Why Did the Beetle Cross the Road?

That’s what I would like to know.  On Saturday I walked the dog around the neighborhood much later than I usually do, around noon.  And although a scan of the skies turned up only the usual vultures, a scan of the road was far more productive.  It seemed everywhere, there were ground beetles crossing the blacktop.  These can be fast moving beetles, usually found scuttling from under the mulch or under a rock, but here they were, in several places, some sauntering, some zipping, and some raising up on higher legs to miss hitting a pebble on the road.  We had had rain a day earlier, and it was one of our coolest days yet; first day of fall for that matter.   Why not take a brisk walk on such a lovely day?

But then, a neighbor asked if I wanted to walk with her, so, no sooner had I got home than we went back around.  I wanted to get a closer look at exactly which species of ground beetle this might be, when what did we see?  What looked like a dung beetle festival!  Coming around a bend the road was alive with lots of dung beetles “on a roll”, rolling their dung ahead of them as though they were in a race. Wow!!

Now nothing is more entertaining to watch than a bunch of dung beetles racing across the road, pushing, balancing, sometimes from a forward position, sometimes from a backward position, some going it alone, some in pairs. 

 Well, there probably are some things more entertaining, but if you set your bar low enough, then this can be a riot to watch.  Why so many? Why now?  Again, it had just rained, an unusual event in TX and here in our neighborhood the reigning scat is deer scat, but in normal conditions it gets hard pretty fast, and is elliptical in shape.  These beetles were all pushing a very rounded, larger than originally produced, deer scat ahead of it. I can imagine that if you wanted to shape these scats into nice round balls, than after a rain would be the best time. 

On the remote chance that you aren’t up to speed on your dung beetle facts let me provide you with a few.  They are found on every continent except Antarctica; there are thousands of different species that they divide up into rollers, tunnelers and dwellers, depending on how they access the dung in question.  Only 10% are rollers but they are the ones you are most likely to see, and that was clearly the kind I was seeing.  “Rollers” go to the site and forms their balls that they can push either standing on their head or forward and they are in a hurry to roll it away from the competition.  If two seem to be working cooperatively, you are seeing a male and female getting their “nursery” ready. They will roll it into their underground tunnel and lay the eggs right in it, where the larvae will feed on it as they grow and pupate within it and then emerge as adults. 

 But seeing two can also be the scene of a “snatch and grab” as one beetle bumps off the other and makes off with the stash! 

If you really are looking to fill the vacant hours in a day, check out the amazing video on TED.com “The dance of the dung beetle” and you will find out that they roll those balls in a straight line, using the sun as a guide by day and polarized light from the stars by night!  And all this with a brain the size of a rice grain!

The other thing they studied was why they do this little dance on top of the ball on occasion.  Crossing a hot stretch of sand, a hot road or whatever they are looking to cool their little hot feet, and they also think they are visually orienting themselves.  Wouldn’t I love to get paid to run experiments like these!

So why did the beetle cross the road?  Well, in the case of dung beetle, to get to his home with the goods as quick as he could.  The ground beetles; the jury is still out.