Bats are unique among mammals as the only group capable of sustained, powered flight. This specialization often leads to the assumption that they are clumsy and helpless on the ground. While this is true for the vast majority of species, a few highly specialized bats have evolved the ability to walk and even run effectively. This terrestrial ability is not a random trait but a specific adaptation driven by unusual foraging needs, requiring a complete overhaul of standard bat anatomy and movement mechanics.
The General Rule: Why Bats Prefer Flight
The anatomy of most bats is optimized almost entirely for flight, making terrestrial movement extremely awkward. The forelimbs are fundamentally wings, with elongated finger bones supporting the thin, delicate patagium membrane. This structure is fragile and poorly suited for bearing the full body weight or navigating rough terrain, meaning most bats rely on a clumsy shuffle if they find themselves grounded.
The hind limbs also present a significant obstacle to walking. They are slender, lightweight, and rotated at the hip joint. Unlike the forward-facing knees of most mammals, a bat’s knees point outward and backward. This orientation allows them to hang head-down and control the wing shape during flight, but it prevents a typical forward-striding gait. Most species are thus forced to use their hind limbs only for clinging or a poor crawl.
The Mechanics of Terrestrial Locomotion
The few species that walk well overcome these anatomical limitations using the quadrupedal push-off. This gait repurposes the powerful musculature and structure of the forelimbs—the strongest part of the body due to their role in flight—for terrestrial propulsion. The bat uses the wrist and the modified thumb, which ends in a strong claw, as the primary point of contact and force generation.
When walking, these specialized bats use a symmetrical lateral-sequence gait, a common pattern among four-legged animals. The power comes predominantly from the forelimbs, allowing the bat to scramble or shuffle forward. At higher speeds, the common vampire bat switches to an asymmetrical bounding gait powered uniquely by its forelimbs, resembling running push-ups, rather than the hindlimb-driven bound of most terrestrial mammals.
To facilitate this movement, the wings of these terrestrial specialists are often stiffer and thicker, and can be folded neatly out of the way to prevent damage. The modified thumbs and wrists act as powerful levers, initiating the movement and allowing for surprisingly quick bursts of speed. This unusual locomotion is an evolutionary solution to moving on the ground without sacrificing the ability to fly.
Why Specific Bat Species Walk
The evolution of terrestrial locomotion is directly tied to the ecological need to access food sources unavailable to purely flying bats. The common vampire bat (Desmodus rotundus) is a striking example. Its diet requires it to feed on the blood of sleeping animals, such as livestock. Since flying directly onto a large host risks alerting them, the bat must land nearby and stealthily approach on foot.
This necessity led the vampire bat to evolve into an exceptionally agile runner. It is capable of short bursts of speed up to 2.5 miles per hour using its forelimb-driven bounding gait. This speed is also a matter of survival, providing a rapid escape option if the host animal moves or attempts to dislodge the feeder.
Another notable example is the New Zealand lesser short-tailed bat (Mystacina tuberculata), one of the most terrestrial bats in the world. This bat spends a significant portion of its time foraging on the forest floor, using robust limbs to scurry along the ground, up trees, and through leaf litter. This behavior evolved because New Zealand historically lacked native terrestrial predators, making ground foraging safe and energetically efficient. The bat’s omnivorous diet includes insects, fruit, nectar, and pollen. Studies show they spend approximately 30% of their foraging time hunting insects on the forest floor, where they can dig and burrow for prey that flying bats cannot reach.