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Males Can Sniff Out A Well Fed Female July 8, 2011

Posted by Mrs Weird Scientist in Animals, Brain Power, Insects, Think About It.
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11 comments

If they’re a male black widow spider, that is. Simply by taking a little saunter across the female’s web, a male black widow can sense if a female is hungry or not. Why does it matter? Because female black widow spiders have a rather freaky habit of eating the male after mating. It’s how they earned their dangerous name.

Now that’s one massive female black widow spider. You would almost think she’s been doing some seriously heavy weights at the gym. But nope, females are normally much bigger than males. Those males best watch out!

The Smell Of Safety

Males have developed this very useful technique, which tells them whether or not a female has recently eaten. But if a female is hungry, she would be more likely to cannibalize the male spider. They take a sniff of those silk strands and then decide if they want to proceed or scurry away. A new study discovered this interesting skill and published the findings in the journal Animal Behaviour. So, how do researchers actually go about testing something like this?

Feeding Time For The Ladies

First things first. The researchers fed a bunch of hungry female back widow spiders. Using a cricket neatly held between forceps, they rested it on the web and waited for the female to come over, wrap the cricket in silk and chow down. The females got one cricket each week. Yet, by the time the fourth week came around, they weren’t so hungry anymore and didn’t really want to eat the crickets.

I bet this female black widow spider is thinking: “Ah, the satisfaction from a good meal of crickets. I think I’ll accept the advances of the male spider perched nearby. Since I’m well fed, I probably won’t eat him after we’re done.”

Another bunch of female black widow spiders were starved for a few weeks. It apparently didn’t put their lives at risk, but they did get a bit smaller. Now, let’s find out what happened when a male was placed on the web of a well fed or a starved spider.

One Step, Two Step, Three Step…Four

Since the male spiders can pick up scents with their feet, they were able to figure out the difference from one female to another just by walking on the web. Normally, a male black widow spider has a special dance he does to court the female.

In this experiment, the males danced far more actively on the webs of well fed females. Smart dudes! If anything, dancing and mating would leave them ready to eat – not be eaten! Typically, they dance around for an hour or two, which sure shows their dedication to the purpose. They wave their legs and pluck and tap at the web in a unique way, so that unlike prey they show the female they are interested to mate rather than become dinner.

If Only I Had Such Powers

Now I have a strong sense of smell but definitely nothing like these male black widow spiders. It’s too bad because I’m really scared of spiders even though I know most are harmless. If I had my way, I’d be able to simply smell any spider from several meters away. That would give my timid self enough time to run!