How dung beetles keep cool
Posted: Wed Oct 24, 2012 7:25 am
this article from the Star newspaper of 23 October.
"First it was the dung ball boogie. Now scientists believe dung beetles are using their balls of poo to cool off.
The ball of dung, scientists believe, is like a soggy mobile air conditioning unit, 50 times its own weight, that the insect lugs across the sand.
This is something a combined team of South African and Swedish academics discovered after subjecting dung beetles to a battery of experiments that included using thermal imaging cameras and kitting them out with special lime green booties.
“We found that dung beetles climb onto their balls of dung they are rolling to cool off, before continuing on their way,” said Professor Marcus Byrne from Wits University.
The moist dung ball becomes a sort of mobile oasis that the insect can take temporary refuge on from the hot sands that can reach 60°C in the midday sun.
Not all dung beetles do this; only 10 percent of the thousands of species are what the scientists call rollers.
Earlier work by Byrne and his colleagues revealed that some beetles use their dung balls as a direction finder, and the stage for a unique dance.
As they roll the dung ball, beetles will often climb on top and do an “orientation dance” to establish the position of the sun. They do this, believes Byrne, to maintain a straight line and move away as quickly as possible from the pile of dung and the possibility of being robbed of the ball by other beetles.
It was about three years ago on a sweltering day, near Vryburg in the Northern Cape, when Byrne said they had a eureka moment. “We were getting hot – then we thought what about the beetles?” the professor said.
They noticed that when it was hot, the beetles climbed on top of their balls more often, but they had to prove it to science.
To do this, they conducted a series of experiments. The scientists got the insects to roll their dung over shaded and heated patches of ground. They snapped thermal imaging pictures of the beetles and their poo. They placed the balls of dung in the refrigerator. Then they turned to the lime green boots.
The researchers applied silicon boots to the front legs of the beetles. It is the front legs that come into direct contact with the hot sand as they push their balls of dung
The idea was that the boots would protect their legs from the heat. “They didn’t like it, but it worked, the beetles with the boots didn’t climb onto their ball as often,” said Dr Jochen Smolka, from Lund University in Sweden. They found that hot beetles climbed on their balls seven times as often as those crossing cooler ground.
Their findings appear in the latest issue of the academic journal Current Biology.
This was the first example of an insect using a mobile thermal refuge, said Byrne."
, will be observing these little critters in a different way now.
