Monday, 25 January 2016

The important role of the humble Dung Beetle in natural ecosystems

Dung beetles play a very important role in the health ant the fertility of natural grassland
Ancient Egyptians thought very highly of the dung beetle, believing that the dung beetle kept the Earth revolving like a giant ball of dung, linking the insect to Khepri, the Egyptian god of the rising sun.
Dung beetles belong to the family Scarabaeoidea; with most of the species being placed in the subfamilies Scarabaeinae and Aphodiinae (scarab beetles). Most species of Scarabaeinae feed exclusively on feces and are known as true dung beetles. There are dung-feeding beetles which belong to other families, such as the Geotrupidae (the earth-boring dung beetle). The subfamily Scarabaeinae alone has more than 5,000 species.

The dung beetles known as rollers, roll dung into round balls, which are used as a food source for their larvae to develop on are rolled and buried in brooding chambers that are dug into the ground. Others, known as tunnelers, bury the dung wherever they find it. A third group, the dwellers, neither roll nor burrow, they simply live in manure.

Spider Dung Beetle Sisyphus specie with dung ball
Dung beetles live in many habitats, including desert, farmland, forest, and grasslands. They do not prefer extremely cold or dry weather. They are found on all continents except Antarctica. They eat the dung of herbivores and omnivores, and prefer that produced by the former. Many of them also feed on mushrooms and decaying leaves and fruits. Those that eat dung do not need to eat or drink anything else, because the dung provides all the necessary nutrients. Most dung beetles search for dung using their sensitive sense of smell. Some smaller species simply attach themselves to the dung-providers to wait for the dung. After capturing the dung, a dung beetle rolls it, following a straight line despite all obstacles. Sometimes, dung beetles try to steal the dung ball from another beetle, so the dung beetles have to move rapidly away from a dung pile once they have rolled their ball to prevent it from being stolen. Dung beetles can roll up to 10 times their weight.
Male Onthophagus taurus beetles can pull 1,141 times their own body weight: the equivalent of an average person pulling six double-decker buses full of people. No wonder the dung beetle is known as one of the strongest animals for its size.

Spider Dung Beetle Sisyphus specie showing very long  hind legs
In 2003, researchers found one species of dung beetle the African Scarabaeus zambesianus navigates by using polarization patterns in moonlight. The discovery is the first proof any animal can use polarized moonlight for orientation. In 2013, a study was published revealing that dung beetles can navigate when only the Milky Way or clusters of bright stars are visible the only insect known to orient itself by the galaxy.

The "rollers" roll and bury a dung ball either for food storage or for making a brooding ball. In the latter case, two beetles, one male and one female, stay around the dung ball during the rolling process. Usually it is the male that rolls the ball, while the female hitch-hikes or simply follows behind. In some cases, the male and the female roll together. When a spot with soft soil is found, they stop and bury the ball, then mate underground. After the mating, both or one of them prepares the brooding ball. When the ball is finished, the female lays eggs inside it. Some species do not leave after this stage, but remain to safeguard their offspring. The larvae live in brood balls made with dung prepared by their parents. During the larval stage, the beetle feeds on the dung surrounding it. The dung beetle goes through a complete metamorphosis.

Dung beetles play a highly important role in the environment by taking animal dung that could spread various diseases amongst grazing animals and burry it in the root zone where it can be useful to the veld grasses, herbs, bacteria and fungi not leaving out the fertility and general health and structure of the soil. By burying and consuming dung, dung beetles improve nutrient recycling and soil structure simultaneously protecting domestic livestock, such as cattle goats and sheep as well as indigenous game from disease by removing the dung which, if left, could provide habitat for pests and diseases.
Most dung beetles specialize on the dung of particular animals, or types of animals, and will not touch the dung of other species.
Spider Dung Beetle Sisyphus specie sitting on top of dung ball
Sisyphus species - spider dung beetles
Small to medium beetles 3-12 mm black dark grey or brown hind legs very long move very energetically

Adults congregate to feed on fresh dung in particular the dung of small animals. They also feed on the dung of tortoises, birds, toads and large carnivores. The Sisyphus species form dung balls which they roll away to be buried approximately 50 mm below the surface. A single egg is laid in each ball. Sisyphus species are particularly active on hot humid days following rain. Like magic dung that has been dropped on the ground disappears due to the efforts of these highly energetic little creatures. In my case they are particularly attracted to the dung of my sheep in preference to goat dung.

Spider Dung Beetles Sisyphus specie rolling a dung ball 

Michael Hickman
Landscape Design and Rehabilitation Specialist


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