Kangaroos are a fascinating species for a myriad of reasons, from the way they hop to their extraordinary feats of strength. But, perhaps most fascinating of all is the way they birth and carry their young. Kangaroos are one of a few distinct species that birth and carry their young inside a specialized pouch. Here’s a look at this amazing process.
Marvelous Marsupials
Kangaroos are known for their adorable looks, unique hopping mode of transportation, and of course, being an icon of Australia – the only place they roam wild! But, kangaroos are also known for the extraordinary way they birth and carry their young, which goes back to their marsupial roots.
Marsupials are a group of mammals named for their unique gestation pouch known as the marsupium – the Latin word for pouch. Kangaroos are part of this marsupial group. There are over 250 species of marsupials found around the world, many of them also residing in Australia alongside the kangaroo. Most notably, the kangaroo's “cousins” include the koala, wombat, wallaby, and even the infamous Tasmanian devil.
Throughout history, marsupials have marveled the masses for the unique way they birth and carry their young, leading to all sorts of mythology and folklore. These days much more is known about the marsupial birthing cycle, including that of the famous kangaroo.
The Kangaroo Birthing Cycle
Unlike many other mammals, which tend to breed at specific times of the year due to climate and food scarcity, kangaroos breed year-round. This means it’s possible to see kangaroos with offspring at any time. Much to the delight of Australia’s tourists hoping to spot a joey – the proper name for a baby kangaroo.
The kangaroo birthing cycle is quite unique. Kangaroos are only technically pregnant for around 28 to 32 days, while the embryo is being formed. Once formed, the embryo travels to the pouch and latches on, where it will remain for the next several months. Since there is no placenta, the growing baby kangaroo – known as a joey, will receive all its nutrients by nursing inside its mother’s pouch. This cycle will transform the tiny, jelly bean-sized embryo into a fully developed joey, ready to emerge from the pouch, in about 6 to 8 months.
From Jelly Bean to Joey
During the 6 to 8-month growth cycle, the tiny embryo, which is the size of a jellybean, blind, and hairless, will grow into a full-size joey, weighing around 8 pounds and covered in fur. Exact time frames vary between different kangaroo species.
Around 6 months of age, the joey will start taking short trips out of the pouch, learning how to stand and walk. They will still return to the pouch and continue to nurse for several more months. Between 8 and 9 months, the joey will leave the pouch for good but may still nurse for up to a year while they learn how to graze.
Amazingly, the mother kangaroo can support up to three of her offspring at a time, one joey out of the pouch, one joey in the pouch, and another embryo awaiting the pouch to be vacant. If conditions aren't right or her other joey isn't ready to leave the pouch, she can even put a pause on her pregnancy with a process known as embryonic diapause. It is believed this works by the kangaroo’s body sending signals to increase or decrease certain hormones such as melatonin and prolactin. Once conditions are right, the embryo will be released, and the cycle continues. Another extraordinary feat by these marvelous marsupials!
Leaving The Pouch
Once the joey is out of the pouch, they don’t just go hopping off into the sunset! Joeys will still stay with their mother for the next few years as they grow into adults. After they reach full maturity at around 18 to 24 months, female kangaroos will often stay with their mothers indefinitely. They become permanent members of her mob – the term for a group of kangaroos. They will breed with males from the same mob and continue the cycle of bringing new joeys into the world.
Male kangaroos, on the other hand, will leave their mob once they have reached mating age. They will set out to find a new mate and make their way into a new mob. Once they find a new mob to join, young male kangaroos will then compete with other males for breeding rights, but it's unlikely many of the new members will win. Kangaroo mobs operate on a social hierarchy with alpha males and established breeding practices. It can take years for a new mob member to reach alpha status and breed, but once they do, the extraordinary kangaroo birthing cycle begins again!
