Britannica Sources used in this answer

How do kangaroos reproduce differently from placental mammals?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Red kangaroos on the move — kangaroo A group of red kangaroos (*Macropus rufus*) using their powerful hind legs and feet to hop.

Kangaroos reproduce differently from placental mammals primarily due to their lack of a specialized uterine wall for embryo implantation and their significantly shorter gestation period. While placental mammals utilize a complex placenta to nourish the fetus for an extended period within the womb, kangaroos give birth to highly immature young, known as a joey, after only about 30 days of development.1234

Following birth, the joey must crawl to the mother's marsupium (pouch), where it attaches to a teat to complete its development. This process highlights several key reproductive adaptations:32

Embryonic Diapause: Many kangaroo species can pause the development of a new embryo while an older joey is still in the pouch, allowing them to time births with favorable environmental conditions.3
Lactation: During periods when a mother is nursing young at different developmental stages, her teats can produce milk of varying compositions to meet the specific needs of each joey.3
Developmental Site: Unlike placental mammals, which complete the majority of fetal growth internally, kangaroos rely on the pouch as the primary site for the latter stages of development.12