Final answer:
The behavior that predicts birth in mammals varies depending on their category: monotremes lay eggs, marsupials give birth to immature young that develop in a pouch, and placental mammals give birth to more developed offspring thanks to the placenta.
Step-by-step explanation:
The behavior that predicts birth in mammals is based on their method of reproduction. There are three types of mammals characterized by their reproduction: monotremes, marsupials, and placental mammals. Monotremes, like the platypus and echidnas, lay eggs, which is an exceptional case in mammal reproduction. Marsupials, such as kangaroos and koalas, give birth to underdeveloped embryos that continue their development in the mother's pouch. Lastly, placental mammals, which include a wide range of species from humans to whales, give birth to relatively larger and more mature fetuses thanks to the placenta that nourishes the fetus during a longer developmental period inside the womb.
Marsupial reproduction is unique in that the offspring, typically called a joey, is born at a very immature stage of development. The newborn crawls into the mother's pouch, where it attaches to a nipple and finishes its development. In contrast, placental mammal offspring are nurtured inside the mother's uterus and are born at a more advanced stage of development due to the presence of the placenta, which allows a longer gestation period for growth.