Dung beetle benefits - Improving soil health in pastures

Kick over a cowpat in a paddock anywhere in Australia, and you might find a home to a myriad of creatures. For the livestock industry, some are not what you want to see - like nematodes or fly larvae - but if you're lucky, or maybe proactive, you might find some tiny beetles working hard to improve your pastures.

Geotrupes spiniger in hand.

In the late 1950s, a scientist named George Bornemissza noticed a difference between Australia and his home country of Hungary. The pastures weren't coping with the influx of introduced livestock, leaving a layer of manure on the surface, smothering grass and causing runoff into waterways when it rained.

I can't tell you a negative outcome from the introduction of dung beetles.

Associate Professor at Charles Sturt University Dr Russ Barrow said the impact non-native livestock was having on the Australian environment was unsustainable. 'In Australia, you had horrible situations where paddocks were fouled. Imagine having 100 acres with 20-50 cattle in there, and the dung was just sitting on the surface,' Dr Russ Barrow said. '[The dung] was a fantastic breeding ground for flies and nematodes, and it just sat there.'

Following a hypothesis that European dung beetles had evolved alongside livestock to manage and process the dung, the CSIRO launched the Australian Dung Beetle Project in the early 1960s, introducing species to try and tackle the issue.

'Australia actually has around 500 species of native dung beetles, so we do have a huge diversity and abundance of native dung beetles,' Dr Barrow said. 'But they've evolved to operate and process the dung of kangaroos, wallabies and wombats. Not livestock.'

Australia actually has around 500 species of native dung beetles ... But they've evolved to operate and process the dung of kangaroos, wallabies and wombats. Not livestock.

The CSIRO searched for and identified a number of international species of dung beetle that favour open grazing environments - and preferentially feed on the dung of sheep and cattle - to introduce to Australian pastures. Now, some 60 years on, Australian livestock producers rely on between 20 and 30 of dung beetle species that have been introduced and established in the country. 'So they were carefully selected for those parameters, and we're 60 years on, and I can't tell you a negative outcome from the introduction of dung beetles,' Dr Barrow said.

Entomologists characterise three types of dung beetles in the world: dwellers, tunnellers and rollers. The focus in Australia was on introducing tunnellers. Despite the name, most dung beetles don't actually feed on solid dung; rather, they suck up the moisture, eating bacteria and fungi before digging a tunnel into the soil and taking dung for their larvae.

The tunnelling changes the bulk density of the soil; what was once compacted is now more porous.

By tunnelling up to a metre underground, the beetles aerate the soil, bringing buried nutrients to the surface and fertilising the deeper soil. The aeration of the soil also increases water absorption rates and reduces nutrient runoff during weather events. 'The tunnelling changes the bulk density of the soil; what was once compacted is now more porous,' Dr Barrow said.

An analysis of 24 studies across 14 countries was published in Proceedings of the Royal Society B: Biological Sciences in early 2024. The study found that the beetles can positively impact plant growth by up to 17%. The lead author was PhD candidate Daniel Anderson from the University of Western Australia. His team found that the improved plant growth was seen through thicker leaves rather than taller shoots, which allowed for greater photosynthetic capability. You can read the full scientific analysis here or this summary by the University of Western Australia here.

So what we find is that the dung beetles in good abundance can really suppress the fly population.

Beyond improving soil health, the tunnelling dung beetles also help improve livestock health by reducing the environment in which flies and nematodes grow. As the dung pats can be dehydrated and buried by the beetles within a day, the environment quickly becomes inhospitable to maggots. 'So what we find is that the dung beetles in good abundance can really suppress the fly population,' Dr Barrow said. By reducing the amount of manure on the surface, dung beetles are also able to disrupt the life cycle of gastrointestinal parasitic nematodes, which are re-ingested as third-stage larvae.

Even as Australian pastures have seen the benefits of dung beetles, Dr Barrow said there are still some climates and seasons that have yet to find a successful beetle to target specific issues. 'At the moment, it's due to bad luck, not bad planning, that the dung beetle species introduced to Australia haven't been effective in Queensland during late winter and early spring, just when buffalo flies start to breed,' he said. 'So we've got this gap in dung beetle activity in spring, so the buffalo flies can breed up and cause issues because there are no dung beetles.'

However, the hunt for the ideal new species is ongoing, including into parts of northern Africa, in hopes of finding a beetle or predatory insect that could help reduce buffalo flies for Queensland producers.

Dung beetle activity on a dung pat.

While native and introduced dung beetles can be found all around Australia, coverage, both regionally and seasonally, can be sporadic. Dr Barrow suggests first identifying what kind of dung beetles you already have on your property. This can then identify what seasons of the year they're active and what gaps you may have. Australian commercial suppliers can sell beetles suited to your climate and soil types; you can find a list of Australian suppliers here.

Knowing what seasons the beetles are already servicing and, therefore, what gaps you may need to fill can be useful for creating continuous beetle production. 'What we try to encourage producers to do is to be aware of the dung beetles that are operating on their property at certain times of the year,' Dr Barrow said.

As your diversity and abundance of dung beetles goes up, your reliance on drenches should go down.

He also advises producers to be mindful of the timing when drenching livestock for gastrointestinal nematodes. Ideally, higher chemical drenches should be applied during periods of low dung beetle activity. Producers can achieve this by testing manure in a lab to check for nematodes and drenching based on the results, rather than sticking to a fixed calendar schedule.

'Eventually, we'll get to the stage where we've got good dung beetle coverage throughout all the seasons, and then what we should observe is a reduced reliance on these animal health chemicals,' Dr Barrow said. 'As your diversity and abundance of dung beetles goes up, your reliance on drenches should go down.'

Dr Barrow says that despite the initial start-up costs of buying dung beetles, they quickly provide a return on investment, reducing the need for chemical inputs, improving livestock health overall and increasing pasture density.