Dung Beetles: Looking to the Stars!

This is from a couple of days ago, but I only just saw it and thought this is worthy of some words!

Nice Hat…

So, a group of scientists from The Universities of Lund (Sweden), of the Witwatersrand (South Africa) and Pretoria (South Africa), have been dressing dung beatles in, what can only be described as little bonnets, in the name of scientific understanding! Though, the authors of the paper, published in Current Biology, refer to them as “small caps”.

Why am I wearing a hat?! How cute is this little bugger!
Of course, the study wasn’t just a fashion show (in my mind only!) for the wonderful dung beetle. Dr. Marie Dacke, the lead author, had already established that dung beetles were able to keep a straight line by using light from the Sun, reflected light from the Moon and even the polarised light that forms around them.

Being able to navigate in straight lines is important for the dung beetle. Once they’ve sourced dung and rolled it into a ball, they like to get as far away as possible from other dung beetles, who are more than happy to steal a good ball from one another. In the wild they prefer to find an underground lair before feasting!

An Exclusive Club!

As often occurs though, the sun and moon aren’t always available for guidance. This had intrigued Dr. Dacke, who had observed the beetles still successfully navigating on moonless nights and sunless days. She and her team devised a quite splendid way of controlling the starlight variables by bring the dung beetles in to the local planetarium, in Johannesburg.

Having already observed and studied the beetles in the field, using the small “caps” to occlude their view, the same methodology was employed indoors. A 3 meter diameter black circle was placed on the ground and the beetles were timed, upon leaving the 30 centimetre centre holding circle, until making it out of the 3 meter area.

The graph below shows the average time it took for the dung beetles to leave area, both indoors and out, during different celestial conditions.

As you can see a moonlit sky was the most effective method of guidance. What was new to this study, something that had only previously been shown in humans, seals and birds, was the ability to use the stars for guidance. This is the first time any insect has been shown to do this. In fact the study went much further, showing that the mighty dung beetle can use the light from just the plane of the Milky Way to navigate away to the edge of the arena.

This is really cool science! The investigation, as with nearly all such undertakings, was due to the curiosity of the scientists involved. We now know something new and exciting about the dung beetle, that may also apply to other insects.

I’m not going to go on about how cool I think this! I love a good nature study, me! I thought it might be worth going into a bit more detail about the small cap the dung beetles had attached to their thoraxes. The caps were only used in the field as, of course, the conditions could be fully controlled inside the planetarium.

The scientists were able to track and plot the paths the dung beetles took. Below are the plotted paths showing the dung beetles’ progress under a starry sky (A) and while wearing the cap (B).

Go home dung beetles, you're drunk!!
This clearly demonstrated that the dung beetles needed a view of the sky for navigation and that landmarks in their surrounding were not used as a preference. Very cool!

Ig Nobel Worthy?

I think what we can all take away from this is that, dung beetles that wear caps become useless, unproductive members of their society. Another quality the dung beetle can now claim to share with humanity!

This study made me laugh for two reasons. Firstly, because the caps just made laugh! Although its a practical solution and not the first time they’ve been used, they look funny. Secondly, look at the paths taken in figure B! The poor blighters didn’t have a clue what to do, with one of the beetles never actually making it to the edge.

This study also made me think. It’s always fascinating to discover a new quality in such a well know insect and such a (at the moment) rare one.

I have a bizarre image in my head of a dung beetle captaining a boat, using a sextant for navigation…

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