Dung Beetles are Dancing with the Stars

    
Scarabaeus satyrus

Photo credit: sky-news.com

Scientists at the Wits University of South Africa and the Lund University in Sweden have recently published findings that dung beetles make use of the Milky Way to navigate their dung rolling routes!

Of the three groups of dung beetles, this particular beetle is known as a roller, rolling dung in rounded balls which are either used as a source of food or as a breeding chamber. In South Africa there are about 6000 species of dung beetles, of which about 800 are rollers. Only 10% of these roll during night time, says Marcus Byrne, a professor of zoology and entomology at Wits University. What is particularly important to this beetle, known as the “Scarabaeus satyrus”, is that they roll their dung ball to an outlying spot, away from anywhere their rivals can get hold of the precious stash on which they have worked so hard to perfectly mold. Other dung beetles; the tunnelers bury dung whenever they find it, and the dwellers simply just live in it.

One should not turn up one’s nose at these beetles for rolling and burrowing dung. This fascinating beetle is the first insect species – not to mention animal -that is able to orientate itself by making use of the galaxy. It might not be the brightest bulb or have the sharpest eyesight, but the dung beetle has proven to make use of the progressive gradient of light  from the Milky Way to assist them in rolling their dung balls in a straight line. By using the celestial body as a ‘light compass’, dung beetles roll their balls of muck away from the point of creation and thus avoid rolling it back in a circle to where their competitors are able to nab their cherished ball.

What’s more, these beetles crawl on top of their dung globe and then perform a ‘dance’ of some sort. They position themselves on their vertical axis on top of the ball, in search of the best sources of light for their path orientation.

South African scientist Dr. Dacke has shown that these beetles are able to keep a straight line by making use of signals from the sun, moon as well as the pattern of polarised light formed around these light bases, as opposed to artificial sources. An experiment was performed by Dr. Byrne and the team to determine whether in fact it is the light source from the Milky Way that resulted in these beetles following the gradient of light. They simulated a starry night sky at the Wits planetarium and the outcome proved just that! The galaxy is so far away, that from the dung beetles’ viewpoint it is static and therefore provides a set point from which to roll their dung balls.

Dr. Dackes’ experiment further proved that a diffuse bar of light also helped these beetles on their way, which indicates that it is the bar more than the points of light that is important. Further research is now underway to establish which other elements assist the dung beetle in drawing its tight and narrow course.

Not only are these beetles intriguing but they also play an important role in the eco system. They perform the essential – albeit unpleasant – task of breaking up, disbanding and burying dung. As Dr. Byrne puts it, “Dung beetles are such co-operative animals. You don’t have to train them or coax them. Give them poo and they behave.”

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