Scientific research is worth doing for the same reasons that art and creative writing are worth doing; because it is interesting and it answers worthwhile questions. It is also, says Professor Marcus Byrne from the Department of Animal, Plant and Environmental Sciences at Wits University, fun.
Speaking at Duerden Lecture, held annually to honour the first Head of the Department of Zoology and Entomology at Rhodes, Professor Byrne described himself as “a man who has spent a lot of his life working with small creatures who live in poo.”
The small creatures in question are dung beetles, of which there are 800 species living in South Africa. They make use of the vast amounts of dung deposited by both stock animals such as cows and sheep, and wild animals, including elephant, buffalo and kudu among others. Without these little beetles, we would be in considerably unpleasant circumstances with regard to the level of animal waste around us.
Here in the Eastern Cape, Professor Byrne acknowledged during his lecture, we have an amazing sub-species, the Circellium bacchus or Addo flightless dung beetle, one of the rarest species of dung beetle due to its restricted and isolated population, its habitat specialization and its co-evolution with, and dependence on, falling numbers of large wild mammals, namely the elephant and the Cape Buffalo.
Not all species roll a ball of dung, preferring instead to burrow down into it, creating a network of tunnels. Researchers speculate that the creation of a ball which can be rolled away is an adaption which became necessary due to the overcrowding the tunnel system creates. And why is the dung ball so important?
Firstly, the beetles eat the dung. Secondly, they lay eggs in it and thirdly, certain species give it as a nuptial gift, having used it to lure their intended mate to a prepared burrow. The entire life cycle of the beetle takes place in dung, a metamorphosis from egg to grub to beetle, and the content of the dung ball the mother has crafted shapes the success of her offspring. Those that do roll balls are very good at it, due to a tendency of the male beetles to fight each other for possession.
Dung beetles rolling their balls maintain a remarkably straight path, often climbing up onto the ball and performing a 360 degree ‘dance’ before getting down and setting off again in the classic ‘head down, back legs up’ posture.
In a series of experiments researchers showed that dung beetles have a superb ability to navigate using a light intensity gradient, while moonless and starless nights, and heavily overcast days, confuse them. Beetles also utilize the fact that light is polarized. The dancing behavior allows them to reorient themselves and is so successful that even when interrupted the beetle is able to recover and continue on a virtually unchanged course. Preening behavior noted during the dance would appear to serve a thermological function, allowing the beetle to cool down when travelling through hot sand.
Photo and story by Jeannie McKeown.
Photo: Professor Marcus Byrne from the Department of Animal, Plant and Environmental Sciences at Wits University.