/ 23 October 2012

Dung beetles rolling to be cool

Researchers have found dung beetles use their dung balls to cool off in the heat.
Researchers have found dung beetles use their dung balls to cool off in the heat.

The roads of the Kruger National Park are littered with massive heaps of elephant dung. For the excited tourist these hold the promise of one of the lumbering giants around the next bend. Fingers hover over camera buttons and most miss the little black dung beetles scuttling off with huge lumps of dung.

We know that they roll up their ball of dung – some 50 times heavier than themselves – to get food away from competitors. But the work is hard, especially when temperatures are scorching and the sand burns. 

To get a bit of relief, researchers have found that the dung beetles climb on top of their ball to cool down. 

Professor Marcus Byrne, from Wits University, said that this only happened around midday, and only when the beetles were crossing hot ground.  

“We stumbled upon this behaviour by accident while watching for an ‘orientation dance’ which the beetles perform on top of their balls to work out where they’re going. We noticed that they climbed their balls much more often in the heat of the midday sun,” he said. 

To see if this behaviour was to cool their legs down, the research team applied silicone boots on the beetles front legs. Dr Jochen Smolka, from Lund University, said these cooled their feet down, and as a result the beetles rarely climbed onto the dung. 

While on top of the dung balls, the beetles also spread regurgitated liquid onto their legs and head to cool down a bit more. They do not do this at any other time of the day. 

The beetles have to resort to this behaviour because they are cold blooded – so they need to resort to different techniques to regulate their temperature, said Smolka. 

“Evolution has an astonishing ability to make use of existing structures for new purposes – in this case using a food resource for thermoregulation,” he said.