Kangaroos have developed a number of adaptations to a dry, infertile country and highly variable climate. As with all marsupials, the young are born at a very early stage of development – after a gestation of 31–36 days. At this stage, only the forelimbs are somewhat developed, to allow the newborn to climb to the pouch and attach to a teat. In comparison, a human embryo at a similar stage of development would be about seven weeks old, and premature babies born at less than 23 weeks are usually not mature enough to survive. When the joey is born, it is about the size of a lima bean. The joey will usually stay in the pouch for about nine months (180–320 days for the Western Grey) before starting to leave the pouch for small periods of time. It is usually fed by its mother until reaching 18 months.
The female kangaroo is usually pregnant in permanence, except on the day she gives birth; however, she has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch. This is known as diapause, and will occur in times of drought and in areas with poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. In addition, the mother is able to produce two different kinds of milk simultaneously for the newborn and the older joey still in the pouch.
Kangaroos usually have one young annually. The young kangaroo, or joey, is born at a very immature stage when it is only about 2 cm long and weighs less than a gram. Immediately after birth it crawls up the mother's body and enters the pouch. The baby attaches its mouth to one of four teats, which then enlarges to hold the young animal in place. After several weeks, the joey becomes more active and gradually spends more and more time outside the pouch, which it leaves completely between 7 and 10 months of age.
Female kangaroos enter into heat within a few days after giving birth they mate and conceive, but after only one week's development does the microscopic embryo enter a dormant state that lasts until the previous young leaves the pouch.
The development of the second embryo then resumes and proceeds to birth after a gestation period of about 30 days. Kangaroos usually have one young annually. The joey remains in the pouch for nine months and continues to suckle until twelve to seventeen months of age. Kangaroos can have 3 babies at one time.
One becoming mature and just out of the pouch, another developing in the pouch and one embryo in pause mode. There are 4 teats in the pouch and each provides different milk for the different stages of development.
Size: H12cm x L 20cm