Animal behaviours can sometimes jump out at you by their similarity to the kinds of things humans do. Most recently, I came across this video of golden orb-web spiders. Dominating the picture is a large speckled black and white female, confidently waiting for her next unsuspecting meal to arrive. What might not be so obvious is the weedy orange male, running scurrilously on her back. Not exactly a very human-like behaviour, I hear you say. Well, I answer back, you don’t know what he’s doing there.
What he is doing, is wrapping her body in the finest silks his body can produce. He is doing this because doing so makes the female a lot less aggressive, and much more likely to agree to mate. Just like the gift of a new dress – or more provocatively some sexy lingerie – the male hopes his actions will improve his chances in the bedroom.
Scientists call this behaviour (in spiders) mate binding. Spider silk contains chemicals which can be picked up by the female’s equivalent of a nose. Males actually start producing silk after already mating. The problem is, the males want to continue, but mostly the females want to stop. Females often get aggressive soon after, trying to force the unwanted male away. In extreme cases, the discarded male is sometimes eaten as a tasty post-coital snack. In an escalating war of generosity, the male lays down ream after ream of silk, which placates the female. The male then gets the chance to have his way again and again. Since females often mate with dozens of suitors, more sex means more chance of fathering the next generation of baby spiderlings.
Research published in Animal Behaviour showed that it wasn’t just the smell of the silk that was helping – it was the luxurious touch that was most important.
“No one had tested why and how the spiders do this. We tested whether chemical or tactile cues play a role in calming down females for remating,” said Li Daiqin, one of the researchers who studied this behaviour. “We found both chemical and tactile cues are essential but tactile sensation is more important. Thus we come up with the term ‘mate massaging’, which may be better ‘mate binding.’”
My thanks to Li Daiqin and his colleagues for providing the amazing video and photo.
Shichang Zhang, Matjaž Kuntner, & Daiqin Li (2011). Mate binding: male adaptation to sexual conflict in the golden orb-web spider (Nephilidae: Nephila pilipes) Animal Behaviour : doi:10.1016/j.anbehav.2011.09.010