Kangaroos – The 100 Days Project: Day 59 
Digestion: a Glance
Photo: Ray Drew
Pause, for a second, to look at the photograph. Over and over again, as you read accounts of kangaroos, you’ll be told that their characteristic diet is of grasses and forbs. A forb is an herbaceous plant – sometimes, as this young doe seems to think, a wondrous thing.
Kangaroos are herbivores. More specifically, they are grazers.
Macropod metabolic rates decrease as size increases: the larger the macropod the more slowly he/she digests food. Kangaroos, in other words, are the slowest digesters of the macropods, need more time lying about, letting it happen. This affects their diet, in that they can also eat items that take longer to digest. They might love to eat the softest, greenest grass, just as sheep do, but they don’t have to.
Kangaroos are also quasi ruminants.
The larger macropods do not ruminate like sheep and cattle do – do not ‘chew their cud’. The difference is best seen as a matter of balance, or rather a shift in it. Both kangaroos and sheep/cattle digest their grass by a combination of chewing and bacterial fermentation in the gut. In sheep/cattle there is more chewing involved; in the large macropods there is a greater reliance on gut fermentation. Kangaroos, accordingly, do not have the sheep’s four-chambered stomach, but they do have a generous, three-sectioned stomach for fermentation. This is significant in that it appears in some ways to be a more efficient mode of digestion. Sheep and cattle, for example, release something like 250 to 300 litres of methane gas per day as a bi-product of their digestion. Kangaroos, thanks to their particular gut flora, produce none.
I should say something about teeth.
Most kangaroos do not live in areas where they can eat the freshest, softest, greenest, youngest grass. Much of their diet is tougher than that. And the tougher, older, drier grasses are particularly fibrous and abrasive. The kangaroos gut has adjusted to this, as we have seen, and so have their teeth. Kangaroos use most heavily the teeth at the front of their mouths. They do, however, further back on the jaw, have ‘cheek teeth’, four on the left and four on the right. When the front teeth become sufficiently worn, they fall out, and the cheek teeth move along to take their place.
Will kangaroos save the planet?
It has been suggested that kangaroos might save the planet. A rather heavy thing to ask them to do. Methane is one of the worst of the earth’s greenhouse gases, and (see the documentary Cowspiracy) for that reason – i.e. our human predilection for eating so much the flesh of sheep and cattle – one of the greatest contributors to global warming. It has been hypothesied that, if we managed to either (a) replace, by inoculation, the methane-producing gut flora of sheep and cattle with the methane-free gut flora of kangaroos (scientists are working on this even as we speak), or (b) shift from eating the flesh of sheep and cattle to eating the flesh of kangaroos, we might save the planet.
For my money there’s a far better way to save the planet than shifting around our pattern of slaughter or meddling with the gut flora of those we are already slaughtering and abusing, and that is to shift, ourselves, to a plant-based diet.
Oh, and merycism.
Kangaroos may not ruminate, but they do practice merycism (ironically, from the Greek for ‘chewing the cud’): a set of vigorous heavings of the chest and abdomen in order to bring up some of the stomach’s, though less to re-chew it than to provide it with additional saliva to facilitate the fermentation process.
Just in case you notice a roo doing some rather weird things…