Reflections on dung
When we think of dung beetles (which admittedly is not that often), we tend to think of the two dozen or so species that were introduced by the CSIRO to aid the dispersal of cattle dung and thus reduce the problems of pasture fouling and fly breeding. But Australia has its own dung beetle fauna – apparently more than 500 species! Although some of these will tackle cattle dung, the denser, drier fibrous pellets of native marsupials are much more to their liking.
Walking past a patch of decomposing Common Wombat scats we noticed movement and, on inspection, active below the surface were several dung beetles. One of the beetles is shown in the photo above, and was identified by our dung beetle guru, Bertram Lobert, as most probably Onthophagus australis, a native species that can also be abundant in cattle dung at times. So we started to take a greater interest in the faeces of our local wombats, and discovered that the relatively rapid breakdown by dung beetles appears to be a rarity – most of the cube-shaped pellets seem to hang around for some time, hardening and fading before eventually crumbling.
As well as wombats, there are plenty of Eastern Grey Kangaroos on our property at present and, as far as we can tell, there are no dung beetles active in their numerous droppings – like the wombat scats, the pellets just dry over time and eventually crumble to dust, so that there is a range of shades from almost shiny black fresh scats to very pale older ones.
This got us thinking: have native dung beetle numbers declined? And if so, is it due to human agricultural activity – such as use of chemicals, soil compaction, mechanical disturbance, etc. Or have the beetles simply gone with the flow, so to speak, and switched to the more abundant and readily available cattle dung?
We have no answers and would welcome any comment. Results of internet searches are dominated by articles and information on introduced dung beetle species. However we did come across an article by Nicole Coggan titled Are Native Dung Beetle Species Following Mammals in the Critical Weight Range towards Extinction? which considers dung beetles in relation to small native mammals, but not kangaroos or wombats.
It would be a great pity if native dung beetles are declining, because one of the services they provide is to tunnel, sometimes quite deeply, into the soil to bury dung, thus not only enriching the soil, but also improving rain penetration. We’ll continue to keep a scatological eye on what we have available.
Focus On Fauna 