Paneth cells

turned out, these beetles were not only active for most of the day (and night), but also showed an extremely robust and easily manipulated orientation behaviour. As soon as these strong insects are in the possession of a dung ball, they will unconditionally and immediately transport this package of food along a given course until they reach soft and easily manipulated ground. Here, they dig down and feed on their take-away meal in underground security. To support this straight-line travel over the African Savannah, the beetles are guided by a compass that is so sensitive that they can rely on the dim polarization pattern around the moon, or even the Milky Way for orientation, an achievement that is so far unequalled in the animal kingdom. In contrast to other insects, we also find that the dung beetles rely exclusively on cues from the sky for orientation. This makes it possible to evaluate the function of their celestial compass without the confounding influences of, among other things, landmarks. The large body and brain size of our current model species further make them ideal for neurophysiological recordings and the attachment of more or less sophisticated pieces of scientific equipment. In addition to caps, we have placed little silicone boots on their feet, made them roll frozen scoops of dung and tracked them over tennis courts and hockey pitches. People often wonder if our beetles can be made to roll a golf ball, and yes indeed, this works as well. Dung beetles are ideal model animals to investigate a highly-sensitive sky-compass navigation system, from neurons to behaviour, in one single species. Revealing the principles underlying this simple straight-line orientation system is an important step towards understanding more complex navigation, such as that employed when returning to a nest or food source.