19 October 2011

Dancing with the invertebrates

If Peter Parker does whatever a spider can... he must be one hell of a dancer. And there’s some evidence for that.



(I will admit, that is not exactly what I expected to find when I Google searched for “Spider-Man dancing.”)

This video of the peacock spider (Maratus volans) went up early in March. It blew me away.





Finally, there’s a scientific paper that starts to describe this astonishing behaviour.

If you’ve just watched the video above, you can appreciate how restrained the scientific writing style for journal articles is. Instead of, “Wow! You have got to see this!”, we get, “Research on animal courtship has demonstrated that males of many species produce elaborate multi-component signals spanning more than one sensory modality.”

It’s not until the third paragraph in that Girard and colleagues let a little wonder slip in, calling the peacock spider, “an exceptional example” of spider courtship.

The paper contains a very detailed verbal display of the behaviour, and I don’t envy the task the authors had. Describing behaviour with just words is terrifically hard. Things start getting more interesting scientifically when they start to get to the parts of the courtship display that can’t be seen: vibration. I particularly love some of the names they give these signals. They call one kind of vibration signal... rumble-rumps.

Rumble-rumps! How can you not smile at that? And another kind is called crunch-rolls.

The vibrational seems to be a very important part of the courtship display, as these start when the male is still a long way away from the female. The authors note that this is very different from some North American spiders in this group, where the vibrational signals seem to ramp up when the males and females are quite close to each other.

Given the opening of this paper, I was rather expecting that there would be some suggestion about which of all these cues the females are important for the females. Unfortunately, there is not found in this paper. To get the best filming condition of the male courtship, the experimenters resorted to pulling a dirty trick on the males: they weren’t courting live females, but rather dead females, mounted into a life-life posture. I know it sounds slightly creepy, but animal behaviour scientists have been resorting to such tricks for many decades. Imagine the poor little male spider’s thoughts: “I’m dancing my fan off here! Sheesh, what more do females want?”

This is such a rich behaviour that it’s no doubt going to take years and years of research before we begin to understand it.

Reference

Girard M, Kasumovic M, Elias D (2011). Multi-modal courtship in the peacock spider, Maratus volans (O.P.-Cambridge, 1874). PLoS ONE 6(9): e25390. DOI: 10.1371/journal.pone.0025390

(The creator of the YouTube videos, J├╝rgen Otto, is not an author on this paper, but is thanked for helping to collect specimens.)





Breakin’ Spider-Man from here; balletic Spider-Man from here.

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