Dung Beetle Perspective
By Dave Rushworth
Many people have commented that we are seeing progressively less insect life recently. This perception, if correct, may be due to insecticide application for agricultural or health reasons or it may be due to the dry cycle we have experienced over the past few years.
There needs to be strict monitoring of poison applications and storage security of these substances particularly because the use of DDT and other such chemicals are still permitted in this part of the world. Legislation provides for very heavy penalties for the misuse and incorrect storage and handling of dangerous chemicals, which is affecting our birds and other animal life.
Despite dismal predictions, it is still a joy to see the activity of small animal life now that some rain has fallen in our area. The 'army ants' on their way to raid termite colonies, millipedes or 'Tshongololos' tracing the ground with their double-track spoor or the black ground beetles, with their white warning spots and erratic gait, searching for prey. The immature 'sand lizards' mimic these beetles, with hunched backs and gait, with great immunity from predators.
Undoubtedly, one of the most commonly noticed insect activities is that of the dung beetles, particularly those rolling dung balls. As it is such an interesting and well known subject let us use 'the dung beetle' to gain some perspective on our animal life. The animal kingdom is split, by zoologists, into a number of major divisions known as 'phyla'. The largest 'phylum' is the ARTHROPODA - that containing all the invertebrate animals with hard ecto-skeletons and jointed limbs.
The 'arthropoda', like other 'phyla' is divided into 'classes', one of which is the INSECTA (also known as Hexapoda, meaning six-legged). This feature distinguishes 'insects' from other classes of arthropods such as Diplopoda (millipedes), Chilopoda (centipedes) and Arachnida (spiders, scorpions and mites).
Insects are not only the largest group of animals, with a million or more species, but also the most successful. They inhabit every part of the world's environment. To complete our 'dung beetle' classification, the class 'insecta' is divided into 'sub-classes', where the beetles fall into 'PTERYGOTA' (winged) and then into 'divisions'. These 'divisions' are divided into 'orders' and the 'beetles' fall under the 'order' COLEOPTERA.
COLEOPTERA: 370 000 SPECIES
The Coleoptera is the largest and most diverse order in the entire animal kingdom. There are about 370 000 species throughout the world and we have around 18 000 species known from our region. This indicates that we are not particularly endowed with beetle species compared to some other parts of the world. It is still a great number. This number is divided into 'sub-orders', 'super families', then 'families', 'sub-families', 'genus' and finally 'species'.
Our 'dung beetles' fall into the family SCARABAEIDAE and then into the sub-family COPRINAE. There are around 8 000 species of what we call 'dung beetles', many of which we have in our region. Many of the most well known 'dung beetles', because of their habit of rolling dung balls, belong to the 'genus' SCARABAEUS. The familiar 'Rhino Beetles' belong to the sub-family Dynastinae and the well known ones to the genus Oryctes.
Of the hundreds of different species of 'dung beetle' our largest is the Heliocopris colossus, measuring up to 50 mm in length, while one of the smallest, Drepanoceros laticollis, is only around 5 mm. They all feed mainly on the dung of mammals.
In this area of the central lowveld, the most commonly encountered 'dung beetle' usually 'plops' in to surprise your guests at their evening meal. Attracted by the lights they are often seen at night. Rather smooth shelled, up to 20 mm in length and with a purple sheen, they leave a smell on your fingers if picked up. They are dung rollers, useful and harmless. They are one of the 'Plum Dung Beetles' - Anachalcos convexus -, which is found along the Limpopo valley and down the eastern border south to the eastern Cape.
Some of the well known species construct 'balls' which they roll away from competition and predation, to be buried as a food supply or on which they lay an egg. In the latter case the dung ball will supply food for the resulting larva, which will pupate and grow within the dung ball.
With many other species the dung is carried down below the main supply and buried in burrows. It is either used as a food supply for the adults or eggs are laid in the packed passages, where the young will develop as usual. Next time you have a chance to examine a pile of fresh animal dung, have a look for the various types of dung beetle.
You will be surprised how many small, concealed species of various colours there are working away. If you happen to pick one up, look underneath at the leg joints and under the 'neck area'. There are normally many, tiny 'mites' which are hitching a ride.
They climb aboard from one dropping and catch a lift on that 'aircraft' to the next dropping, where they disembark, while others take their turn. The interaction between species is endless and vital in maintaining natural systems.
Piles of animal dung and the 'workers' within form a most valuable source of food for many of our lowveld animals. Many species of birds can be seen searching for insects and seeds. Mongooses and other insectivores often scratch for insect food. In the remote, dry parts of the Kalahari area, elephant droppings are the only source of food for many species that would otherwise be unable to live in those areas.
PICKING UP THE SCENT
Dung beetles are able to pick up the scent of any food source from a great distance. To do this they will quarter down wind, flying backwards and forwards across the wind until they pick up scent. Once the scent is located they will follow upwind direct to the source, where they 'plop' directly onto or near target. They will be quick to locate any fresh dung and can be a useful indicator of the proximity of large animals such as buffalo or elephant. They can be quite un-nerving to a 'squatter'.
In 'healthy' veld conditions, dung beetles will scatter a dung pile in very short time. In the dry season, when the insects are dormant, the dung is often left untouched. This can become an indicator of dry or wet season droppings when assessing the history of an area. Unbroken buffalo and other droppings sitting for years on the soil surface are an indicator of serious soil problems and bad veld conditions. Like all animals, the beetles require moisture, air and food. Without one of these they will perish. Their presence or absence is a valuable veld condition indicator, apart from being an interesting attraction.