A joey is the term for a baby kangaroo. Kangaroos exhibit a unique reproductive strategy where their young are born in an extremely underdeveloped state after a short gestation period, typically 30 to 40 days. This requires continued development within a specialized external pouch on the mother’s abdomen, a defining characteristic of marsupials.
Life Inside the Pouch
A newborn joey is remarkably small, often compared to the size of a jelly bean, measuring around two centimeters (one inch) long and weighing less than a gram. It is born hairless, blind, and with undeveloped hind limbs, yet its forelimbs are strong and well-formed. Immediately after birth, guided by instinct and its sense of smell, the joey begins an arduous, unassisted climb through its mother’s fur towards the pouch. The mother may lick a path to facilitate this journey, which is typically completed in under three minutes.
Once inside the warm, protective pouch, the joey firmly latches onto one of the mother’s teats. This teat then swells, securing the joey in place for several months as it continues its rapid development. The pouch provides a sterile, incubator-like space, maintaining a consistent temperature, often around 40.5 degrees Celsius (105 degrees Fahrenheit). The mother regularly cleans the pouch by inserting her muzzle and licking, ensuring a hygienic environment for her developing offspring.
Over the following months, the joey undergoes significant physical changes within the pouch. Its fur begins to grow, its eyes open, and its limbs strengthen, gradually taking on the appearance of a miniature kangaroo. The duration a joey spends continuously inside the pouch varies by species, but it is typically at least six months. For example, red kangaroo joeys remain in the pouch for about six months, while grey kangaroo joeys may stay up to eleven months before peeking out.
Growing Up and Leaving the Pouch
After several months of development, the joey begins its cautious introduction to the outside world, often around six months of age. These initial excursions are brief and tentative, lasting only a few minutes, with the joey quickly retreating back into the safety of the pouch if startled or needing comfort. The mother often facilitates these first ventures, sometimes relaxing her pouch muscles to allow the joey to tumble out and practice its movements.
During this transitional period, the joey gradually begins to supplement its milk diet by nibbling on grass and other vegetation. Kangaroos can produce different types of milk simultaneously from different teats, catering to the specific nutritional needs of joeys at various stages of development. Even as it explores outside, the joey continues to return to the pouch for nourishment, warmth, and protection, especially during rest or perceived danger.
As the joey grows larger and becomes more confident, it spends increasing amounts of time outside the pouch. Eventually, it reaches a size where it can no longer comfortably fit inside, typically between eight and twelve months of age, though this varies by species. At this point, the mother may even discourage the joey from re-entering the pouch. Full independence, where the joey no longer relies on the pouch or its mother’s milk, generally occurs between twelve and eighteen months, with red kangaroos often achieving independence around twelve months and grey kangaroos taking slightly longer.