The Wild Reality Behind Kangaroo Pregnancy

Kangaroos and their baby joeys are quite adorable, but the way they develop is frankly a little disconcerting. We humans have a specific idea of what pregnancy and birth entails, but kangaroos and all their fellow marsupials have a very different experience indeed. And really, it can seem almost alien to us.

Lords of Australia

There’s a wide range of marsupials, and most of them live in Australia. In addition to kangaroos, the group in this country includes wombats, Tasmanian devils, and koalas. They’re less dominant in other parts of the world, though, with opossums being the only native marsupials of the North American continent still alive today.

Changing fortunes

Yet long ago, marsupials were really common, even across North America. Here, in fact, they used to outnumber “placental” mammals – an extremely broad category including whales, shrews, dogs, cats, cows, sheep, and yes, even humans. So there was indeed a time when we were the "weird" ones.

Different strokes

There are plenty of similarities between marsupials and their placental mammal counterparts. The two kinds of animals both have hair, for instance, and species from each group bring up their own babies, a parenting strategy which stands in stark contrast to most reptiles. But really, it’s the differences between the two types of mammals where things get interesting.

Bun in the oven

The most distinctive characteristic of marsupials – and kangaroos, by extension – centers around their pregnancies and the development of their young. Sure, both they and the placental mammals nourish their babies with milk and take care of them until they’re older. But there’s also a crazy difference at play in the process.

Big foot

Whichever way you look at it, kangaroos are fascinating creatures with so many interesting quirks. They belong to the Macropodidae family, which consists of 67 species that live across Australia and the nearby island of New Guinea. The Latinate family name actually derives from the Greek for “big foot,” which is quite telling.

Hopping mad

Kangaroos do, indeed, have massive feet and a pair of remarkably strong back legs. These limbs can propel the beasts at great speeds: believe it or not, roos have been clocked at about 35mph. Of course, they’re not exactly sprinters; rather, they move by means of their trademark hops. In just one leap, kangaroos can soar further than 25 feet.

The long tail

It’s not just the robust and athletic legs that allow kangaroos to hop such great distances at these incredible speeds. Their lengthy, muscle-clad tails are also pivotal here. In fact, British newspaper The Guardian reported that recent research suggests the tail actually does more work in propelling kangaroos than all their other limbs combined.

Swimming for it

And as if the tail wasn’t amazing enough already, it turns out that it plays another important role for kangaroos. Though it’s not immediately obvious to most people, the truth is that kangaroos are actually really good in the water. And the tail really helps when they’re swimming, which they might do to get away from predators.

Security alarms

When on land, kangaroos have other ways of dealing with the presence of predators. They tend to live in troops of about 50 members, and if they feel threatened by a hungry-looking visitor, they’ll start banging the ground beneath them with their enormous feet. This alerts everyone in the group that there’s – ahem – danger afoot.

Sounding off

If they’re stressed out, kangaroos might also make a sort of hissing sound, or a growl. They can make a range of different noises for different scenarios, in fact. Females can produce a sort of clicking to speak with their babies, while the males can erupt in something close to a chuckling noise when they’re trying to woo females.

Boxing kangaroos

If push comes to shove, kangaroos can be fearsome combatants. They can throw some extremely forceful kicks and slaps, and they’re not afraid of biting if necessary. Of course, these fighting moves are often deployed against each other, such as when males start battling it out to win a mate’s affections.

All in the family

You might be aware of smaller versions of kangaroos hopping around the place; these are known as wallabies and wallaroos. All these animals belong to the Macropodidae family, with kangaroos simply being the biggest members of the group. There are four species of kangaroo specifically: the red, the antilopine, the eastern gray, and the western gray, all of which share the same pregnancy quirk.

True colors

Aside from their big feet and tails, all these types of kangaroo are known for their highly attuned senses of sight and sound. They all have short fur on their bodies, too, though the colors can vary across the species. We obviously have red and gray ones, but there are also kangaroos in different shades of brown.

A wide spread

The different species of kangaroo can generally be found in different parts of Australia. It should go without saying in which parts of the country the eastern and western grays tend to reside. The reds, meanwhile, can be found throughout the open plains of the whole country, while the antilopines stick to the north.

Dwindling numbers

Generally speaking, kangaroos and their smaller counterparts are doing well across Australia. For the time being, at least, most species are maintaining healthy numbers and their populations continue to thrive. Having said that, the numbers of the antilopine species are beginning to dwindle, as are those of the black wallaroo.

The Aboriginal connection

Kangaroos are hugely significant for Australia’s Aboriginal population. The marsupials hold a special place within these people’s culture and spirituality, but they’ve also been useful in a more practical sense. The animals have traditionally served as an important source of food, plus their hides have provided a useful material for making clothes.

Going forward

The modern nation of Australia also considers the kangaroo to be a significant symbol. It can be seen in the country’s coat of arms, ostensibly because the animal is incapable of traveling backwards. This, the thinking goes, is a good symbol for a nation keen to keep making forward progress.

On the menu

Kangaroos undoubtedly occupy a special place in Australian culture, but life in the country isn’t always straightforward for the marsupials. They don’t have a huge number of predators, but humans, dingoes and even eagles have all been known to strike them. Even fellow herbivores can harm kangaroos, if they eat up all the vegetation they need to survive.

A wishing well

Another pressing concern for kangaroos relates, understandably, to water. Like all of us, they need it to stay alive, which can sometimes be a challenge in an environment like Australia’s. The animals prefer to drink from open sources, but if things get desperate then they might dig to find water underground.

Eating like a cow

Kangaroos tend to be at their hoppiest as night falls and fades, when the heat of the sun isn’t an issue. They’ll spend much of their time searching for food, which tends to consist of grasses, flowers, leaves and fruit. The way they eat is reminiscent of cows, as they actually regurgitate their meal, chew it a second time, and then let it travel through the chambers of their bellies.

The pouch

Perhaps the most famous feature of the kangaroo, of course, is the pouch that a female has on her front. From our early days watching cartoons as children, many of us are familiar with the image of a baby joey sticking out of its mother’s pouch. But what’s actually the purpose of this thing, and how does it work? The truth, it turns out, is wild.

Home sweet home

A kangaroo’s pouch plays a crucial role in the development of a young member of the species. Basically, when a joey is born, it’s unrecognizable from the animal it will one day grow up to be. The pouch, then, is where the baby will instinctively navigate to immediately after its birth and where it will grow and develop.

A short pregnancy

Female kangaroos are only actually pregnant for a really short period of time: gestation generally lasts between three and five weeks. Then, the whole process takes a different turn that’s totally unrecognizable to the experience of humans and our fellow placental mammals.

Tiny joey

After the period of pregnancy, the female kangaroo will give birth to a tiny joey. And it really is tiny, measuring less than 1 inch long. Joeys the size of mere rice grains aren’t unheard of, but even at their largest they won’t be much bigger than a honey bee.

A difficult crawl

The joey is extremely undeveloped at this early stage, unable to see or do much. It does, however, have little limbs. And somehow, driven by instinct, it finds the strength to pull itself towards its mother’s pouch. There it will remain as it grows and develops to the point of being strong enough to survive in the world beyond.

Safe space

The pouch doesn’t have much hair inside, but it’s certainly warm enough to sustain the joey. The opening is situated at the top, so the baby kangaroo won’t accidentally slip out too early. It needs to stay inside to gather its strength, which it does by drinking its mother’s milk.

Spoilt for choice

Female kangaroos have four nipples inside the pouch onto which their offspring can latch. Each of these provides milk that contains a different level of nutrients compared to the other three. So, as the joey grows up, it will consume the milk most appropriate for its present stage of development.

Working mom

As if that wasn’t already amazing enough, a mother can also feed three joeys at the same time. And we’re not just talking about offspring of the same age. Babies at varying stages of development can actually be sustained by their mother, with her different milks providing different benefits for each one.

Nourishing the young

Newborns, for instance, will be given milk that’s high in protein but isn’t inundated with carbs. When they get older, they’ll move onto milk that’s higher in carbs and which contains a little fat, too. Finally, joeys that are getting ready for the world are provided with milk containing lots of fat and protein, but fewer carbohydrates.

Another round

There’s another amazing quirk of kangaroo pregnancy to think about. As soon as a female has given birth to her tiny, rice-sized joey, she’s perfectly capable of mating again. If she conceives, though, this second joey won’t be born after a month. Instead, it will develop into a collection of roughly 100 cells — and then it stops.

Pressing pause

This basic collection of cells will then remain inside the female kangaroo’s body, but the pregnancy won’t progress any further for a while. In other words, the mother has pressed pause on the growth and development of her second baby. This remarkable phenomenon is known by the term “embryonic diapause.”

Waiting it out

Embryonic diapause is possible because kangaroos and wallabies don’t just have one uterus, but two. The undeveloped embryo will wait in one, while its sibling grows in the other and then moves into the pouch. When the older one is ready and strong enough, the younger one will then be able to begin its development.

Quick visits

It takes quite a bit of time for a joey to develop to the point of being able to exit the pouch for the first time. Even then, though, it’ll only take sporadic visits to the wider world beyond its mother’s bespoke carry pocket. When it gets hungry, then, it’ll hop right back inside...if it's clean, that is.

Keeping things clean

The joey spends an awful lot of time in its mother’s pouch. Naturally, a lot of mess and dirt can accumulate during that time, so the mother will take responsibility for cleaning. She uses her tongue to keep things sparkling in there. And if her joey’s old enough, she’ll remove it during the process.

At their own pace

Depending on the species, it takes different periods of time for joeys to leave the pouch for good. Red kangaroos, for instance, are pretty quick and will exit at about eight months, though they’ll still consume their mother’s milk for a few months more. Gray kangaroos, meanwhile, will depart after 11 months or so.

Fall back!

A kangaroo’s pouch is a truly remarkable feature that aids the early development of its young. But it has other uses, too. Even if the joey is old enough to leave the pouch, it still serves to protect them when necessary. If there’s danger in the vicinity, the mother will call to the joey and it will hop right inside.

A place to relax

The pouch itself is really adaptable, too, depending on the situation. If things are all good and relaxed, it’s quite flexible and billowy. This means the joey will have plenty of room to stretch out. But if there’s an urgency to the scenario, the pouch is quite a different place for the baby.

Tight space

If the mother needs to flee the scene because of a threat, she stuffs her joey into the pouch. Then, as she hops away, her muscles constrict and the pouch becomes extremely tight. This means that her young offspring isn’t going to just fall out during the escape — and kangaroos often find themselves having to escape, especially recently.