How dung beetles make light work of poo
Johannesburg - They are the white lab rats of the insect world, only better – and that is what keeps a group of scientists coming back to North West year after year.
What the scientists come to study are dung beetles – and in this remote corner of the province, 70km north of Vryburg, there are lots of them.
And the reason there are so many of them is that this is cattle country – and cows drop loads of poop.
While researchers like dung beetles because they are so predictable – dung beetles do what they do, they roll dung – these curious critters are also quite puzzling, says Professor Marcus Byrne of the Wits School of Animal, Plant and Environmental Studies.
Take the mother dung beetle.
Dung beetles are one of the few insect species to care for their young.
The mother beetle carefully lays one egg at a time in a so-called brood ball of dung.
Tests of these brood balls have indicated high concentrations of nitrogen – much higher than the pile from where the ball originated.
“How the hell they do that, sorting out the nitrogen – it is something we need to find out,” says Byrne.
Then there is that whole issue of mother-child bonding that takes place through the walls of a dung ball.
For three months, the mother dung beetle remains with the ball, and recordings appear to show that she makes sounds – perhaps calling to her young.
What she is doing and what she is saying is something that scientists for the moment can only guess.
“What they suspect is that she is communicating with her offspring, to ensure that the offspring are still alive and she should still hang around,” Byrne says.
These beetles don’t get fazed by anything – not even human handling.
Scientists like that too.
“Sometimes (animals) get scared. But not dung beetles,” says Dr Emily Baird of the University of Lund, Sweden.
These beetles skrik vir niks, and their behaviour in the field is how they will act in the lab, say the experts.
Over the past 10 years, Byrne and his colleagues from Lund University have been trying to unravel some of the beetle’s mysteries.
Here and there they have been successful.
Their latest discovery – which appeared in the journal Current Biology, and which The Star featured recently – has revealed that the dung beetle uses the Milky Way to navigate.
This adds to a list of other “sky compass cues” like the sun, the moon and polarised light that the beetle can draw on to maintain a straight path while heading out with his ball of poo from the dung pile.
But as one mystery falls away, others emerge.
There are more than 800 dung beetle species out there, and some have other interesting navigational aids that scientists are still trying to get a handle on.
In Namibia, a species of desert dung beetle appears to have a built-in pedometer.
This insect, scientists believe, finds its way back to its nest by counting its steps, and back-tracking.
But these are mysteries for future field trips, in a land with loads of cow poop and a beetle that isn’t bothered by much. - The Star