Only one group of mammals is capable of sustained, powered flight. This unique evolutionary path sets them apart from all other mammalian species.
The Mammalian Aviators
Bats, belonging to the order Chiroptera, are the only mammals that have evolved true, powered flight. Their name, “Chiroptera,” translates to “hand-wing,” referencing their specialized anatomy. With over 1,400 recognized species, bats represent a significant portion of all mammalian species, making them the second most diverse order after rodents.
These mammals inhabit nearly every corner of the globe, thriving in diverse climates from tropical to temperate regions, spanning all continents except Antarctica and some isolated oceanic islands. Bats play important roles in ecosystems, pollinating various plants, dispersing seeds, and controlling insect populations. Some bats are the sole pollinators for plants like agave, crucial for tequila production, and they consume large quantities of agricultural pests.
The Mechanics of Bat Flight
Bats achieve powered flight through highly specialized anatomical adaptations, particularly in their wings. A bat’s wing is a modified forelimb where the finger bones are significantly elongated. These elongated digits support a thin, elastic membrane of skin called the patagium, which stretches between the fingers and extends to the body and hind limbs. This flexible structure allows bats to precisely control their wing shape, enabling remarkable maneuverability, including hovering and sharp turns.
The patagium itself is divided into several regions: the propatagium along the leading edge, the dactylopatagium between the digits, the plagiopatagium connecting the last digit to the hindlimbs, and often a uropatagium that includes the tail. Powerful chest muscles, notably the pectoralis, drive the wing’s downstroke, similar to birds. Tiny muscles embedded within the wing membrane allow bats to fine-tune the stiffness and curvature of their wings during flight, providing exceptional control not seen in birds, whose wings are primarily supported by feathers.
Beyond True Flight: Gliding Mammals
While bats are the only mammals capable of true, powered flight, other mammals possess adaptations for aerial locomotion known as gliding. Gliding differs from powered flight as it relies on gravity and air resistance for movement, lacking continuous thrust or active muscle-powered lift. These animals launch themselves from a height and use specialized membranes to slow their descent and travel horizontally.
Examples of gliding mammals include flying squirrels, sugar gliders, and colugos, often called “flying lemurs” despite not being true lemurs. These animals typically have a patagium, a furred skin membrane that extends between their limbs. In flying squirrels, this membrane stretches from wrist to ankle, allowing them to glide impressive distances between trees. Colugos are particularly adept gliders, with a patagium that extends from their face to their claws and tail, enabling glides of over 100 meters with minimal height loss.