Flight, the ability to move through the air, represents a remarkable adaptation in the animal kingdom. While many creatures navigate terrestrial or aquatic environments, a select few mammals have evolved mechanisms for aerial locomotion. True flight involves powered movement, where an animal actively generates both lift to counteract gravity and thrust to move forward through the air. This form of movement is a rare trait among mammals.
The Mammal That Truly Flies
Bats are the only mammals capable of sustained, powered flight. Their unique anatomy allows for active flapping, which generates the necessary lift and thrust. Over 1,300 species of bats inhabit diverse environments worldwide.
The wings of a bat are highly modified forelimbs, featuring elongated finger bones that support a thin, flexible membrane called the patagium. This membrane stretches between their body, long fingers, legs, and often their tail. The patagium is crisscrossed with tiny blood vessels and elastic fibers, allowing bats to precisely control their wing shape during flight.
For a bat to fly, it must generate both lift to stay airborne and thrust to move forward. The large membrane between the bat’s body and its fifth finger provides significant support and lift, while the membranes between the elongated fingers are crucial for generating forward thrust. Powerful muscles in their chest and back facilitate the rapid flapping motion, enabling bats to ascend, descend, and change direction with agility.
The bat’s wing structure allows for adjustments in shape and angle during each wingbeat. This flexibility enables them to vary the amount of lift and thrust generated. Their specialized skeletal system, including lightweight and hollow bones, contributes to efficient flight.
Mammals That Glide
While bats achieve true powered flight, other mammals exhibit a form of aerial locomotion known as gliding. Gliding differs from true flight because it involves a controlled descent rather than sustained, active propulsion. These animals launch themselves from an elevated point and use specialized membranes to slow their fall and travel horizontally.
Mammals such as flying squirrels, sugar gliders, and colugos (often called “flying lemurs”) are examples of gliders. Despite their names, these animals do not flap to generate lift or thrust for sustained flight. Instead, they possess a fur-covered patagium, which stretches between their limbs.
When these mammals leap from a tree, they extend their limbs, spreading the patagium to create a parachute-like surface. This membrane catches air, allowing them to control their descent and steer by adjusting the tension and angle of their body and tail. Flying squirrels, for instance, use their flattened tail as a rudder and stabilizer during their glides.
Sugar gliders have a patagium that extends from their fifth forefinger to their ankle, enabling glides of up to 45 meters. Colugos are well adapted for gliding, with a patagium that is proportionally the largest, extending from their neck to their fingers, toes, and even the tip of their tail. This extensive membrane allows them to glide efficiently between trees, covering distances of up to 70 to 150 meters with minimal altitude loss.