Kangaroo Farts: The Low-Methane Marsupials
Kangaroos became scientific celebrities when researchers discovered that their digestion releases far less methane than that of cows and sheep. The story of why is a fascinating tale of gut microbes, climate science, and a few busted myths.
The Methane Mystery of the Outback
Like cattle and sheep, kangaroos are foregut fermenters: they rely on a large chamber full of microbes to break down tough, fibrous plants before digestion continues. In ruminants, this fermentation generates enormous volumes of methane, a potent greenhouse gas belched and passed by the billions of livestock worldwide. For decades, scientists noticed something curious about kangaroos — despite eating similar grassy diets, they seemed to release strikingly little methane. This observation turned the humble marsupial into an unlikely climate-research icon. If kangaroos could ferment plants efficiently without producing so much methane, understanding their digestive chemistry might hold clues for reducing emissions from agriculture. The mystery launched a wave of studies into exactly what lives inside a kangaroo's gut and how it differs from a cow's.
Foregut Fermenters Without the Methane
The secret lies in the microbial community of the kangaroo foregut. In cattle, archaea called methanogens consume the hydrogen produced during fermentation and convert it into methane. Kangaroos, by contrast, host a different balance of microbes dominated by bacteria such as Succinivibrio and other acetogens. Instead of funneling hydrogen toward methane, these microbes favor a process called reductive acetogenesis, which combines hydrogen and carbon dioxide to form acetate — a useful fatty acid the animal can absorb as energy. The result is a fermentation system that disposes of hydrogen without generating much methane, while extracting more nutrition from the same mouthful of grass. This elegant microbial alternative helps explain why kangaroos can thrive on poor Australian vegetation while keeping their methane footprint comparatively modest.
What the Research Actually Revealed
Early enthusiasm suggested kangaroos might produce almost no methane at all, but careful measurement told a more nuanced story. A widely cited 2015 study, with kangaroos placed in respiration chambers, measured their gas output directly. The animals did produce methane — just far less per unit of food than cattle or sheep. Their emissions were roughly comparable to those of non-ruminant herbivores like horses, and methane yield actually dropped relative to intake as the animals ate more. In other words, kangaroos are not magical zero-methane machines, but they are genuinely low emitters. The findings tempered some of the early hype while confirming the core insight: marsupial digestion really does keep a lid on methane in a way that ruminant guts simply do not.
Can Kangaroo Gut Microbes Fight Climate Change?
The tantalizing question is whether kangaroo gut bacteria could be transplanted into livestock to slash agricultural methane, which accounts for a large share of human-caused emissions. Researchers, including teams in Australia, isolated acetogenic bacteria from kangaroos and wallabies in the hope of seeding them into cattle rumens. In practice this has proven difficult: the cow's existing microbial ecosystem tends to outcompete the newcomers, and methanogens quickly reestablish themselves. Still, the kangaroo's biochemistry continues to inspire alternative strategies, from feed additives like seaweed and 3-NOP that inhibit methanogens, to selective breeding of low-emitting animals. While we may never simply give cows a 'kangaroo gut', studying these marsupials has deepened scientists' understanding of how to redirect hydrogen away from methane — a key lever in the effort to make food production more climate-friendly.
Did You Know?
- Kangaroos are foregut fermenters, much like cows — but their gut chemistry handles hydrogen very differently.
- Bacteria such as Succinivibrio help kangaroos turn hydrogen into acetate instead of methane.
- A 2015 study found kangaroos do emit methane, but at levels closer to horses than to cattle.
- Scientists have tried, with limited success, to transfer kangaroo gut microbes into cattle to cut emissions.
Fun Fact
Australia has half-seriously floated the idea of farming more kangaroos for low-methane meat — a proposal that put marsupial digestion squarely on the national climate agenda.
Sources
- Vendl, C. et al., 'Decreasing methane yield with increasing food intake keeps daily methane emissions constant in two foregut fermenting marsupials', Journal of Experimental Biology, 2015
- Pope, P. B. et al., 'Isolation of Succinivibrionaceae implicated in low methane emissions from Tammar wallabies', Science, 2011