Squirrels often survive falls from heights that would severely injure or prove fatal to many other creatures. Their resilience stems from a fascinating interplay of physics and biological adaptations that minimize impact.
Understanding the Physics of Falling
An object falling through air accelerates until air resistance balances gravity, reaching a constant speed known as terminal velocity. For squirrels, their relatively small mass and large surface area contribute to a remarkably low terminal velocity. A typical gray squirrel, weighing around 0.5 kg, has a terminal velocity of approximately 20 to 23 miles per hour (around 9 to 10 meters per second). This is significantly lower than a human’s terminal velocity, which can be around 120 miles per hour.
The large surface area-to-mass ratio means that air resistance acts as a strong braking force on a falling squirrel. This resistance prevents indefinite acceleration, with maximum speed reached within seconds. Consequently, whether a squirrel falls from a tall tree or a much greater height, it will hit the ground at roughly the same, relatively low, speed. This principle explains why squirrels often survive falls catastrophic for larger animals.
Nature’s Design for Squirrel Survival
Beyond physics, squirrels possess biological and anatomical adaptations enhancing impact resilience. Their skeletons are lightweight and highly flexible, allowing them to absorb and distribute the force of landing across their bodies. This flexibility extends to their spine, which can bend and twist, further cushioning the shock of impact. Their bones are also resilient, withstanding forces that might break those of other animals.
When falling, squirrels instinctively splay their limbs, increasing their body’s total surface area and creating a “parachute effect.” This posture maximizes air resistance and further slows their descent. Their bushy tail also plays a crucial role, acting as a rudder for steering and balance during the fall, and contributing to drag to reduce descent speed. Skeletal flexibility, strategic body positioning, and tail utility provide significant evolutionary advantages for survival.
The Moment of Impact
Upon contact, a squirrel’s flexible body, splayed limbs, and maneuverability dissipate landing force. They absorb impact by relaxing limbs and loosening their bodies just before contact, then quickly contracting muscles to regain control. This allows them to distribute the energy of the fall over a larger area and through their joints, minimizing severe injury. Their forelimbs manage a significant portion of landing energy, cushioning impact.
Due to their low terminal velocity, the force of impact is considerably less than for larger animals or humans falling from the same height. While a jolt may occur, their specialized physiology is well-suited to minimize traumatic injuries. They can also adjust their body position mid-air to orient themselves for a more favorable landing, often landing on all four feet.
When a Fall Becomes Fatal
Despite their remarkable resilience, squirrels are not immune to injury or death from falls. Landing on unyielding surfaces like concrete or rocks significantly increases the risk of severe injury or fatality compared to softer surfaces. A direct head impact or landing in an awkward position can also lead to fatal injuries.
Underlying health issues, such as old age or existing injuries, can compromise a squirrel’s natural ability to withstand falls. While low terminal velocity protects them, unusual circumstances or repeated high-impact falls can still be detrimental. Falls from extreme heights, though often survivable, may occasionally result in broken bones or internal trauma.