Dung beetles are beetles that feed partly or exclusively on dung. A dung beetle can bury dung 250 times heavier than itself in one night. Many dung beetles, known as rollers, roll dung into round balls, which are used as a food source or brooding chambers. 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. They are often attracted by the dung collected by burrowing owls. Dung Beetles can grow to 3 cm long and 2 cm wide.
All the species belong to the superfamily Scarabaeoidea; most of them to the subfamilies Scarabaeinae and Aphodiinae of the family Scarabaeidae(scarab beetles). As most species of Scarabaeinae feed exclusively on feces, that subfamily is often dubbed true dung beetles. There are dung-feeding beetles which belong to other families, such as the Geotrupidae (the earth-boring dung beetle). The Scarabaeinae alone comprises more than 5,000 species. Dung beetles are currently the only known non-human animal to navigate and orient themselves using the Milky Way.
Ecology and Behavior[]
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. One type living in Central America, Deltochilum valgum, is a carnivore preying upon millipedes. 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. 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,[13] 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, a form of mass provisioning. Some species do not leave after this stage, but remain to safeguard their offspring. The dung beetle goes through a complete metamorphosis. 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 behavior of the beetles was poorly misunderstood until the studies of Jean Henri Fabre in the late 19th century. For example, Fabre corrected the myth that a dung beetle would seek aid from other dung beetles when confronted by obstacles. By observation and experiment, he found the seeming helpers were in fact awaiting an opportunity to steal the roller's food source.
Benefits and Uses[]
Dung beetles play a remarkable role in agriculture. By burying and consuming dung, they improve nutrient recycling and soil structure. They also protect livestock, such as cattle, by removing the dung which, if left, could provide habitat for pests such as flies. Therefore, many countries have introduced the creatures for the benefit of animal husbandry. In developing countries, the beetles are especially important as an adjunct for improving standards of hygiene. The American Institute of Biological Sciences reports that dung beetles save the United States cattle industry an estimated US$380 million annually through burying above-ground livestock feces.
In Australia, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) commissioned the Australian Dung Beetle Project (1965–1985) which, led by George Bornemissza, sought to introduce species of dung beetles from South Africa and Europe. The successful introduction of 23 species was made, most notably Onthophagus gazella and Euoniticellus intermedius, which has resulted in improvement of the quality and fertility of Australian cattle pastures, along with a reduction in the population of pestilent bush flies by around 90 percent.
An application has been made by Landcare Research to import up to 11 species of dung beetle into New Zealand. As well as improving pasture soils the Dung Beetle Release Strategy Group say that it would result in a reduction in emissions of nitrous oxide (a greenhouse gas) from agriculture. There is, however, strong opposition from some at the University of Auckland, and a few others, based on the risks of the dung beetles acting as vectors of disease. There are public health researchers at the University of Auckland who agree with the current EPA risk assessment and indeed there are several Landcare programmes in Australia that involve schoolchildren collecting dung beetles.
Like many other insects, the (dried) dung beetle, called qianglang (蜣蜋) in Chinese, is used in Chinese herbal medicine. It is recorded in the "Insect section" (蟲部) of the Compendium of Materia Medica, where it is recommended for the cure of 10 diseases.
In Isan, Northeastern Thailand, the local people famously eat many different kinds of insects including the dung beetle. There is an Isan song กุดจี่หายไปใหน "Where did the Dung Beetle go", which relates the replacement of water buffalo with the "metal" buffalo, which doesn't provide the dung needed for the dung beetle. Hence, the increasing rarity of the dung beetle in the agricultural region.
