Dung under: Aussie example shows importance of beetles

A Dor Beetle

We in the West are meat-eating, milk-drinking people, but were farmers or ranchers obliged to compensate for the carbon emissions of their herds, they would be bankrupted. 

No emission preventative has yet been found, although a Dutch company claim that preliminary tests of a cattle-feed additive reduces the front-and-rear exhalations of these useful ungulates by over 60% in cows and 35% in steers.

Any solution would significantly add to Earth’s chances of surviving climate change. There are 1.5bn head of cattle world wide, 30m in Australia alone.

Some years ago, Jarvis Good, an entomologist at University College Cork, told me that grassland areas of Australia would be knee-deep in cow pats but for the introduction of a cow-pat eating beetle. These beetles do more than act as disposal units: In their workings, they renew and revive the land. Therefore, their decreasing numbers worldwide has led to serious concern.

Their useful role is illustrated in the history of Australian cattle-ranching. The first half-dozen cattle arrived in 1788, Indian Zebus, bought in South Africa by the First Fleet settlers. They were to be looked after by convicts, who — either fecklessly, drunkenly, or vengefully —let them escape into the wild. Thought to have been speared by aboriginals or eaten by wild dogs, a decade later, a 60-strong herd was discovered, looking after themselves.

Various bovine strains thrived on the continent and, by 1860, 1m cattle grazed Australia’s grasslands. Today, there are 30m but, in the years between, a serious problem arose. On the vast continent, there was no insect present to digest cattle dung. The leavings of kangaroos and wallabies, yes —beetles had evolved that dealt with these, but not with the cattle excreta, of which over half a million tons were deposited daily.

I realise that readers of delicate sensibility may, by now, have read enough on this theme, but I’m sure they will be gratified to know that, without the lowly dung beetles of the world, our planet would not only be literally but, also, ecologically in the mire.

In Europe, we did not have this Australian problem. In Ireland, cow pat beetles came in various sizes: Small ones flew about on summer nights and arrived indoors attracted by lights. Girls shrieked, I recall, more to amuse one another and annoy or attract boys, than from actual beetle mania (or Entomophobia). Boys rushed to come to the rescue of a friend’s pretty sister.

Meanwhile, far below them in Aussie, 30m cattle were dropping 300m cow pats a day, and not a beetle available to dispose of them. Each pat bred 3,000 flies, threatening the health of the herds and making rural Australian life almost unbearable in summer. Additionally, the unbiodegraded dung suffocated new growth and took 1m hectares of grazing land out of production annually. Also, cattle would not graze in the vicinty of their own leavings and grazed areas remained unproductive for two years.

The story of the what happened next is legendary in the annals of sustainable agriculture. The dung carpeting the fields was noticed by a Hungarian entomologist, George Bornemissza, recently arrived in Australia. He initiated studies which, in the late 1950s, led to a global search to find coprophagous (dung-digesting) beetles to clean up Australia. Specific species were required to suit the various diverse habitats and climates. Between the 1960s and 1980s, 55 were imported and released. Many became established and proved much more valuable than simple disposal units.

The modus operandi of dung beetles is to excavate tunnels beneath cow pats, lay eggs, and drag dung down to sustain the larvae. For every litre of dung buried, a litre of subsoil is brought to the surface. Meanwhile, less dung on the surface reduces the population of noxious flies.

After the larvae leave, the holes allow rain to penetrate the soil. When the pat is exhausted and the beetles move on, earthworms colonise the tunnels, transforming the remaining manure into granular, nutrient-rich earth worm casts, obviating the need for fertiliser. The mature beetles feed the food chain. Here in coastal West Cork, I see choughs, rare elsewhere, exploit the beetle food source.

Unfortunately, the widespread use of a new drug, Ivermectin, for ‘worming’ cattle gives reason for concern. In An Teagasc laboratory trials, it has been found to remain active in the dung of treated cattle. It kills 80% of dung beetle larvae, while the larvae mortality rate in the dung of untreated animals is only 15%.

We must carefully evaluate which human interventions deliver the best security for the land and our survival.


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