On 8 October 2013, Landcare Research’s invertebrate ecologist Dr Shaun Forgie announced the release of two new species of dung beetles, Onthophagus taurus and Onthophagus binodus, on New Zealand farms following years of research and consultation.
The article, Dung beetle mania, looks at the early days of this project.
Effects of large amounts of dung
Intensive farming sees large amounts of dung dropped onto pastures, and while it can break down naturally, the sheer volume means that often excess nutrients are leached into waterways and pastures become fouled, spreading parasitic worms and reducing the amount of grass available for farm animals to eat.
However, a tiny army is at hand. Dung beetles bury the dung of large grazing animals, such as sheep and cattle, which improves soil health and pasture productivity, reduces water and nutrient run-off and helps to prevent the reinfection of livestock by parasitic bugs.
Native dung beetles
Dr Forgie writes that New Zealand has its own forest-dwelling native dung beetles, but unfortunately these do not live in pasture. We also have another introduced dung beetle from Mexico, but this only lives in the warmer climate at the top of the North Island.
The two new species were released on an organic farm in Gore and on another property in the Wairarapa.
Mass-reared dung beetles
“Permission to import and release 11 additional species of dung beetles was received from the Environmental Risk Management Authority (now EPA) in February 2011, and the beetles were initially held in containment at Landcare Research until given disease clearance by the Ministry for Primary Industries. Once released from containment in 2012, dung beetles were mass reared at both Landcare Research’s campuses in Lincoln and Tāmaki. Some caged field trials were also undertaken to test how the beetles might perform,” writes Dr Forgie.
What happens when dung is buried by beetles
Dung beetles use grazing animals’ poo for food and reproduction. The two recently released species make tunnels in the soil beneath the dung, which they then bury to lay eggs in.
As the eggs hatch, the grubs eat the dung, breaking it down and turning it into a sawdust-like material that adds to the fertility of the soil structure.
“As the eggs hatch, the grubs feed on the dung to grow and develop into new adults. Remaining dung is utilised by earthworms and microorganisms in the soil that make the nutrients available for uptake by grass roots. Buried dung has been shown to increase earthworm numbers, increase soil fertility, improve soil structure and increase the depth at which grass roots grow. Consequently, grass becomes more drought tolerant. At the same time, dung beetles get rid of dung sitting on top of the pasture, reducing forage foul and forage avoidance around repugnant dung,” writes Dr Forgie.
Large amounts of dung can cause excess nutrients to be leached into waterways. Your students can learn more about this by trying this activity, which demonstrates how substances are dissolved and transported by water through the soil.
Water and nutrient leaching
For more information on dung beetles in New Zealand, see this website.