Kangaroos are plant-eaters, and the big species that hop across open country live mostly on grass. They are fussier than they look, choosing particular plants and passing over others that grow all around them.1Australian Mammalogy. Diets and foraging behaviour of red and eastern grey kangaroos in arid shrub land: is feeding behaviour involved in the range expansion of the eastern grey kangaroo into the arid zone? What makes them remarkable is the gut that handles this food, which works much like a cow’s yet releases only a fraction of the methane.2PubMed. Comparative methane production in mammalian herbivores
Grass First, Then Herbs and Shrubs
Grass is the staple of the red kangaroo, the largest species.3Journal of Arid Environments. Diets of mammalian herbivores in Australian arid shrublands: seasonal effects on overlap between red kangaroos, sheep and rabbits and on dietary niche breadths and electivities In wet seasons it also eats many of the soft herbs and wildflowers that spring up after rain.4Journal of Arid Environments. Diets of mammalian herbivores in Australian arid shrublands: seasonal effects on overlap between red kangaroos, sheep and rabbits and on dietary niche breadths and electivities In dry seasons it adds some shrubs to the mix.5Journal of Arid Environments. Diets of mammalian herbivores in Australian arid shrublands: seasonal effects on overlap between red kangaroos, sheep and rabbits and on dietary niche breadths and electivities But in severe drought grass makes up almost 90% of what it eats.6Journal of Arid Environments. Diets of mammalian herbivores in Australian arid shrublands: seasonal effects on overlap between red kangaroos, sheep and rabbits and on dietary niche breadths and electivities
Most kangaroos feed in the cooler hours: early morning, evening and night. They crop low grass close to the ground with their front teeth, and they favour green shoots over dry stalks. Young regrowth is higher in protein and easier to break down than old stalks, so kangaroos often seek out fresh shoots after rain or on mown ground.
That is why mobs gather on green lawns, golf courses and road verges. These spots catch runoff and get mowed, so they offer constant short green growth even when the surrounding country is dry.
Meanwhile, kangaroos ignore plants that are everywhere. They avoid saltbushes and bluebushes, shrubs that are often the most abundant plants in dry country.7Australian Mammalogy. Diets and foraging behaviour of red and eastern grey kangaroos in arid shrub land: is feeding behaviour involved in the range expansion of the eastern grey kangaroo into the arid zone? They also largely avoid eating trees, though red kangaroos do pick certain herbs and small mallow-family shrubs.8Australian Mammalogy. Diets and foraging behaviour of red and eastern grey kangaroos in arid shrub land: is feeding behaviour involved in the range expansion of the eastern grey kangaroo into the arid zone?
How Diets Differ Between Kangaroo Species
Red and eastern grey kangaroos living in the same dry shrubland share 81 to 87% of their diet.9Australian Mammalogy. Diets and foraging behaviour of red and eastern grey kangaroos in arid shrub land: is feeding behaviour involved in the range expansion of the eastern grey kangaroo into the arid zone? Still, eastern greys prefer grass even more strongly than reds, because they have a larger front stomach suited to grass.10Australian Mammalogy. Diets and foraging behaviour of red and eastern grey kangaroos in arid shrub land: is feeding behaviour involved in the range expansion of the eastern grey kangaroo into the arid zone?
Euros, a stocky hill kangaroo, keep eating grass even when little is left.11Wildlife Research. Seasonal Changes in Diet Preferences of Free-Ranging Red Kangaroos, Euros and Sheep in Western New South Wales They live in rocky, hilly country where food is sparse.
Among kangaroos and wallabies more broadly, grazers eat mostly grass, while browsers eat the leaves and shoots of shrubs. Many smaller wallabies and pademelons are browsers. Browsers cope better with bitter plant chemicals called tannins, and in one test a tannin cut digestion most in a grass-eating wallaby and least in a browsing pademelon.
Tree-kangaroos are leaf-eaters. Lumholtz’s tree-kangaroo eats leaves from many rainforest trees but favours some far more than others.12Australian Mammalogy. Studying food preferences in captive cryptic folivores can assist in conservation planning: the case of the Lumholtz’s tree-kangaroo (Dendrolagus lumholtzi) Leaves are low in energy, and tree-kangaroos burn only about 60% of the energy expected for an animal their size.13PubMed Central. Balancing the scales: Preliminary investigation of total energy expenditure and daily metabolizable energy intake in Matschie’s tree kangaroo (Dendrolagus matschiei) That slow, low-energy lifestyle lets them live on poor food.
Inside the Kangaroo Stomach
In kangaroos, microbes in the stomach break down plant food before it reaches the intestines.14PubMed. Macropod nutrition The stomach has a sac-like front section, a long tube-shaped section, and a final digestive section.15Journal of Advanced Veterinary and Animal Research. Morphological and morphometric characteristics of gastric mucosa in western grey kangaroo (Macropus fuliginosus) This layout mixes fibrous grass thoroughly with the microbes.16Journal of Advanced Veterinary and Animal Research. Morphological and morphometric characteristics of gastric mucosa in western grey kangaroo (Macropus fuliginosus)
Food goes first into the sac-like front section, where fermentation begins. It then moves along the long tube-shaped section, where fermentation continues as the food is slowly pushed along. The final section works more like a normal stomach, so the food reaches the intestines already partly broken down.
Kangaroos cannot digest plant fibre with their own enzymes. The bacteria do the work, and the animal absorbs the fatty acids and other products that result. The microbes themselves are also digested further along, so the kangaroo gets protein from them as well as from the plants.
The microbes are unlike a cow’s. Two big groups of bacteria make up more than 90% of the microbes in a kangaroo’s front stomach.17PubMed Central. Shedding Light on the Microbial Community of the Macropod Foregut Using 454-Amplicon Pyrosequencing Kangaroo relatives such as the tammar wallaby carry bacterial lineages found nowhere else.18PubMed Central. Adaptation to herbivory by the Tammar wallaby includes bacterial and glycoside hydrolase profiles different from other herbivores Kangaroos reached cow-like digestion with their own distinct toolkit of microbes and enzymes.19PubMed Central. Adaptation to herbivory by the Tammar wallaby includes bacterial and glycoside hydrolase profiles different from other herbivores
Kangaroos do occasionally bring food back up and rechew it. This is not cud-chewing in the cow sense: it happens irregularly, the animal can look distressed, and they don’t need it to digest. So kangaroos are not ruminants even though their digestion is similar.
For the same amount of food, kangaroos release much less methane than cattle or sheep.20bioRxiv. Metagenomic analysis of marsupial gut microbiomes provides a genetic basis for the low methane economy Their gut bacteria use the hydrogen that would otherwise become methane.21bioRxiv. Metagenomic analysis of marsupial gut microbiomes provides a genetic basis for the low methane economy Scientists study these microbes to cut methane from livestock.22bioRxiv. Metagenomic analysis of marsupial gut microbiomes provides a genetic basis for the low methane economy
Teeth That Keep Moving Forward
Grass quickly wears teeth down.23The Conversation. Kangaroo teeth grow forever – and keep a record of their owner’s age and sex Grass blades contain tiny hard particles of silica, and soil and dust on the leaves add grit, so every mouthful grinds. Kangaroos feed close to the ground, so they take in more grit than an animal eating leaves higher up.
Their answer is a conveyor belt. Kangaroo molars slowly shift forward in the jaw, and worn ones fall out at the front to make way for fresh ones behind.24The Conversation. Kangaroo teeth grow forever – and keep a record of their owner’s age and sex A young kangaroo has its first molars in front, and new ones emerge at the back as the front ones wear away. This gives fresh grinding surfaces for many years, much longer than a single set could last. Kangaroos also evolved thick enamel on their molars to resist grinding wear as their diets became grassier.25PubMed. Contingent evolution of thick enamel by kangaroos to resist dietary abrasion
But the supply runs out, and the oldest kangaroos have only a couple of teeth left.26The Conversation. Kangaroo teeth grow forever – and keep a record of their owner’s age and sex Once the last molars wear down, chewing grass becomes hard, and poor chewing means less nutrition from each meal. Tooth wear is also one way researchers estimate a kangaroo’s age.27The Conversation. Kangaroo teeth grow forever – and keep a record of their owner’s age and sex
Surviving Drought and Little Water
Kangaroos use water slowly and can survive losing weight during dehydration.28Mammal Review. The biology of kangaroos (Marsupialia‐Macropodidae) Desert kangaroos cut the water lost through sweat-like evaporation, urine and droppings when dry.29Mammal Review. The biology of kangaroos (Marsupialia‐Macropodidae) They also recycle urea, a waste product, back into the gut so microbes can turn it into protein.30Mammal Review. The biology of kangaroos (Marsupialia‐Macropodidae) The microbes use its nitrogen to build protein, which the animal can then digest, so the waste becomes food. This matters most when the diet is poor in protein, as it is in dry times.
When water is restricted, the share of urea broken down in the gut rises from 68% to 76%.31PubMed. Effects of water restriction on digestive function in two macropodid marsupials from divergent habitats and the feral goat Less urine is then needed to clear waste, which saves water.
That helps explain why kangaroos can go long periods without drinking when green feed is available. Much of their water comes from green plants, and feeding at night, when plants hold dew, adds moisture. Resting in shade by day saves more. In drought they still visit dams and troughs.
Some kangaroos also eat soil at natural licks.32Journal of Mammalogy. Facultative geophagy at natural licks in an Australian marsupial Those licks are richer in sodium, magnesium and sulfur than nearby soil.33Journal of Mammalogy. Facultative geophagy at natural licks in an Australian marsupial Not all populations do it, and it matters most in hot, low-salt regions.34Journal of Mammalogy. Facultative geophagy at natural licks in an Australian marsupial
Kangaroos, Livestock and the Land
Red kangaroos and sheep share 58 to 73% of their diet in normal pasture.35Australian Journal of Ecology. The dietary overlap between red kangaroos (<i>Macropus rufus</i>) and sheep (<i>Ovis aries</i>) in the arid rangelands of Australia In dry times both eat more shrubs and overlap drops to 52 to 66%.36Australian Journal of Ecology. The dietary overlap between red kangaroos (<i>Macropus rufus</i>) and sheep (<i>Ovis aries</i>) in the arid rangelands of Australia Sharing food doesn’t mean the animals take it from each other, since in good seasons there is plenty of grass for both. Overlap turns into competition only when the shared food runs short.
That happens mainly in near-drought, when kangaroos crowd in from surrounding land.37Australian Journal of Ecology. Competition between red kangaroos (<i>Macropus rufus</i>) and sheep (<i>Ovis aries</i>) in the arid rangelands of Australia As that land dries out, kangaroos move onto pasture that still has some green growth, and sheep and kangaroos draw on the same limited food. Sheep then lose weight, while kangaroos keep their condition.38Australian Journal of Ecology. Competition between red kangaroos (<i>Macropus rufus</i>) and sheep (<i>Ovis aries</i>) in the arid rangelands of Australia
Heavy grazing affects the land too. Kangaroo grazing can reduce grass, pack the soil and slow rain soaking in.39Journal of Arid Environments. Impacts of grazing by kangaroos and rabbits on vegetation and soils in a semi-arid conservation reserve High numbers of eastern greys harmed other wildlife in Canberra reserves.40Environment, Planning and Sustainable Development Directorate. ACT conservation research: the effects of kangaroo grazing on biodiversity Managers there aim for about 1 kangaroo per hectare in grassland and fewer in forest.41Environment, Planning and Sustainable Development Directorate. ACT conservation research: the effects of kangaroo grazing on biodiversity
Farmers see kangaroos eating pasture meant for stock, while studies show competition is intermittent, not constant. Removing livestock water points and fences changes where kangaroos graze, and population control is debated on both welfare and ecological grounds.
What Joeys Eat
A newborn joey, the name for a young kangaroo in the pouch, attaches to a teat and drinks milk for months. It then starts nibbling grass while still returning to the pouch to drink. Its stomach microbes must be established as it begins eating plants, so the switch cannot happen all at once. Mothers can even produce different milk for joeys of different ages.
A young kangaroo that has left the pouch is still moving from milk to plants.42PubMed. How important is milk for near-weaned red kangaroos (Macropus rufus) fed different forages? These young kangaroos die in the largest numbers during drought.43PubMed. How important is milk for near-weaned red kangaroos (Macropus rufus) fed different forages? They are small and still developing their digestion, and drought leaves mostly coarse, dry plants. Adults can get by on poor food, but a young one that has lost its milk supply and cannot digest coarse feed can starve.
Young kangaroos digest only about 36% of coarse, high-fibre hay versus about 55% of leafy lucerne.44PubMed. How important is milk for near-weaned red kangaroos (Macropus rufus) fed different forages? On coarse hay they lost weight even with milk, while on lucerne they grew about 45 g a day.45PubMed. How important is milk for near-weaned red kangaroos (Macropus rufus) fed different forages?
Feeding Kangaroos in Captivity and the Wild
Zoos and carers usually give grass hay plus pellets. Most kangaroo pellets start as rabbit pellets with added vitamin E and selenium.46Merck Veterinary Manual. Nutrition in Marsupials – Management and Nutrition These additions help prevent lumpy jaw, a serious jaw infection in captive kangaroos.47Merck Veterinary Manual. Nutrition in Marsupials – Management and Nutrition Captive animals don’t eat the variety of wild plants, so pellets supply nutrients that hay alone might lack.
Wild kangaroos are a different matter. Bread, carrots and processed food don’t suit a grass-fermenting gut. A kangaroo may eat bread eagerly because it is easy, but its microbes are adapted to fibre, so the food can upset digestion. The harm builds over repeated feeding, and the animal may come to rely on handouts instead of grazing. Handouts also draw kangaroos to roads and people, raising the risk of injury. At wildlife parks, use only the approved feed sold on site.
If you find an orphaned joey, don’t give it cow’s milk. Keep it warm and quiet, and contact a local wildlife rescue group straight away.