Bats are the only mammals capable of sustained flight, which often leads to questions about how they manage their young. Bats do not possess an external abdominal pouch for carrying their babies. This confusion likely stems from the fact that bats are nocturnal, flying mammals that care for altricial young. Bats have evolved a different, yet effective, method for transporting and caring for their offspring, which are typically called pups.
Classification: Bats are Placental Mammals
Bats belong to the mammalian order Chiroptera, a group distinctly separate from the marsupials. Their classification as placental mammals dictates their reproductive strategy, which foregoes the need for an external pouch. Placental mammals are characterized by a well-developed placenta that nourishes the fetus internally for a relatively long gestation period.
This prolonged internal development means bat pups are born at a more advanced stage than marsupial young. Marsupials have a brief gestation period and give birth to extremely underdeveloped young, which must complete their growth externally within a pouch. A bat pup is born much larger and more mature relative to its mother’s size, a hallmark of the placental reproductive method.
Physical Mechanisms for Carrying Pups
Since they lack a pouch, bat mothers rely on specialized physical adaptations from both themselves and their pups for transport. Newborn pups possess a powerful grasping reflex and oversized claws on their feet and thumbs. They instinctively use these to cling tightly to the mother’s fur, maintaining a secure hold even while she is in flight.
The mother provides a secure attachment point using her body fur. The pup must latch onto one of the mother’s two nipples, which are usually located in the pectoral region near the armpit, and grip the surrounding fur to remain attached. Some species, like free-tailed bats, utilize the uropatagium—the membrane between the hind legs and tail—to create a temporary cradle during birth or as a brief resting spot.
Carrying the pup during flight is an enormous physical demand, as the newborn can weigh up to one-third of the mother’s weight at birth. Due to this weight strain, many bat species only carry their pups for the first few days or weeks of life. Once the pup can regulate its own body temperature, the mother leaves it safely clustered with other young in a maternity roost while she forages.
Developmental Timeline and Independence
Bat pups undergo a period of rapid development, driven by the need to become flight-capable quickly. Though born altricial—often blind and hairless—they gain strength swiftly while constantly nursing. Their eyes open and fur begins to grow within a few days of birth.
The ability to achieve true powered flight is the biggest milestone and typically occurs between three and six weeks post-birth, depending on the species. This onset of flight is often preceded by practicing “push-ups” and flapping exercises to strengthen the wing muscles.
Weaning, the transition from mother’s milk to a solid diet, often coincides with the pup’s first successful flights. The rapid progression to independent foraging ultimately signals the end of maternal care. By about six to seven weeks, many bat pups are functionally independent.