Thursday, May 15, 2014

Did You Know That...Dung Beetles Use the Milky Way to Orientate?

Dung beetles, as only few people know, have remarkable navigation abilities, despite the relatively small sizes of their brains. It seems also that after dung beetles collect the dung (the most common characteristic of these animals), they do a little dance on top of it before moving it in a straight line to their final destination. The dancing actually helps the dung beetle get its bearings as it dances around in circles, looking at the stars.
This behaviour, as well as the fact that dung beetles have specialized eyes which analyse the direction of light polarization, first led researchers to affirm that the beetles might be using the sky to orientate. During the day, it was easy to see that they were using this polarized light found around the sun in order to navigate. But nowadays it wasn't exactly known how they manage to navigate at night. This have led scientists to say they might be using the moon.
To test this, there are a variety of different experiments conducted by Marie Dacke, a researcher of the Lunds University in Sweden. She and her scientific crew set up a circular arena with high walls in South Africa, blocking out views of everything but the sky. They then timed a particular specie of dung beetle (Scarabaeus satyrus) on how long they took to cross the arena. The beetles were tested in different conditions: with the moon out, without the moon, and with an overcast sky. To harden the situation, some of the beetles were also equipped with caps, which forced their eyes downward, so they weren’t able to see the sky at all under any conditions.
They found out that dung beetles had a tough time staying in a straight line when there were clouds obscuring the sky and when they were wearing the caps. However, when there was a clear sky with no moon, the beetles were still able to orientate. This led to the idea that they use stars to navigate during the night. But, as Dacke said, “We thought that they could be using the stars, but dung beetles have such small eyes that they don’t have the resolution, or sensitivity, to see individual stars". This is actually a real issue to demonstrate !

To study this further in order to ensure the results, the researchers repeated the experiments under strict conditions. They moved the arena to a planetarium where they were able to control stars locations and movements. Once again, some of the beetles wore caps (as you can see in the photo on the right). This time, they showed the beetles the brightest stars, showed only the Milky Way, and then showed the entire sky. What they found is astonishing: the beetles were slow to cross the arena when the brightest stars were visible, but they crossed at normal speed when only the Milky Way was visible. As the first attempt, beetles with caps had lots of problems orientating.
The conclusion is that beetles use the Milky Way in order to navigate. This falls in line with the findings of a similar experiment that used the Scarabaeus zambesianusa, a different type of dung beetle, which was unable to move in a straight line without the Milky Way in the sky.
The ability to roll a ball of dung in a straight line is very important for the survival of these insects. After they create a ball of dung, they have to roll it away as quickly as possible to avoid having it stolen by others of its specie. They don’t have time to wander around! They have to get out of there fast. Once the pile of dung is a safe distance away, the dung beetle will bury it and it becomes food for the beetle’s offspring.
And, talking about speed, we don't have to think this insect isn't strong. In fact it can be considered a superbug: with its own strength it can push 1.141 times its weight. Pretty powerful...
And now let's see these dung bettles "rollin", if you know what I mean...

2 comments:

  1. Oooh, interesting. Who would have thought dung beetles know the milky way better than some human. Another amazing fact! Bravo!

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    Replies
    1. Pretty great, isn't it ? When I first heard of it I was shocked. We have lots of things to learn from animals...

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