Friday, September 28, 2007

Size Matters When it Comes to Practicing Safer Sex

A research team based in New Zealand and Kenya have found that in the East African jumping spider, Evarcha culicivora, the size of their mate matters to them. A study recently published in the scientific journal, Ethology, found that despite the risk of sexual cannibalism, virgin females were attracted to bigger, meatier males. The female spiders will choose the larger males to first breed with them for the sole purpose of mating. Yet after experience, these female would opt for the smaller mate, resulting in “safer sex.”

More often than not the female Evarcha culicivora is larger than her mate. Large males tend to be more caniballistic towards smaller females, which has led to the evolution of the females’ mate choice behavior. If Evarcha culicivora females could choose their mates by preference, they prefer the larger males, although that is not the safest choice. In order to make sure that these female mating choices were based on size alone and not courtship behavior, Dr. Pollard explained in his study that these jumping spiders native to East Africa have exceptional eyesight in comparison to other animals of their size. Due to the fact that these spiders have such good eyesight, they tested virgin females- that were bred in a lab- with non virgin males. Using different sized dead males arranged in lifelike positions the study resulted in females that were more than two times likely to choose the larger mate. Yet, two our of three females that had copulated, chose the smaller mate. They also tested this exact same experiment with live spiders and the results came in the same. I guess size really does matter to these female Evarcha culicivora when practicing safer sex.

Source:
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1439-0310.2007.01394.x
(In order to access this link, you have to have a subscription to the journal. I made a request to the UMASS library to get a subscription in order for everyone to check out the online journal.)

Posted by Kayla Carrero (1).

6 Comments:

At 6:17 PM, Anonymous King-Emily said...

Kayla,
I thought this was a really interesting article. The title was a great attention grabber. Also the use of the term "safer sex" at the end of the first paragraph really drew me in and made me want to keep reading. Your writing style was clear and articulate. Great job!

 
At 10:13 PM, Blogger PWH said...

This topic is very interesting. You did a great job presenting the information in an organized manner. However, I would like to suggest a few things that need clarification.

1. You mentioned that "female spiders needed to get the bigger males out of their system". Could you elaborate on that? If there is a risk of cannabalism to occur during or after the copulation, why can't the female spiders just settle for the smaller males? What is it about the bigger males that the female spiders are so attracted to? Is it a more (supposedly) seductive chemical or pheromone, like the guy deodorant Axe? Or is it just better sex?


2. How were researchers able to determine which female spiders were virgins? Did they breed them in captivity?

3. And lastly, towards the end of your blog you mentioned that "two out of three females that had copulated chose the smaller males". Was that during the experiment or from their own observations outside of the experiment? I was under the impression that the virgin female spiders were being presented with dead non-virgin male spiders...

Could you please post the link to the article too?

Posted by Luzviminda Maurillo

 
At 10:23 PM, Anonymous Anonymous said...

This is an interesting topic. It seems strange though that the females learn to choose smaller mates with more experience. You would think that if they survived the first time that they wouldnt learn the true danger of a larger mate. I wonder how they learn the risk of mating with a larger male if they dont truely experience the higher rate of cannabalism in larger males.

Posted By Hollis Martin (1)

 
At 10:24 PM, Anonymous Anonymous said...

This is an interesting topic. It seems strange though that the females learn to choose smaller mates with more experience. You would think that if they survived the first time that they wouldnt learn the true danger of a larger mate. I wonder how they learn the risk of mating with a larger male if they dont truely experience the higher rate of cannabalism in larger males.

Posted By Hollis Martin (1)

 
At 11:40 PM, Blogger PWH said...

This comment has been removed by the author.

 
At 11:41 PM, Blogger PWH said...

It seems as if the spiders were indeed bred for the sole purpose of the experiment and was found to be virgins.

If the above is true, this means that the sexual preference to mate with larger males must be hereditary. When you metioned that the 'spiders needed to get the bigger males out of their system,' it was very unclear. What I understood it as was that the female spiders will choose the larger males to first breed with them for the sole purpose of mating. Then they will copulate with a smaller male just to eat them.

I tried to read the article itself but it won't let me for some reason... I wish you can clarify it a bit more.

Eun Shin (1)

 

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