Simple, they look up to the sky, because the answer is written in the stars
You may recall from a previous post that us dung beetles use the sun’s polarization to guide us in a straight line back home. Like many other insects, we have photoreceptorsthat enable us to see the polarisation. Well, at night we use the moon’s polarisation, rather than the sun.
But what happens when the moon is hiding?
As you would expect, the dung beetle just gets on with it. A research team noticed that hard working night shift dung beetles were still busy rolling (in straight lines home, not wandering around aimlessly) even when the moon was no where to be seen.
So, in a cunning plan, the scientists devised yet another experiment for us dung beetles to tackle (and as usual, we did not disappoint)
This experiment involved placing an unsuspecting dung beetle and its prized dung ball in a large inverted circular drum. This stopped the beetles from seeing anything land based.
One by one, they placed beetle after beetle into the drum and observed the following:
with the full moon shining, it took about 20 seconds to reach the edge
with a starry night and obscured moon, it took about 40 seconds
and with no moon or stars (they had to place a hat on the poor dung beetle!), it took a whopping 2 minutes
So, now we know why you never see a dung beetle wearing a hat while working (it just makes work 6 times harder)
But what else did the scientists figure out? The experiment demonstrated that the moon’s polarisation offered one form of navigation, but that the ‘line’of the Milky Way stars offered an alternate navigation source, when the moon was nowhere to be seen. Although dung beetles have ‘simple’ eyes and cannot see individual stars, they can see the sparklingline of the beautiful stars within the Milky Way.
References: To my surprise two research teams have undertaken similar research studies into dung beetle night rolling. This article by New Scientist and The New Yorker were particularly well written. Would rather watch than read? Check out this DNews report – not surprisingly, it comes with some ‘poo’ jokes.
it helps cool our feet from the hot sands of Africa and
it helps us find our way back home
To cool your feet…
‘Put your left foot in (to the dung ball), put your left foot out. Put your left foot in and shake it all about.’
You see, freshly laid dung is about 30C°. When comparing the air temperature, which can easily reach about 50C°, with the sand temperature, which can easily hit 60C°, the dung ball readily becomes a refreshing slipper to cool your feet in.
Once cool enough, you can get back to your mission.
To find your way home…
‘You do the hokey pokey and you turn around. That’s what its all about.’
We use the sun as our guide to find our way back. Many insects, including us mighty dung beetles, can see the sun’s polarisation as the rays hit the earth. They become our map, providing a nice straight line for us to use as a path to find our way home.
If we get distracted along the way (eg: another dung beetle taking a shining to your dung ball and before you know it, you find yourself in a Dr Seuss version of a dung beetle battle) all we need to do to get back on course, is to jump up onto our dung (provided we didn’t lose the battle)! We get a great view of the sky and this helps us find a straight line back home to our burrow.
Instead of the daily roll, I thought I’d start the day with a spot of fishing.
It was quite satisfying and very relaxing in comparison.
But did you know that I’m not the only dung beetle keen to expand on my daily dung intake with some more, let’s call it exotic dung.
A recent research project lead by Sean Whippie and Wayatt Hoback involved the team catching various dung beetle species to see which dung they preferred (the beetles that is, not the researchers). A series of pitfall traps were set up with a variety of dung delights – all you could eat herbivore, omnivore and carnivore dung, including exotic human, chimpanzee zebra, donkey, moose and waterbuck. (I wonder who volunteered for the human samples?)
Surprisingly to the human researchers (but not me), the dung beetles were particularly fond of exotic dung and showed little interest for their local dung source found in ample supply on the great plains of the North America – the bison.
After two years of playing with dung and capturing over 9,000 dung beetles, the data indicated that of the omnivore samples provided, human and chimpanzee were top of the favourites list.