Einstein Science Reporting for Kids
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Contact: Tomas Roslin
University of Helsinki

Kids join scientists in finding out who gets rid of cow poo

A volunteer in action. Mari Hamppula has installed cages to exclude given decomposer animals from dung pats behind her on the right. She now samples pats used as bait to establish what dung beetle species are present on her home farm. (Photo: Timo Marttila/Satakunnan Kansa)

Have you ever thought about how much poo is produced in the world? Just each cow produces about twelve pats a head every day. And with more than a billion cows around the world, we are talking about an immense amount of yes, exactly that.

Clearly, someone is cleaning up all this waste, as the world is still green rather than brown. Now a team of scientists have joined forces with local kids to find out who eats most of it in a country called Finland, in Northern Europe.

Dor beetles are the best

The largest part of a cow pat is broken down by microscopic germs, or just takes off as the pat dries out. About one-eighth (13%) is removed by small animals, mostly insects and other invertebrates.

Not all of these animals are equal: Of all the bugs making a living off the dung, large tunnelling Dor beetles removed dung twice as fast as smaller dung-dwelling beetles and earthworms.

Importantly, climate has just as strong an effect on dung disappearance as do dung-eating animals: the pats in Southern Finland decompose much faster.

Large tunnelling dor beetles in the genus Geotrupes. Dor beetles (genus Geotrupes) proved the most efficient decomposers. They remove dung twice as fast as do smaller dung-dwelling beetles and earthworms. (Photo: Riikka Kaartinen)

Kids as citizen scientists

Comparing the impact of animals and climate was only possible because the scientists did the same experiment at about 80 sites across a whole country. To do this, they used something called citizen science.

"Citizen science is about having people who are not scientists joining in to do science. If everyone looks in their own back yard, we can then together form the big picture" explains Riikka Kaartinen, who kept the whole project together.

"In our case, we asked teens to take fresh cow pats from the barn, shield some of them from certain bugs with cages that we sent them, and then look at changes in pat weight."

Strength in numbers

"Our strength comes from our numbers", says Bess Hardwick, who taught the kids how to do the experiment, and answered their questions throughout the summer. "A lot of changes in nature will only be noticed if followed by a large number of eyes like if some animals change their ranges southwards or northwards, or if they get rarer."

"What we did was to take citizen science one step further, by moving from 'just' observing nature to changing something, excluding certain groups of animals" says Tomas Roslin, the leader of the research group. "Changing something and looking at what happens, that is the whole idea of experimental science."

"The important thing here is that we can do so much more if we just join forces", adds Tomas. "In citizen science, our own imagination is really the hardest limit to what we can do together."


For more information, contact Riikka Kaartinen (riikka.kaartinen@slu.se) or Tomas Roslin (tomas.roslin@helsinki.fi)