Benefits of dung beetle introduction

Large grazing animals have been introduced to New Zealand without the agents that have evolved in their places of origin to process their dung.

The rapid removal and processing of dung by dung beetles can result in many benefits including:

Improved soil health and reduced runoff

Beetle tunnelling leads to increased aeration of the soil allowing water to penetrate better. Tunnelling and dung burial also result in increased grass root growth and biological activity in soils under and adjacent to dung pats. Dung beetle activity therefore leads to reduced run-off of rainfall and better retention of dung and urine in the soil. This in turn results in reduced microbial contamination in run-off, less leachate pollution and reduced eutrophication.

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Increased pasture productivity

Stock will not graze around dung pats, unless forced to by high stocking rates or having restricted access to pasture, which reduces pasture productivity. Dung burial by the beetles enhances grass growth through nutrient recycling, and increases the amount of pasture available, improving long-term sustainable productivity.

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Reduced infection of livestock by parasitic worms

Dung beetle activity reduces reinfection of livestock by parasitic worms. This is achieved by dung beetles directly or indirectly killing the eggs and young larvae of the parasitic worms. They do this in several ways. Firstly, the dung pat dries out faster as it is broken up by dung beetles – this kills parasite eggs and larvae faster than in dung pats without beetles. Secondly, the processing of dung into brood balls by the adult beetles, and direct feeding by dung beetles and their larvae, kill parasite eggs and larvae. Thirdly, deep burial of dung reduces vertical migration by parasite larvae back up to the soil surface.

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Reduced fly pests and human disease

Faster burial of dung will reduce the incidence of nuisance flies. Blowflies associated with sheep flystrike do not breed in animal waste but females use it as nutrient resource for maturing eggs. In New Zealand, other nuisance flies such as biting stable flies, house flies, and flesh flies are known to breed in livestock dung. When dung burying beetles and dung breeding flies compete in dung, the beetles win. Survivorship of fly eggs and larvae is significantly reduced by rapid conversion of the dung resource and mechanical damage during dung manipulation by the beetles. Many laboratory and field experiments confirm significant reductions in the numbers of dung breeding pest flies because of dung beetles.

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Reduced greenhouse gas emissions

The burial of animal waste and improved infiltration of urine into upper soils will likely reduce the production of methane and nitrous oxide, and is therefore likely to decrease the emission of greenhouse gases associated with animal waste. While adequate quantification of the influence of dung beetle activity on nitrogen emissions remains to be done, some studies have shown dung beetle activity during feeding and nesting will stimulate aerobic conditions, altering the microorganism fauna in dung pats, brood balls and associated soils to reduce methane production. And when compared to unburied dung, the speed at which freshly deposited dung is buried by moderate to high numbers of dung beetles is also likely to reduce methane production.

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Economic benefits

Economic benefits from dung beetle activity will arise from enhanced forage palatability, nutrient recycling and a reduction in pasture pests (e.g. nuisance flies and livestock parasites). New Zealand data are lacking, but conservative estimates from the United States suggest that by burying cattle dung alone, dung beetles are worth approximately US$380 million annually to the US economy. Dung beetles would also provide the same services for other livestock dung.

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