23 October 2012

Dung Beetles Use Dung As A Mobile Thermal Refuge For Thermoregulation

Dung beetles are also called scarab beetles. These are the same beetles worshiped by the ancient Egyptians. They believed that a giant dung beetle rolled the Sun across the sky and buried it at night.

They probably got the idea from observing that these beetles roll balls of manure across the plain and bury it under the ground. Dung beetles do this since they use these balls of dung for food or as a brooding ball where the female beetle will lay its eggs inside it. When the larvae hatches, they feed on the dung.

There are some dung beetles that feed on mushrooms, leaves, and fruits. Dung beetles that solely rely on dung as its food source, do not need to drink or eat anything else since all the nutrients are provided for by the dung.

Dung beetles have sensitive sense of smell. It is this heightened sense that enables them to track down manure.

These insects contribute greatly to the ecological balance of the land. They bury and consume dung which aerates the soil and help bring nutrients into it. It also controls the fly population since dung provides habitat for it and other pests.

Beetles use dung balls to stay cool

Dung beetles roll the balls of dung away to avoid it from being stolen by others. The beetle can roll a ball weighing fifty times heavier than its own weight.

Aside from rolling the ball to safety, scientists have discovered that these dung beetles also use the balls to keep cool and maintain body temperature.

"The beetles climb on top of their moist balls whenever their front legs and heads overheat," said Prof. Marcus Byrne from Wits University. "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."

Video: The Dung Beetle

They have noted that the beetles climb the balls seven times more often when the ground is hot compared to when it is cooler. After applying silicone boots to the front legs of the bugs (see image above), as a form of heat protection, the scientists noticed that the bugs climbed the balls less often.

The discovery marks the first example of an insect using a mobile thermal refuge in this way. It is also a demonstration of the remarkably sophisticated strategies that insects and other cold-blooded creatures employ to maintain their body temperatures.

Once on top of a ball at midday, the beetles were often seen "wiping their faces",The team also suspect that the bugs spread regurgitated liquid onto its legs and head to further cool down. This behavior is only observed during that time of day.

The findings are yet another reminder of the many creative solutions found in nature. According to Dr Jochen Smolka from Lund University, "Evolution has an astonishing ability to make use of existing structures for new purposes – in this case using a food resource for thermoregulation."


University of the Witwatersrand
Lund University
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