Published: 30 Apr 2020
There are a many benefits from having dung beetles on farms which is why there is an an effort underway to introduce a new species in Tasmania.
Dung beetles are a common sight on many dairy farms. While there are native dung beetles in Tasmania, they are adapted to dealing with the dung of native animals. The dung beetles you see at work with cow dung are all introduced species and may include:
- Bubus bison
- Euoniticellus fulvus
- Geotrupes spiniger (also called “blue bomber”)
- Onthophagus taurus
- Onthophagus binodis
Over the last 12 months, the team at Cradle Coast Natural Resource Management (CCNRM) have been working with dung beetle experts to introduce another species in north-west Tasmania. Onthophagus vacca is a spring active dung beetle – a current gap in dung beetle activity in Tasmania. Introducing a new species of dung beetles is not easy – this is the third attempt at introducing Onthophagus vacca to the state. Why do we keep trying?
What do dung beetles do?
All the dung beetles in Tasmania are ‘tunnellers’. They burrow into the soil under dung pads and bury the dung in underground tunnels.
Adult dung beetles drink the juice from moist dung. This juice contains microorganisms (bacteria, yeasts, fungi and protozoa) from the digestive system of animals. These microorganisms provide the nutrition the adult beetles need. Removing the moisture from the dung leaves behind a fibrous mass. The dung beetle larvae feed on the buried fibrous dung which consists of partially digested plant material. The larvae further digest this fibre with microbes in their gut.
How do they help dairy farmers?
There are a number of benefits dung beetles provide to dairy farmers.
Reduce pasture fouling. One of the most visual benefits is dung beetles move most of the dung from the pasture to the soil. This can reduce the amount of unpalatable grass present in a paddock at the next grazing.
Increased yield. Studies in laboratories and field trials have shown increased plant growth when dung beetles are present. One study found increased growth in Japanese millet due to the presence of dung beetles was equivalent to the application of 150 kg of nitrogen and phosphorus per hectare. Another study recorded seasonal grass production at 7.8 t DM/ha with dung beetle activity compared to 6.4 t DM/ha with no dung beetles. Field studies conducted in Australia compared dung + beetle treatments to dung only treatment and found the dung + beetle treatment statistically showed higher growth. Interestingly, this improvement in growth continued for multiple years when compared to the dung only treatment, which did have improved growth when compared to the control but only for a number of months. Increased plant yields can be attributed to the increased cycling of nutrients from the dung and associated soil structure changes caused by dung beetle tunnelling.
Increased soil permeability. Dung beetle tunnels allow water to quickly penetrate the soil, reducing run-off during heavy rainfall events. This effect reduces over time – 12 months after dung beetle activity, the soil has returned to pre-dung beetle state but if there are always active dung beetle populations present, this can be a permanent improvement.
Reduction in the number of flies. One of the main reasons the CSIRO introduced exotic dung beetles to Australia was to reduce the number of bush flies. The larvae of bush flies, like adult dung beetles, feed on the manure juice. Once dung beetles remove all moisture from the dung, the fly larvae die as their food source dries up. Apparently, this has resulted in much lower numbers of bush flies around Australia (logically, this makes sense but based on personal experience sometimes it is hard to imagine higher numbers of bush flies than what we currently have!).
Reduction in animal parasites. Studies have shown dung beetles burying manure reduce the numbers of dung-borne parasites such as round worms, flatworms and protozoa (e.g. Crytosporidium). However, whether this has the flow-on effect of lower parasite levels in our livestock is not known and will be affected by factors such as stock management, the parasites life-cycle and prevailing seasonal conditions.
Threats to dung beetle survival
Dung beetles do have natural predators, which include birds and bats, although, populations are usually able to survive fairly high levels of predation. Of greater threat is the use of some particular drenches and insecticides. Most of the ‘mectin’ family of drenches are toxic to dung beetles, although careful timing for de-worming stock can make these drenches more dung beetle friendly. Good timing is based on understanding the life cycle of the dung beetle and by applying drench when dung beetles are consuming the least amount of the manure juice. As you would expect, many insecticides are toxic to dung beetles (an insect). If paddocks are sprayed with insecticide keep cattle out of areas sprayed for at least 7+ days (always observe the stock withhold period for any chemical).
There are many benefits gained from having dung beetles on-farm and most of the time we don’t need to do anything different to maintain a healthy population.
If you are really enthusiastic about dung beetles, you can download the MyDungBeetle App on iOS and android devices. More information is about the app and dung beetles is available from www.dungbeetles.com.au.
Find out more about the latest release of dung beetles in Tasmania by contacting Tom O’Malley at Cradle Coast NRM on 6433 8400.
Information for this article was sourced from these two books which make great further reading on the topic:
- Dung Down Under – dung beetles for Australia by Bernard Doube and Tim Marshall
- Ruminations of Poo-ologist – dung beetles in Tasmania by Graeme Stevenson