Young kangaroos, like young opossums, have been found within the pouch of the mother so firmly attached to the nipples that it is almost impossible to remove them. From this has grown the belief, occasionally encountered, that the young kangaroo is not born as other mammals are, but simply grows from the belly of its mother.
I need hardly say that this belief is not correct. So, how are kangaroos born? Well, kangaroos generally give birth to a premature baby that is as small as a honeybee. Smaller than 1 and a half inches and weighs less than 1 gram baby kangaroo (joey) then finds its way up to the mother’s pouch and enters it. Its strong front legs help it climb up through the body hair of mother kangaroo.
The birth and development of young kangaroo are quite similar to the opossum’s. At birth, the infants do not even faintly resemble the adults, and the young of even the larger species are only about an inch in length. In fact, there is a greater difference in size between the newly born of a large kangaroo and the adult than is to be found in any other mammal.
The grublike young have enlarged claws on the front feet which enable them, like the baby opossums, to scramble through the hair and find their own way into the pouch. The length of time they spend in the pouch varies with the kind of kangaroo and, for the larger species, may be as much as several months.
As the young kangaroo gains in size, it spends less and less time In the pouch, although even when it is quite large. It sometimes bounces into the pouch when danger threatens, or occasionally sticks its head in for a drink of milk.