Project Hopes To Explain Why Marsupials Are Better For The Planet Than Other Herbivores

The guts of kangaroos contain microorganisms that make for a much more habitable planet than ruminant counterparts fed on the same feed. Image credit: Andrea Izzotti/Shutterstock.com

The vast quantities of methane that cattle and sheep burp (and occasionally fart) represents one of the greatest threats to climate stability. Despite living on a similar diet, kangaroos and many other marsupials produce drastically less of this heat-trapping gas, but scientists have very little idea why. The University of Queensland has launched a new program to get to the bottom of this issue, although they currently have more questions than answers.

One certainty is none of the animals involved produce the methane themselves. Instead, micro-organisms in their (and our) guts break down food and produce methane in the process. Contrary to popular belief, methane production in the gut is not from bacteria, but a separate domain of single-celled organisms known as archaea. Kangaroos' guts are also occupied by archaea, yet for some reason, these produce drastically less methane when they turn grass into nutrients the host can absorb.

Professor Mark Morrison and Dr Paul Evans are part of a team seeking to identify what makes some archaea produce so much more methane than others. "A better understanding of this relationship could potentially help scientists find ways to reduce methane emissions in livestock, decrease greenhouse gas emissions from the agricultural sector and positively impact climate change,” Morrison said in a statement

Humans have our own archaea, but our diet is so different from cows' it's not particularly surprising that most of us are much lighter on gas production. Dr Evans told IFLScience the topic of marsupial archaea is so understudied that we don't even know how much less methane a kangaroo produces from the same amount of food as a cow. “It's somewhere between a tenth as much, and an undetectable amount,” Evans said.

The way it shapes their droppings into cubes isn't the only unusual thing about the wombat gut – its archaea (bottom) look quite different from those of humans (top). Image credits: James Volmer and Ana Laura Astorga Alsina from the Morrison group (bottom) James Volner (top).

If anything, the reverse might be expected. Australian grasses are generally of lower quality than those on other continents thanks to the drier climate and poorer soils, yet marsupial archaea haven't resorted to high methane production to process this rough material.

Curiously, although gut archaea differ among herbivorous marsupial species, the methane producers that they do have appear to be more similar, irrespective of diet. Again, Evans said much is unexplored, but “Wombats and sugar gliders have somewhat similar methanogens” to kangaroos, despite preferring roots and nectar respectively to grass.

No one, as far as Evans knows, has tried giving cows a kangaroo-poo enema (or vice versa) to see how each animal would do with the other's microbes on board. The results would likely be disastrous, but a more gradual adaptation of marsupial archaea to the bovine gut might be worth exploring.

Some have suggested farming kangaroos for meat as an alternative, an idea that creates a rare alliance of beef farmers and animal rights activists against it. Evans didn't want to be drawn on the merits of the idea, other than telling IFLScience; “I think it would be very difficult, they're wild animals, hard to domesticate.”

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