The Thoughtful Animal

What’s the best way for a lonely guy to get a date? If you’re a Splendid Fairy-Wren (Malurus splendens, native to Australia), your best bet might be to frighten the object of your affection.

You’ve learned all about the birds and the bees; now it’s time to learn from them.

i-ad627e5be2d52d48895099980a4c0699-Splendid_Fairy-wren_male-thumb-225x181-60676.jpgLots of research has shown that animals reduce their sexual behaviors when predators are around. After all, it isn’t just potential mates who would see or hear an elaborate mating display, but also potential predators. The male splendid fairy-wren does something a little bit unusual, though. Gray Butcherbirds (Cracticus torquatus) are known to prey upon splendid fairy-wrens and their nests. Almost without fail, whenever the call of the gray butcherbird is heard, male fairy-wrens begin singing! Specifically, they sing a short trill referred to as a “Type 2 song.” In fact, researchers Greig and Pruett-Jones have gone so far as to refer to the double-call as a “duet.”

ResearchBlogging.orgWhat would cause the male splendid fairy-wrens to respond to the calls of their predators in such a strange way? One possibility is that the response of the fairy-wrens is an alarm call, meant to warn others nearby of the presence of a predator. One experiment ruled out that possibility, though: male splendid fairy-wrens give their Type 2 songs in response to hearing the vocalization of the butcherbird, but not in the presence of silent butcherbirds. Another possibility is that the Type 2 songs are meant to scare the butcherbirds away, but another experiment indicated that this wasn’t the case either, as males were no more likely to sing their Type 2 songs upon seeing a silent butcherbird. It seems, then, that there is something special about the vocalization of the butcherbird that causes the splendid fairy-wren to sing its Type 2 song.

It could be that the Type 2 song functions as a territorial display, to keep other males away. If the Type 2 song is used as a territorial display, Greig and Pruett-Jones predicted, then males would respond to Type 2 songs coming from encroaching males in an aggressive way. This, however, is not the case either.

Alternatively, it might be the case that the Type 2 song functions as a mating display: a way to attract the attention of the females. In this case, the Type 2 song may occur following the butcherbird call simply because that predatory call is particularly salient; in other words, if females become more aware of their surroundings after a butcherbird call, then they will be better able to detect the males’ Type 2 song that immediately follows. This predicts that female splendid fairy-wrens should become more alert and attentive following the butcherbird call. If this is the case – if butcherbird calls essentially facilitate the detection of the Type 2 song – then females should be more responsive to the Type 2 song when it follows a predatory butcherbird call, rather than in isolation.


To address this question, the researchers conducted a series of experiments utilizing pre-recorded butcherbird calls and splendid fairy-wren Type 2 songs. They found that females did preferentially attend to the calls of the butcherbird compared with other non-predator calls. In addition, females tended to sing more in response to the males’ Type 2 song when it was preceded by the butcherbird call than to solo Type 2 songs. It is not clear what the meaning of the females’ response call is – it could be positive (“here’s my phone number, call me!”) or negative (“not a chance, dude!”), but whatever its purpose, it is certain that it occurs in response to the males’ Type 2 songs.

So when the female splendid fairy-wrens are scared by the predator calls, they seem to become more responsive to male Type 2 songs. This phenomenon has been recorded in humans, as well, but in reverse.

In 1974, University of British Columbia psychologists Donald G. Dutton and Arthur P. Aron were studying human attraction, and in one particularly brilliant experiment, they took advantage of a local river.

There are two bridges along the Capilano River in North Vancouver. The Capilano Canyon Suspension Bridge is a five foot wide, 450 foot long, bridge made of wooden boards attached to wire cables that run from one end of the canyon to the other. The authors noted that it has several anxiety-inducing features, including, “(a) a tendency to tilt, sway, and wobble, creating the impression that one is about to fall over the side; (b) very low handrails of wire cable which contribute to this impression; and (c) a 230-foot drop to rocks and shallow rapids below the bridge.” This served as the “experimental” bridge. By contrast, the “control” bridge was “constructed of heavy cedar, this bridge was wider and firmer than the experimental bridge, was only 10 feet above a small, shallow rivulet which ran into the main river, had high handrails, and did not tilt or sway.”

i-0b3d533b79e14215099fa731f3e7c6ed-800px-CapilanoBridge-thumb-500x305-60677.jpg

The Capilano Canyon Suspension Bridge

Male travelers, naive to the experimental set-up, would pass by along either bridge, and after crossing, would be approached by an attractive female experimenter, who would ask them to fill out several questionnaires including the Thematic Apperception Test, which requires individuals to write a story based on a series of pictures. Not only were the men who walked across the fear-inducing shaky bridge more likely to include sexual content in their stories than those who crossed the stable bridge, but they were also more likely to flirt with the experimenter and ask for her number. It’s as if they misunderstood their anxiety-induced physiological arousal – elevated heartrate, sweaty palms, and so on – as reflective of sexual attraction and desire. This is not to say, of course, that the mechanism underlying this phenomenon in fairy-wrens and humans is necessarily the same, even if the outcome is analogous. Whatever the mechanism, it turns out that human men, as well as female splendid fairy-wrens, are more likely to be receptive to or interested in mating-related behaviors following a fearful situation.

Perhaps that’s why the scary movie is such a common dating ritual.

Greig, E., & Pruett-Jones, S. (2010). Danger may enhance communication: predator calls alert females to male displays Behavioral Ecology, 21 (6), 1360-1366 DOI: 10.1093/beheco/arq155

Greig, E., & Pruett-Jones, S. (2009). A predator-elicited song in the splendid fairy-wren: warning signal or intraspecific display? Animal Behaviour, 78 (1), 45-52 DOI: 10.1016/j.anbehav.2009.02.030

Dutton DG, & Aron AP (1974). Some evidence for heightened sexual attraction under conditions of high anxiety. Journal of personality and social psychology, 30 (4), 510-7 PMID: 4455773

Images: Splendid Fairy-Wren, Wikimedia Commons/Julia Gross, Capilano Suspension Bridge, Wikimedia Commons/Leonard G.

Comments

  1. #1 Tracey S.
    January 26, 2011

    Interesting. The question is are the females more attracted to the male’s song when they hear it after the predator because they think the male will somehow protect them from the predator, or are they just impressed with a male who will flirt with danger because it somehow indicates that he must be bigger/stronger/more fit if he’s not afraid of a predator. Not sure there’s a way to measure that.

    Unfortunately, the human study only shows that danger makes males more impressed with themselves and horny, which doesn’t say anything about evolutionary advantage because it doesn’t matter how attracted they are if it doesn’t turn on the females at all (although the increased confidence after facing danger may lead to increased success).

  2. #2 Jason Goldman
    January 26, 2011

    Good points. With respect to the birds, though, the females may not need to be more attracted to the song, per se, when it follows the predatory call. Rather, the predatory call may simply serve to enhance signal detection in the first place. Also, to serve as an example of honest signaling theory/Zahavi’s handicapping principle, I think that the males’ tendency to sing following the predatory call would have to covary along with other things that also correlated with increased fitness (like body size, for example), but in this study, males that sang in response to the Butcherbird calls did not differ significantly in any measured social or morphological trait compared to the males that did not sing in response to the Butcherbird calls.

  3. #3 TheBrummell
    January 26, 2011

    I’ve often encountered an anecdote in fiction that is based on a similar set of circumstances. In the low-end science fiction and fantasy I tend to read, the protagonists are often thrown into frightening, stressful situations. Once the crisis is resolved, everbody – male and female, human and demihuman – gets horny. It’s just accepted that crisis -> sex.

    Maybe I just need to read better literature.

    Also, I’ve been to the Capilano Canyon Suspension Bridge, but never across it – because it costs money! There’s a similar bridge with free access a few kilometres away in Lynn Canyon. I don’t know if it’s quite as high above its river, but it is certainly high enough for the fall to be lethal, and at both ends of the Lynn Canyon Suspension Bridge there are markers and memorials to people (mostly, but not entirely young men) who have died as a result of falls at Lynn Canyon near the bridge. I’d be interested in a further comparison involving the Lynn Canyon bridge, to see the effect of shelling out $10 to get one’s adrenaline fix / arousal vs. unlimited runs back-and-forth for free over a known killer bridge.

  4. #4 Chrisj
    January 26, 2011

    I confess my immediate thought was “how did they blind randomise who went over each bridge without giving the game away”. Without access to the 1974 article I can’t be sure, but I imagine they didn’t. So I can’t help but wonder what testing they did to make sure that causality didn’t run the other way – perhaps men of certain types were more likely to cross one bridge than the other….

  5. #5 Jason G. Goldman
    January 26, 2011

    @Chrisj (#4): The researchers recognized this problem as well, and conducted a second experiment, using only individuals who were about to cross, or had already crossed the suspension bridge. They write, “To avoid this latter problem, control subjects who had just crossed the bridge and were sitting or walking in a small park were contacted at least 10 minutes after crossing the bridge. This strategy, it was hoped, would rule out residual physiological arousal as a confounding factor.”

    In other words, in this experiment, the experimental group consisted of anxious individuals who were just about to cross the bridge, while the control group included individuals who had already crossed the bridge and whose physiological arousal had ostensibly returned to baseline. The results of the first experiment (described in the post) were replicated in this follow-up experiment as well.

  6. #6 Chrisj
    January 26, 2011

    Thanks for the details, Jason; that does indeed sound like a good approach.

  7. #7 Colleen McCaffery
    January 26, 2011

    I just *knew* the bridge experiment was going to enter at some point-I thought of it immediately when I read about the birds.

    Has the experiment been done on female humans I wonder? I suspect would be the same…which might explain why fire fighters and “hero rescues” are so darn…well, hot. (yeah, like I’m always being rescued by cute fire fighters…though there was a very cute paramedic who pulled me out of a car wreck once…I sort of think my split open head was a bit off putting though…not to mention that I vomited on him.)

    Anyway, I am hoping if my husband ever gets trapped in an elevator that he isn’t in there with a cute woman.

    I also wondered if perhaps it is not so much misattributed anxiety-induced physiological arousal, but rather some mechanism to spur on a coupling under dire circumstances. In other words under precarious circumstances a way to at least have one last shot at fertilizing something (you know, before you fall to your death off a bridge, or whatever?)

  8. #8 Jason Goldman
    January 27, 2011

    Colleen (@6): Interesting hypothesis. Actually, the physiological arousal hypothesis is pretty well established. For example, you see similar results in males following the administration of electric shocks, for example. Increased sexual imagery on measures like the Thematic Apperception Test has even been found in college classrooms following being berated by the professor.

  9. #9 Colleen McCaffery
    January 27, 2011

    Jason (@8): Interesting! I’ll look into the physiological arousal hypothesis some more then. I now find myself wondering how this response may or may not play into things like sexual assault… just layperson musings.

    My takeaway is that ladies may wish to bring tasers on dates, in case there are no natural sparks.

    Just kidding, of course. Berating your date sounds like much for fun.

    Great post!

  10. #10 sally
    January 27, 2011

    but wait… i think they need to interview these bridge crossing men before they cross the bridge. might these results indicate that men who would dare to cross such a scary bridge are more likely to flirt & include sexual content in any story they tell than men who wouldn’t dare cross the thing?

  11. #11 informania
    January 29, 2011

    Too bad no testosterone measurements were taken in the bridge experiment..

    Also, I’d like to argue that the subjects were in fact not in an anxious state anymore, and the effect might be due to overcoming the anxious state instead of to the state itself.

  12. #12 informania
    January 29, 2011

    comparison with responses from men who didn’t make it (of course not the hard way) to the end would be usefull also

  13. #13 capsiplex
    January 29, 2011

    My takeaway is that ladies may wish to bring tasers on dates, in case there are no natural sparks.

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