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Dung Beetles: Fundamental Soil Specialists

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Background

Dung-Beetle

Figure 1: A small dung beetle at JIngeri. This is either a native beetle or one of the smaller introduced species.

Because we are so passionate about our soils at Jingeri, it goes without saying that we are equally as passionate about Dung Beetles. One of the most ancient lineages of all insects, these delightful animals trace their ancestry back to the days when Australia was a part of the large land mass known as Gondwana, which also included, Africa, Antarctica, South America and Madagascar as part of this prehistoric land[i]. These beetles first evolved in what is now southern Africa and dispersed outwardlyi. Today they are found on every continent on Earth other than Antarctica, with the second oldest lineages of dung beetles found in Australia and South Americai. One quarter of all animals on earth come from the beetle family (Coleoptera) and of these, more than 250 genera and 6000 species are dung beetles[ii].

This huge diversity is responsible for the ongoing success of these animals and testament to their unique, genetic, physical and behavioural traits. Because of these traits they have been able to exploit ecosystem niches in a variety of climatic and terrestrial environments, with the greatest diversity of these beetles (as is the case for most biodiversity) occurring within tropical forested zones. From a scientific perspective, these reasons are why they are considered an important indicator species for assessing ecosystem health and levels of biodiversity. Dung Beetles can be broadly categorised into four main behavioural groupings:

Dung-Beetle-2

Figure 2: A partly processed dung pad with an obvious dung beetle tunnel at Jingeri. In order to ascertain what kind of tunnel this leads to, the soil beneath the dung pad would need to be excavated.

  1. Endocoprids – single tunnel directly beneath the fresh dung pile
  2. Paracoprids – Make complex nests away from the dung pile by tunnelling underground
  3. Telocoprids – Make dung balls that are rolled away to a remote nesting site
  4. Kleptocoprids – Dung ball thieves! These steal freshly rolled dung balls from other beetles in which to lay their eggs

The Australian Case

Whilst Australia hosts the second oldest lineage of Dung Beetles worldwide, the species diversity is much smaller than for most other nations. In total we have 443 species in 30 genera in Australia[iv]. This is arguably due to wide climatic variability and our lack of large endemic grazing mammals, though in earlier geological times when Australian mega fauna existed, dung beetle diversity may well have been much greater than today. One of the issues limiting our knowledge of dung beetles globally is a lack of fossil evidencei.

Another issue for Australian dung beetles is that they are not effective dung recyclers of large dung pads like those from cattle. On the other hand Australia is host to one of the few species of dung beetle that target fungi as a food source, as well as several species that hitchhike (phoretic) on the fur of the dung host animal – the ultimate in meals on wheels![v]

Native versus Introduced species

Dun-Beetle-Distribution

Figure 3: Distribution of introduced dung beetle species throughout Australia 2007. Source: Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch12, pp.256)

Because of the limited ability of Australian species to deal with the over-abundant supply of dung from introduced grazing animals, particularly cattle, a variety of overseas species have been introduced to Australia to combat this issue. A form of biological control, this can and does come with unintended side effects. The cane toad in Australia is the penultimate example of massive failure in this regard and is now a threat to some of Australia’s most fragile ecosystems, not to mention pet dogs and cats. Because of this a great deal of scientific study has been conducted to assess the effects of introduced dung beetles on native populations. This is especially critical in QLD which is home to 355 of the 443 native species. QLD is also one of the largest sheep and cattle grazing states in the country, with millions of sheep and cattle dropping dung on farms across the state.[vi]

Native species fall mostly within one genus, Onthaphagus, which includes the few native species that can be found targeting cattle dung. Species diversity of native beetles within Qld is highest in rainfall zones between 500-1200mm per annum[vii]. The other species of native beetles occur mostly in forested areas within the sub-tropical rainfall zones and studies have shown that native beetle abundance is lowest in areas with rainfall above 1600mm per year[viii]. The good news is that since the gradual introduction of 43 dung beetles species since the 1960’s, native dung beetle abundance has generally increased in tandem with increases in introduced species over time. In 2007 it was found that 23 species of the original 43 introduced had become well established over broad geographical areas. Today the highest introduced species diversity occurs in SE QLD. Study has found that native populations of only one native species (Onthaphagus ferox)[ix], declined due to competition from introduced species.

Dung Beetles: The critical ingredient for healthy pastures in stock grazing systems

Dung-Beetle-4

Figure 4: A dung pad that is almost completely broken down, the result is a fluffy appearance of loosely mixed dung and soil remaining on the soil surface. In another day this dung pad will be completely recycled deep into the soil.

As most farmers are aware, it is incredibly detrimental to pasture growth and hence your bottom line, to have paddocks that consist of hundreds of aging dung pads sitting on the ground and drying out. Once a dung pad dries out, dung beetles and other insects tend not to target them as a food or nesting source. If there are insufficient dung beetles to recycle the dung deep down into the soil profile quickly before it becomes dry, then that dung will sour pasture grasses, slow or prevent new growth and become a point source for pests such as fly species. Biting flies in particular are a major problem for cattle farmers, whilst blow flies cause fly strike in non-mulesed sheep. Both these issues present major production costs both in prevention and treatment of affected animals. From a human health perspective, the more dung laying around, the more flies we have to annoy us at our Sunday BBQ’s! It is well known within farming circles that biting flies and fly strike are one of the biggest animal husbandry issues on farm, so often farmers resort to chemical control methods. However if these issues can be avoided through prevention of the problem in the first place, it is always going to be a healthier and cheaper option. Also many chemicals used in farming, kill dung beetles and other soil animals, meaning that some farms are essentially devoid of healthy soil ecosystems because of persistent chemical use historically. This can lead to issues such as poor pasture/crop growth, increased risks of erosion, and an increasing need for expensive chemical inputs to account for the nutrient imbalances that come from a lack of dung recycled into soils.

Dung-Beetle-5

Figure 5: Multiple fungi species growing out of a two day old dung pad after rain at Jingeri. This paddock is known to have healthy numbers of dung beetles also.

Aside from all of the above, as for all ecosystems, when a fundamental part of the food web within that ecosystem is removed (i.e. the dung beetles) then other parts of that ecosystem collapse as a result of the loss of complex interrelationships. Where dung beetles and soil bacteria and or fungi are closely linked, if one is affected then all will be affected as a result and pasture productivity declines will follow. If we are to find smarter ways to farm in to the future, then promoting the work of dung beetles should be high in all our agendas. By incorporating these lovely creatures into our farming regimes, then we as farmers will reap multiple benefits, not least of which is a reduction in input costs. Assessing whether you have dung beetles is not difficult, and a link to instructions courtesy of “Dung Busters” on how to set up a dung beetle trap can be found here. In QLD you can have your specimens identified by taking them to the museum. Some Universities may offer services in this regards also.

REFERENCES

[i] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles.
[ii] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch1, pp. 1; ch11, pp. 221).
[iii] Sabi Sabi (2012) http://www.sabisabi.com/wildfacts/dung-beetles
[iv] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch2, pp.22).
[v] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch2, pp.40).
[vi] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch12, pp.252)
[vii] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch12, pp.252)
[viii] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch12, pp.252)
[ix] Simmons & Ridsdill-Smith ed. (2011), Ecology and evolution of dung beetles (ch12, pp.263)
Tracy Finnegan
Tracy Finnegan

My name is Tracy Finnegan. I have recently graduated form the University of QLD with an extended major: BAppSci – Integrated Resource Management. Formerly I was an Intensive Care/Emergency Department Registered Nurse and have been involved in running our family business for the last 12 years.

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Showing 2 comments

  • Basement Windows
    Reply

    Great blog you have here but I was curious about if you knew
    of any discussion boards that cover the same topics talked
    about here? I’d really love to be a part of group
    where I can get suggestions from other experienced individuals that share
    the same interest. If you have any suggestions, please let me know.
    Thank you!

    • Tracy Finnegan
      Reply

      Hi!
      Thanks so much for the question and the quick answer is that I don’t know of any specific discussion pages for dung beetles, however there are a number of great websites that you can visit, some of these have links on our resources page. There are also a number of Facebook groups that you can follow or become part of that are concerned with holistic soil management, for example ‘SARE’ Sustainable Agriculture Research and Education, or the Global Soil Biodiversity Initiative.
      It’s so great to know that there are people out there who are concerned about the small things in nature!!
      Cheers
      Tracy

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