennae. Furthermore, age was relevant. Older females attract fewer males, but also the youngest females attract males with longer antennae, perhaps because they modulate their pheromone production to be choosier (as predicted by Umbers et al. 2015). […]

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