In the African savannah can reach 149° Fahrenheit in the middle of the day, which leads to burning sand and an obvious problem for anything that lives there, including small insects that spend their lives on the surface of the sand. Some insects seek protection in the shade or climb up blades of grass to escape the worst of the heat.
But South African dung beetles have come up with a unique strategy to escape the heat of the sun; they climb on top of their rolled-up meal, which happens to be a ball of dung. These dung balls are a kind of air conditioning unit because the ball is made from the moist dung of a large(ish) mammal. When the moisture in the dung ball evaporates in the heat, the ball is cooled down.
How did researchers from Lund University in Sweden discover this? By the only thing more interesting than dung air conditioning - they put small silicon boots on the beetles’ front legs.
The dung beetle’s main interest in the dung ball is to eat it, but the beetle has also worked out how to cool down on top of the ball. The Lund researchers have been able to prove this by studying the dung beetles’ behavior in different experiments. Dung beetles on hot sand were seven times more likely to climb up onto their ball than dung beetles that rolled their balls on cooler sand.
In another experiment, the researchers put a type of silicon boot on the front legs of a number of dung beetles to protect their feet from the heat. The results showed that dung beetles with silicon boots did not climb up onto their balls as often.
“Our study shows that insects employ sophisticated methods to regulate their body temperature. Evolution has an incredible ability to utilise existing materials for new functions”, says Jochen Smolka, a researcher at the Department of Biology at Lund University, who has carried out the research with colleagues from Lund and other researchers from South Africa.
Not all species of dung beetle roll their meals away in the form of dung balls; only around ten per cent demonstrate such behavior. The reason they roll the balls away from the pile of dung is to be able to eat in peace, without competition from other beetles.
Citation: Dung beetles use their dung ball as a mobile thermal refuge. Jochen Smolka, Emily Baird, Marcus J. Byrne, Basil el Jundi, Eric J. Warrant and Marie Dacke, Current Biology, Volume 22, Issue 20, R863-R864, 23 October 2012
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