Is gliding truly the pinnacle of arboreal locomotion, or have we overlooked the nuanced mastery of climbing in flying squirrels?

Two Modes, One Animal

Flying squirrels are celebrated for their gliding prowess, yet their climbing abilities are equally remarkable. This duality raises questions about the evolutionary pressures shaping their locomotion.

Static gripping defies gravity

Climbing demands exceptional grip strength and limb coordination. Flying squirrels exhibit specialized adaptations, such as elongated limbs and sharp claws, enabling them to navigate vertical terrains with agility. Their muscular forelimbs and flexible ankle joints provide stability and control during ascent.

Membrane-driven gliding slices through air

Gliding, facilitated by the patagium—a skin membrane extending from wrist to ankle—allows flying squirrels to traverse distances between trees efficiently. This adaptation minimizes energy expenditure compared to climbing down and up separate trees. However, gliding requires precise control over body posture and tail positioning to manage trajectory and landing.

Southern flying squirrel under the microscope

Examining the southern flying squirrel (Glaucomys volans) reveals intricate biomechanical features supporting both climbing and gliding.

Elastic cartilage in the wrist acts like a spring

The wrist joint contains elastic cartilage that stores and releases energy, aiding in the rapid extension of the patagium during takeoff. This mechanism enhances the efficiency of transitioning from climbing to gliding.

Tail ruddering tweaks midflight trajectory

The tail functions as a rudder, allowing mid-air adjustments to direction and stability. By altering tail position, flying squirrels can navigate obstacles and target precise landing spots.

What about colugos, sugar gliders, and tree frogs?

Comparing flying squirrels to other arboreal gliders and climbers highlights diverse evolutionary solutions to similar ecological challenges.

Energy costs tell a different story

Colugos possess extensive patagia, enabling longer glides but at the cost of reduced climbing agility. Sugar gliders, while adept at both climbing and gliding, lack the specialized wrist cartilage found in flying squirrels, potentially affecting their takeoff efficiency. Tree frogs rely solely on climbing, utilizing adhesive toe pads without any gliding adaptations.

Engineering lessons and ecological stakes

Understanding the biomechanics of flying squirrels offers insights into bio-inspired engineering and conservation strategies.

Forest fragmentation bends the biomechanics

Habitat fragmentation disrupts the availability of suitable gliding and climbing substrates, forcing flying squirrels to adapt their locomotion strategies. This shift may influence their survival and reproductive success, underscoring the importance of preserving continuous forest habitats.

In dissecting the biomechanics of flying squirrels, we uncover a delicate balance between climbing and gliding adaptations, each tailored to specific environmental demands. This duality challenges the notion that gliding is the superior mode of arboreal locomotion, revealing a more complex interplay of evolutionary traits.