Wednesday, March 28, 2012

Sex, Lies and Spider Silk

Are you trying to get the girl, but you’re too cheap to get her a nice gift? You could take a page out of the nursery web spider’s Guide to Love and Sex.


WARNING: Do not date this nursery web spider. He's a jerk.
Photo from Wikimedia Commons by Mathias Krumbholz.

When a male of this species has his eye on a female, he will usually offer her a nuptial gift, which is typically a tasty prey insect nicely giftwrapped in spider silk. While the female is unwrapping her meal, the male has an opportunity to mate with her; That is, unless she discovers the meal is good enough to take the gift and run away. If this happens, the male will try to hold on to the gift and will often play dead, stretching out his legs and getting dragged by the female until she stops. At this point he will “revive” and resume mating with her. Surprise!




If that deceptive behavior weren’t obnoxious enough, researchers have discovered that males can also achieve mating success by giving crappy gifts, as long as they are well-wrapped (and concealed) in silk. In the wild, nearly 4 out of 10 wrapped gifts were found to contain nothing more than empty insect carcasses, which likely resulted from the male sucking out the nutritive-value of the prey item himself, and then giftwrapping the remaining trash for his gift. Brilliant, right guys? What a jerk, right girls?

But do the females fall for it?

Maria Albo, Gudrun Winther, Cristina Tuni, Søren Toft and Trine Bilde at Aarhus University in Denmark set out to see if the quality of the gift would affect whether or not a female mates, and if she does mate, how long she mates for. The research team went outside and collected a bunch of juvenile nursery web spiders, and then raised them up on a housefly diet until adulthood (This way the researchers knew that all the spiders were virgins, which is important). Then they offered males items to wrap: a normal housefly, a protein-enriched housefly, a worthless gift (a cotton ball, dry flower head or leftovers of a previously eaten fly), or nothing at all. They allowed each male to interact with a female for up to 30 minutes, and observed the female responses.

It turned out, females were equally likely to mate with males providing a normal gift, protein-enhanced gift, or worthless gift. But females were much less likely to mate with males that didn’t have any gift. So, to get sex, it was important to have a gift – any gift. The scientists also noted that males with worthless gifts did not play dead as often as males with quality gifts. That is probably because playing dead is a strategy males use when the female is trying to run away with the gift, and females didn’t try to run away with worthless gifts. Why bother?

Seems like a good strategy, doesn’t it? But be warned, fellas, a male may be able to get sex with a worthless gift, but that doesn’t mean good sex. Males that gave a worthless gift or no gift could not keep their pedipalps (their sperm-transferring bits) inserted as long as males that gave a normal or protein-enhanced gift.

What’s the moral to this spider-story? If you want to get the girl, it’s important to give her a gift. And if you want to hang on to her, you’re better off giving her a good gift. But unless your girl-of-interest is a spider or an entomologist, I don’t suggest giving her bugs.


Want to know more? Check this out:

Albo, M., Winther, G., Tuni, C., Toft, S., & Bilde, T. (2011). Worthless donations: male deception and female counter play in a nuptial gift-giving spider BMC Evolutionary Biology, 11 (1) DOI: 10.1186/1471-2148-11-329

5 comments:

  1. interesting how it does not matter whether the gift is good or bad as long as its given. also how the females don't run away from the males with crappy gifts as much as they do males with good gifts. its funny how the female does not care so much as to whats in the gift as long as its wrapped nicely.

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  2. I think that's really interesting too, Taylor! My suspicion is that the more the male wraps the gift, the longer it takes the female to discover whether it is good or bad. And the whole time she is unwrapping it, he is copulating with her. These females are a natural example of why not to give it up too soon.

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  3. Wow, this is the most interesting thing I've read all week! I think that also "It's the thought that counts"!

    Never realized how sneaky males in nature can be(besides myself..)

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  4. This discovery is fascinating, but its potential applications toward human courtship rituals is the real promise!

    To test these further applications, I shall gift my girlfriend a cornflake locked in a Rubik's cube, which in turn is concealed within the Lament Configuration, which is then in turn locked within a combination safe. While she attempts to get at the imagined riches within, I shall attempt copulation, and report back here with the results. If I do not return, assume me perished in the name of science!

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