The question of whether lizards slither like snakes often leads to confusion, given their superficial similarities. While both reptiles exhibit elongated bodies, most lizards propel themselves differently from the distinctive slithering motion of snakes. This difference arises from their distinct evolutionary paths and anatomical adaptations.
How Most Lizards Move
Most lizard species employ quadrupedal locomotion, utilizing all four limbs. Their typical gait involves a sprawling posture, with legs extending out to the sides and bodies exhibiting a noticeable side-to-side bending motion with each step. This lateral undulation of the trunk works with their limbs; as one diagonal pair of feet moves forward, the body bends in the opposite direction. This coordinated movement increases stride length and generates propulsive force, allowing them to run, climb, and burrow.
Lizards also frequently use their tails for balance, especially when navigating uneven surfaces or climbing. Some species have evolved specialized movements, such as bipedalism, where they run on their two hind legs for short, rapid bursts to escape predators or pursue prey. Other adaptations include gliding, seen in species like the “flying dragon” (genus Draco), and even running across water, as demonstrated by the basilisk lizard.
Understanding Slithering
Slithering, scientifically known as lateral undulation, is the most common form of locomotion for snakes. This movement involves the snake creating a series of S-shaped curves along its body. These curves push against environmental irregularities like rocks, branches, or subtle bumps on the ground to generate forward propulsion. The snake’s flexible spine, composed of numerous vertebrae and ribs, allows for this extensive body bending.
The specialized ventral scales of snakes play a significant role. These broad, overlapping scales are connected to muscles and can be angled to increase friction in one direction while reducing it in others. This directional friction, combined with the rhythmic contraction and relaxation of muscles, enables the snake to glide smoothly forward without limbs. Other snake movements, like concertina, rectilinear, and sidewinding, also rely on their unique anatomy and scale properties to achieve movement in various terrains.
The Case of Legless Lizards
A primary source of confusion arises from legless lizards, which are lizards that have independently lost their limbs over evolutionary time. While they move with undulating, snake-like motions, their locomotion differs from true snakes. Legless lizards often exhibit more rigid body movement than highly flexible snakes. They may use a “simple undulation” where body bends push laterally against surfaces, but these bends might not deform locally around objects as efficiently as a snake’s “lateral undulation.”
Several key features distinguish legless lizards from snakes. Most legless lizards possess external ear openings and movable eyelids, neither found in snakes. Another differentiating characteristic is the tail; legless lizards typically have a very long tail, often accounting for a significant portion of their total body length, whereas snakes have a proportionally shorter tail. Additionally, snakes have a forked tongue used for chemosensation, while most legless lizards have a rounded, un-forked tongue.