What do kangaroos have in their marsupium(pouch)?

"Joey Kangaroo Baby" by Seoulinspired.

Kangaroos are marsupials indigenous to Australia. As kangaroos are marsupials, they have a flexible fold of skin called a pouch or marsupium on their abdomen in which their young ones reside till maturity. This pouch is only present in females and plays a very big role in the safety and nurturing of a joey, especially during the very early days of its life.

Inside the marsupium are present four teats or nipples that supply different types of milk to the joeys. The walls of the pouch are without fur.

A joey inside the marsupium

Courtesy of Reddit user nooyork

The significance of the kangaroo's pouch:

The gestation period of kangaroos is between 21-38 days which is very short for the development of a baby. The joey, at the time of its birth, is highly underdeveloped. So, the joey needs a safe and suitable place to grow until it is capable of living on its own and the marsupium provides it with everything it needs to grow.

The baby is safe inside the marsupium not only from predators but also from bacteria, viruses, and parasites. Another important role of the marsupium is that it provides warmth or a suitable temperature to the joey for its development as the joey is not able to regulate its own body temperature.

For a better understanding of a kangaroo's pouch, watch this video by ScienceInsider.

To see the development of a joey inside the marsupium, click here.