Kangaroos are marsupials known for their unique way of rearing young. Female kangaroos have a specialized abdominal pouch, called a marsupium, which protects and nurtures their offspring. This pouch provides a safe haven where undeveloped young can grow and mature. It functions as a mobile incubator, offering warmth, security, and constant nourishment for their long developmental period.
The Joey’s First Trek
Kangaroo birth is unique due to the newborn’s underdeveloped state. After a gestation of about 33 days, the mother gives birth to a tiny, hairless, and blind joey, typically no larger than a jelly bean, measuring around 2 centimeters and weighing less than a gram. Despite its embryonic appearance, this minuscule joey has an innate sense of smell and strong forelimbs, which it uses to begin its journey immediately after birth.
The mother licks a path through her fur from the birth canal to her pouch, guiding the joey. The joey then instinctively crawls, using a swimming motion with its forelimbs, through the fur and into the pouch, a trek that takes about three minutes. Once inside, it firmly attaches itself to one of the mother’s nipples, where it will remain for its development.
Growth and Change Inside the Pouch
Inside the warm, protected environment of the pouch, which maintains a temperature of about 105 degrees Fahrenheit (40.5 degrees Celsius), the joey undergoes significant development. Initially, its muscles are too weak to suckle, so the mother’s nipple expands in the joey’s mouth, releasing milk directly. The pouch is hairless inside and lined with sweat glands that secrete an antimicrobial substance, protecting the joey from infections.
The mother’s milk composition changes to meet the joey’s evolving nutritional needs. Early milk is rich in carbohydrates and water, providing hydration and energy, along with antibodies for the joey’s underdeveloped immune system. As the joey matures, the milk becomes richer in protein and fat, supporting muscle development and growth, while carbohydrate content decreases. Female kangaroos can even produce different types of milk from different nipples simultaneously, catering to joeys of varying ages.
The Path to Independence
The duration a baby kangaroo stays in the pouch varies by species, but a joey resides there for about 6 to 11 months. Red kangaroos remain in the pouch for around 6 to 8 months, while grey kangaroos may stay for up to 11 months. The process of leaving the pouch is gradual, not sudden.
Around 6 to 7 months of age, the joey begins to tentatively poke its head out, taking short exploratory trips outside the pouch. These initial excursions are brief, lasting only a few minutes and staying close to the mother. The joey often retreats back into the pouch for safety, warmth, and continued feeding. Even after fully emerging, joeys continue to suckle from their mother for several more months, gradually transitioning to grazing. Weaning typically concludes around 12 months, although it can extend up to two years depending on the species and individual circumstances.