Think cows are stinky? Kangaroos have potent farts too, suggests a new study that found that the marsupials release significant amounts of methane into the air.
The discovery, reported in the Journal of Experimental Biology, negates a prior theory that kangaroos possessed "unique microbes" that heavily reduced methane production.
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"Kangaroos are not mysteriously low methane-producing creatures, but herbivores with an active methane-producing microbe community," co-author Marcus Clauss from the University of Zurich said in a press release.
He and his team are focused on the issue because methane is a known greenhouse gas that can contribute to climate change.
The researchers found that the amount of methane per kangaroo food intake could vary over just a few days.
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"If the animals eat less, i.e. the food remains in their foregut for longer and the bacteria have more time to digest, they produce more methane per food intake," said co-author Adam Munn from the University of Wollongong.
Scientists are considering many different options to solve the problem, from dietary changes to breeding animals whose food doesn't remain so long in their foreguts, to address the problem.
For the study, a group of Clauss' colleagues had the unenviable task of measuring everything that went into and came out of kangaroos to determine just how much methane the marsupials produced via their farts, and how efficient their digestion system was at curbing such gas.
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The researchers fed alfalfa to kangaroos housed at the New South Wales' Fowlers Gap Research Station. The alfalfa was given at two different levels: a restricted diet versus all the kangaroos could eat. The team then measured the animals' methane production and metabolic rates and also collected their feces.
Next, back at a lab in Switzerland, scientist Michael Kreuzer analyzed the nutrient content of the kangaroo's feed and poop to find out how much food the kangaroos had digested in relation to the amount of methane they produced.
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The researchers determined that a kangaroo produces about as much methane per year as a horse. Previously, it was discovered that a single adult horse can fart 45.5 pounds of methane gas annually. This is obviously an impressive amount, but still far less than that of cows.
"If the gas production (of kangaroos) is correlated with the amount of food ingested, however, the amount of methane is higher and therefore closer to the ruminants again," Clauss said. "In other words, the digestion process itself in kangaroos is not all that different to a cow's."
Photo: Kangaroos. Credit: A. Munn, University of Wollogong