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Cow farts and burps are a big, smelly problem. They contain a lot of methane – a greenhouse gas that contributes to climate change. Kangaroos, on the other hand, produce a lot less methane when they toot.

Some researchers have suggested that kangaroos have a unique microbiome – a mix of bacteria in the gut that helps to digest food.

“But we have come up with another hypothesis,” says Dr Adam Munn from the University of New South Wales. “We think [kangaroos] produce less methane because of the way the food moves through the gut.”

The research group’s theory is based on experimental findings that, for the first time, link kangaroo methane production with food intake. “We found that if you reduce food intake by 75 per cent, the methane output goes up,” Adam explains.

A gassy experiment

The research was done with the help of Adam’s colleague, Dr Marcus Claus from the University of Zurich, and conducted by Swiss student Catharina Vendl at the University of New South Wales’ Arid Zone Research Station.

For 24 hours each, Catharina placed individual kangaroos into a large, sealed, see-through box and fed them one of two diets: an all-you-can-eat diet, or a restricted diet.

To work out how much gas the kangaroos produced, fresh air was pumped into the box, while the used air was sucked out and analysed. Catharina also collected the kangaroo’s poo to determine how much food had been digested.

The University of Queensland’s Dr Athol Klieve, who works in agricultural microbiology, isn’t convinced by the food intake hypothesis.

“There is a lot of speculation in terms of the microbiology of these animals,” he says. He also questions the experiment’s lack of a positive control. “Without ruminants [such as cows] in the exact same environment, it’s hard to compare.”

Adam is next looking at methane production in other animals, such as feral goats and dorper sheep. He is also keen to team up with microbiologists to better understand kangaroo microbiology.