Bats are widely recognized for their mastery of the skies, being the only mammals capable of true and sustained flight. Their aerial agility allows them to navigate diverse environments, from dense forests to open landscapes. However, a lesser-known aspect of their biology reveals that some bat species also exhibit remarkable proficiency in terrestrial locomotion, including the ability to run on the ground. This surprising capability showcases a fascinating dimension of bat adaptations beyond their primary mode of transport.
The Surprising Reality of Bat Locomotion
While most bat species are adapted for flight and appear clumsy on solid ground, certain bats are surprisingly adept at terrestrial movement. Their bodies are primarily engineered for flight, making extensive ground travel challenging for many species. Despite this, some bats have evolved specialized gaits enabling them to walk, crawl, and even sprint across surfaces. This terrestrial proficiency is a specialized behavior, not universal among all bats.
This ground movement differs from the typical shuffling of most bats, which struggle to move effectively without flight. Efficient ground movement is a specific adaptation in particular lineages, allowing them to exploit resources or navigate situations where flight is impractical. It highlights the diversity within the Chiroptera order and the varied evolutionary paths bats have taken.
The Ecological Drivers of Ground Movement
Certain bat species engage in ground movement due to ecological pressures and opportunities. Foraging is a primary driver, as some bats hunt ground-dwelling prey like insects, scorpions, or small vertebrates. The common vampire bat, for instance, lands near its sleeping prey and then walks or runs to approach silently before feeding on blood. This stealthy ground approach allows them to access food difficult to obtain directly from the air.
Ground locomotion also serves as a means of escaping predators, especially when flight is not immediately possible or quick evasion is needed. While many bats are vulnerable on the ground, running species can quickly retreat from danger. Additionally, navigating confined spaces like caves, rock crevices, or dense undergrowth necessitates ground movement where flight is not feasible. Walking or crawling provides access to otherwise inaccessible roosting or foraging areas.
Unique Adaptations for Terrestrial Travel
The capacity for effective ground locomotion in certain bats stems from anatomical and physiological adaptations. A notable feature is the rotation of their hind limbs, allowing their knees to point backward or outward, unlike most mammals. This orientation provides a more stable and powerful pushing motion for terrestrial movement, enabling efficient forward propulsion. This contrasts with the typical forward-bending knees seen in humans and many other mammals.
The structure of their wing claws and thumbs plays a role in their ground agility. The thumb, equipped with a claw, aids in grasping surfaces and contributes to propulsion, while other wing digits can also be used for support. Vampire bats employ a “front-wheel drive” mechanism, using their powerful forelimbs to generate force and propel themselves in a bounding gait. This forelimb-driven propulsion sets their running apart from other terrestrial mammals.
Bat Species Known for Running
Among diverse bats, two species stand out for their running abilities: the common vampire bat and the New Zealand lesser short-tailed bat. The common vampire bat (Desmodus rotundus) is known for its terrestrial agility, capable of walking, crawling, and sprinting across the ground. These bats can reach speeds of up to 2.5 miles per hour (approximately 4 kilometers per hour) on land, using a bounding gait to quickly approach prey. Their ability to move silently on the ground is crucial for feeding on sleeping livestock.
The New Zealand lesser short-tailed bat (Mystacina tuberculata) is another example, recognized as one of the most terrestrial bat species. This omnivorous bat spends much of its time foraging on the forest floor, scurrying through leaf litter to find insects, nectar, pollen, and fruit. They use their folded wings as additional limbs for propulsion, showcasing ground movement adapted to an environment historically lacking terrestrial mammalian predators.