FROM THE FRONT LINE All about poop and na­ture’s re­cy­clers


Dung bee­tles were in­tro­duced from Europe to save us from be­ing buried in ma­nure. Now re­searchers be­lieve they might also help us mit­i­gate green­house gas emis­sions. BELINDA SMITH re­ports. When Euro­pean set­tlers brought cat­tle and sheep to Aus­tralia, they didn’t just bring food sources – they brought ver­i­ta­ble poop fac­to­ries. The so­lu­tion to the prob­lem came in the form of for­eign dung bee­tles. The Univer­sity of New Eng­land’s Min Raj Pokhrel aims to find out how the lit­tle crit­ters are far­ing – what tem­per­a­tures they pre­fer and how they might mit­i­gate green­house gas emis­sions – in the New South Wales North­ern Table­lands.

A sin­gle cow poops about 10 times a day; with about 30 mil­lion cat­tle in Aus­tralia, that’s 300 mil­lion cow pats plop­ping daily onto the ground. In Europe, cow dung is pol­ished off by dung bee­tles. Adult bee­tles bury it, eat it and lay eggs in it, so their lar­vae can also feed on it once hatched. Dig­ging dung into the ground also has the ben­e­fits of dis­pers­ing grass seeds, not to men­tion fer­til­is­ing and aer­at­ing the soil, let­ting wa­ter more eas­ily soak into the earth and giv­ing plant roots room to grow.

Even though the na­tion boasts more than 400 species of dung bee­tle, none were up to the task of deal­ing with cow poo. Na­tive dung bee­tles evolved with mar­su­pi­als such as wal­la­bies and kan­ga­roos. Adapted to hard, small, fi­brous poops, they couldn’t deal the big wet splats from cows.

With­out in­tro­duced dung bee­tles, splat­tered dung would foul pad­docks, shrink­ing graz­ing land and pro­vid­ing per­fect breed­ing spots for dis­ease- Cat­tle pro­duce 300 mil­lion cow pats a day. CREDIT: IPG GUTENBERGUK LTD / GETTY IMAGES spread­ing flies and par­a­sites. Pats, once they har­den on the ground, can sit there for months – even years.

Hun­gar­ian en­to­mol­o­gist Ge­orge Borne­mis­sza no­ticed this in the 1950s when he first set foot in Western Aus­tralia. Less than 200 years af­ter cat­tle had been in­tro­duced to Aus­tralia, cow poop was a prob­lem of epic pro­por­tions. Bush fly pop­u­la­tions were be­com­ing un­bear­able, and farm­ers were forced to con­tend with ris­ing worm and bac­te­rial in­fec­tions in cat­tle stock.

In Europe, poop just wasn’t such a big deal. Borne­mis­sza won­dered if Aus­tralia could en­list some out­side help. Would in­tro­duced dung bee­tles clean up af­ter cat­tle?

He had to tread care­fully. In­tro­duced species have a habit of run­ning out of con­trol in Aus­tralia. Af­ter a decade of re­search­ing dung bee­tles from around the


world, the first large-scale re­lease took place in 1967. Four species – a to­tal of 275,000 bee­tles – were let loose, mostly in north­ern Aus­tralia be­tween Broome in Western Aus­tralia and Townsville in Queens­land.

Since that first clus­ter al­most 60 dif­fer­ent dung bee­tle species have been in­tro­duced from Africa, Europe and Asia, the most re­cent be­ing On­thoph­a­gus vacca, in 2014, and Bubas bubalus, in 2015.

So how are the in­tro­duced bee­tles far­ing – and what about their na­tive coun­ter­parts? These are ques­tions Pokhrel aims to an­swer dur­ing his PHD re­search.

He is tak­ing stock of their pop­u­la­tions, count­ing them in 10 lo­ca­tions across el­e­va­tions from 300 me­tres to 1,300 me­tres above sea level in the North­ern Table­lands. Even at the high­est alti­tudes, Pokhrel ex­claims, “We still found them!”

He is also mon­i­tor­ing when are they most ac­tive – do they pre­fer the sum­mer heat or the chill of win­ter? – and how far in­tro­duced bee­tles, which are quite good fly­ers, have spread.

He’s also get­ting his hands dirty. Part of his project is de­ter­min­ing what type of poop na­tive dung bee­tles like. Has their ap­petite changed with the avail­abil­ity of sheep and cow dung? So far, he’s found some na­tive dung bee­tles have de­vel­oped a taste for sheep poop. This may be be­cause sheep dung is more nu­tri­tious com­pared to that from kan­ga­roos, he says, or per­haps the na­tive dung bee­tles have adapted to wet­ter, less fi­brous poops. There’s still more work to do be­fore draw­ing a con­clu­sion.

Pokhrel is also keen to un­cover what it is about dif­fer­ent species’ poop that at­tracts dung bee­tles. He thought wa­ter con­tent might play a role, so to test this he mixed sheep and kan­ga­roo drop­pings with wa­ter to make them the same con­sis­tency as cow pats.

“They looked the same for me, but it was very dif­fer­ent for dung bee­tles,” Pokhrel says. Dung bee­tles that pre­ferred sheep drop­pings con­tin­ued to favour them, even in their sludgy state. Like­wise, cat­tle-spe­cific bee­tles stuck to their usual, even with wa­tery sheep and kan­ga­roo poop on the menu. So how do green­house gases fit into the equa­tion? Cows burp and fart meth­ane – a green­house gas 28 times more po­tent than car­bon diox­ide – but their dung can pump it out too.

Grass­lands and pas­tures are usu­ally car­bon sinks, with plants tak­ing up car­bon diox­ide for pho­to­syn­the­sis. But cover even a frac­tion of a pad­dock with cow pats and it be­comes an emit­ter. On top of this, meth­ane-pro­duc­ing mi­crobes pre­fer an oxy­gen-free en­vi­ron­ment – pre­cisely what a sloppy, dense cow pat pro­vides. If the pat is bro­ken apart and aer­ated, per­haps by a dung bee­tle look­ing for a place to lay its eggs, then car­bon diox­ide-pro­duc­ing bac­te­ria take over.

Euro­pean and US stud­ies have shown this to be the case. Six-day-old dung pats with­out dung bee­tles pro­duced meth­ane emis­sions five times higher than those with the bee­tles. Pokhrel will see if this ap­plies in the Aus­tralian con­text – and might find yet an­other rea­son to cel­e­brate na­ture’s re­cy­clers.

Dung bee­tle (Scarabaeus sacer) hard at work.


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