The sound is half the fun so don’t forget to turn up your speakers. It seems like it must be a part of some research project with the fancy recording set up but I’m not sure who made it. Anyway it seemed pretty cool, so I took a quick look at the literature to see what was going on.
At first glance, it looks like the spider is making the noise with his front legs but it turns out that, according to research by Noordam, he is actually using a specialized hardened region on the bottom of his abdomen to
bang on the ground at the same time he moves his arms (). If you look closely on the video you can see his tail end moving up and down in time with the sounds.
Rypstra, Wieg, Walker, Persons found female spiders are more likely to copulate if the male does more arm and body shakes. On the other hand, the male is more likely to work harder at his jitterbug if he can detect pheromones indicating the female has not yet mated. Next time I see a couple spiders together, I’m going to be looking for dancing.
Dale Hoyt left a helpful comment that points out that the abdomen isn’t actually touching the ground when when the sounds are being made. I had assumed it was a trick of the lighting but looking closer now, there really doesn’t appear to be any contact. Luckily he suggested the search term “stridulation” (a shrill grating, chirping, or hissing sound made by rubbing body parts together) that produced much better results from the literature. The video may have been from (or based on a) study by Elias, Mason, Maddison and Hoy where they studied the vibrational aspects of spider dancing. Their experimental setup sounds a lot like what’s in the video:
The arena substrate floor for courtship was a sheet of graph paper attached to a square cardboard frame (60 cm×45 cm). Females were tethered as above [anesthetized with CO2 and attached to a wire with low melting point wax], and the male’s seismic signals recorded using a piezo-electric sensor placed directly underneath the tethered female.
Didn’t seem to bother the male much that she was unconscious and restrained. Anyway, the researchers found three different types of seismic signaling and labeled them (using highly technical terminology): thumps, buzzes and scrapes. They made a really cool figure that demonstrates each of the types:
Top panels show body positions, with numbers (1–5) illustrating movements of the forelegs and abdomen. Middle panels show the position of one of the forelegs (mm above the substrate). Bottom panels show the oscillograms of the seismic signals.
Thump signal: Front legs come down (1–2), contact the substrate and quickly move back up (2–3). Shortly afterwards the abdomen is pulled back and released, and the abdomen ‘rings’ at 58.3 Hz (4–5). Thumps are broadband signals with peak frequencies at 203 Hz and 1203 Hz. Production of signal corresponds with the percussive contact of the front legs against the substrate (1–2) and movements of the abdomen (4–5).
Scrape signal: Abdomen moves up (1–2) and shortly afterwards the front legs come down (2–3). Scrapes occur in groups with a frequency of 5.7 Hz. Scrapes are broadband signals with peak frequencies at 230 Hz and 550 Hz. Production of seismic signal corresponds to movements of the abdomen.
Buzz signal: Front legs come down (1–2) as the abdomen oscillates at 65 Hz (1–2). This signal has a fundamental frequency at 65 Hz with several harmonic frequencies (130 Hz, 195 Hz and 260 Hz). Production of seismic signal corresponds with movements of the front legs and abdomen.
Elias et al. found that thumps came from the front legs impacting the ground, scrapes were produced by rubbing together a set of bristles between the head and body, and buzzes were made by the spider vibrating its body. They note that their research species (Habronattus dossenus) is the only species known to produce all three of these signals. It sounds like the spider in the video does all three of these so I guess that means it’s a H. dossenus.
In a follow up study, Elias, Hebets, Hoy and Mason investigated the results of muting the males by using wax to connect the spider’s head and body. They found females were more likely to mate and waited less time before mating with vibrating males. In addition, many of the muted males were eaten before getting a chance to mate.
I’m glad I finally tracked down the rest of the story (I hope). It turns out that some spiders bang their abdomens against the ground but the spider in the video is actually do a much more complex dance. Spider sure have some interesting mating patterns.
A. P. Noordam. 2002. Abdominal percussion and ventral scutum in male Euophrys frontalis (Araneae: Salticidae). Entomologische Berichten, Amsterdam. 62:17-19
A. L. Rypstra, C. Wieg, S. E. Walker & M. H. Persons. 2003. Mutual mate assessment in wolf spiders: differences in the cues used by males and females. Ethology. 109:315-325
D. O. Elias, A. C. Mason, W. P. Maddison & R. R. Hoy. 2005. Seismic signals in a courting male jumping spider (Araneae: Salticidae). Journal of Experimental Biology, 206:4029-4039
D. O. Elias, E. A. Hebets, R. R. Hoy & A. C. Mason. 2005. Seismic signals are crucial for male mating success in a visual specialist jumping spider (Araneae: Salticidae). Animal Behaviour. 69:931–938
Thanks to Harley for showing me the video