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Do dung beetles benefit or harm my pasture?

Answer:  The benefits of dung beetles to livestock and the pasture environment should outweigh any reservations we may have about their dietary choices. In addition to aiding in the processing of manure on the soil surface, beetles also help to reduce survival rates of ruminant-parasitic nematodes and flies. For example, manure is the breeding ground and incubator for horn flies (Haematobia irritans) and face flies (Musca autumnalis), two economically important pests of cattle. A single manure pat can generate 60 to 80 horn fly adults if protected from insect predators and competitors such as dung beetles. As beetles feed, they compete with the fly larvae for food and physically damage the flies’ eggs. Fly populations have been shown to decrease significantly in areas with dung beetle activity. Dr. George Bornemissza found that 95% fewer horn flies emerged from cowpats inhabited by Onthophagus gazella, than from pats where beetles were excluded (Knutson, 2000).

Dung beetles are also reported to be effective biological control agents for gastrointestinal parasites of livestock. The eggs of most gastrointestinal parasites pass out in the feces of the host. The eggs then hatch into free-living larvae and develop to the infective stage. They then migrate onto grass, where they can be ingested by grazing animals, and complete their life cycle within the animal. If the manure/egg incubator is removed by beetles, the eggs perish and the life cycle of the parasite is broken.

On a pasture-management level, dung pat removal is beneficial for forage availability. Most ruminants will not graze close to their own species’ manure pats. Research has shown that the forage is palatable, but avoided because of the dung pile. Consequently, cattle manure deposits can reduce available acreage by as much as 5% to 10%. By completely and quickly removing the manure, beetles can significantly enhance grazing efficiency.

The tunneling behavior of beetles increases the soil’s capacity to absorb and hold water, and their dung-handling activities enhance soil nutrient cycling. An adequate population and mix of species can remove a complete dung pile from the surface within 24 hours. As the adult beetles use the liquid component for nourishment and the roughage for the brood balls, the dung pat quickly disappears. If manure is left on the surface, up to 80% of manure nitrogen is lost through volatilization; by quickly incorporating manure into the soil, beetles make more of this nitrogen available for plant use and limits volatilization to 5% to 15%.

The larvae use only 40% to 50% of the brood ball before pupating, leaving behind the remainder of this nutrient-rich organic matter for soil microbes, fungi, and bacteria to use in creating humus (Richardson and Richardson, 1999).

Ready to learn more? Check out ATTRA’s newly updated publication Dung Beetle Benefits in the Pasture Ecosystem. It discusses the important and interesting role of the dung beetle, including the benefits it provides in the pasture ecosystem. It contains information on dung beetle farming and relates an author’s experiences observing dung beetles.

References:

Knutson, Allen. 2000. Dung beetles: Biological control agents of horn flies. Texas Biological Control News. Winter. Texas Agricultural Extension Service. The Texas A&M University System.

Richardson, Patricia Q. and R.H. (Dick) Richardson. 2000. Dung beetles improve the soil community (Texas/Oklahoma). Ecological Restoration. Summer. Vol. 18, No. 2. p. 116-117.