Squirrels often fall from trees, leading many to wonder how they survive seemingly unharmed. Squirrels are indeed remarkably resilient to falling, a trait attributed to a combination of physical characteristics and behavioral strategies. While they possess impressive abilities to withstand impacts, their survival is not a matter of immunity to physical forces.
Understanding Terminal Velocity
An object falling through the air accelerates until the force of air resistance balances the force of gravity, at which point it reaches a constant speed known as terminal velocity. Squirrels, being small and lightweight, possess a low terminal velocity compared to larger animals or humans. Their relatively large surface area-to-mass ratio, especially when they spread their limbs, greatly increases air resistance, effectively slowing their descent. This means that whether a squirrel falls from a tall tree or a much greater height, it will eventually reach the ground at roughly the same, survivable speed. Some estimates suggest a squirrel’s terminal velocity is around 20 miles per hour, a speed from which they can often recover without serious injury, making this low impact speed a primary reason for their survival.
Squirrel Anatomy and Physiology
Squirrels possess several biological features that contribute to their remarkable ability to endure falls. Their skeletal structure is notably light and flexible, allowing them to absorb impact forces more effectively than animals with denser, more rigid bones. This flexibility extends to their spine, which can bend and twist to distribute shock upon landing. Their strong muscles, particularly in their limbs, further assist in cushioning the impact. Additionally, their bushy tails, while not acting as parachutes, contribute to air resistance and aid in controlling their movement while airborne, also acting as a counterbalance to maintain stability and adjust trajectory during a fall.
The Art of Landing
When a squirrel finds itself in an uncontrolled descent, it employs specific behaviors to minimize potential injury. They instinctively spread their limbs wide and flatten their bodies, effectively increasing their surface area and maximizing air resistance. This “pancake” posture helps to further slow their fall and distribute the force of impact over a broader area. As they approach the ground, squirrels often orient themselves to land on all fours, using their flexible joints and muscles to absorb the shock. In some instances, they may even roll upon impact to dissipate any remaining energy, which allows them to reduce the severity of the landing.
When Falls Become Dangerous
Despite their remarkable adaptations, squirrels are not impervious to injury from falls, and while well-equipped to handle typical tumbles from trees, certain conditions can still pose significant risks. Landing on particularly hard surfaces like concrete or asphalt, or encountering sharp objects during their descent, can lead to severe injuries or fatalities. Falls from extreme or unprecedented heights, exceeding the limits of their physiological adaptations, could also be dangerous, though their low terminal velocity makes this less common. Additionally, a squirrel that is already injured, unwell, or malnourished may be more susceptible to harm from a fall that a healthy individual would easily survive. While rare, instances of squirrels sustaining injuries like head trauma or fractures from falls have been observed, emphasizing that their resilience has limits under specific, adverse circumstances.