Lizards are a remarkably diverse group of reptiles, found globally with diverse forms and behaviors. Among their many adaptations, their ability to move with impressive speed stands out as a significant factor in their survival. This rapid movement allows them to navigate environments, escape danger, or secure resources. Understanding how they achieve such swiftness reveals intricate details about their biology and the pressures that have shaped their evolution.
How Lizards Run
Lizards primarily move using a quadrupedal gait. Their running involves a characteristic side-to-side undulation of the body and tail. This S-shaped lateral bending of the body is synchronized with their limb movements, increasing stride length and contributing to faster speeds.
Some lizard species exhibit bipedal locomotion, lifting their forelimbs off the ground. This shift is often a mechanical consequence of strong propulsive forces from their hindlimbs during acceleration. The tail plays a balancing role during bipedal running, acting as a counterweight, aiding in stability and control. Undulatory body movements, especially of the waist and tail, contribute to increased stride and faster running.
Physical Features for Speed
Lizards possess specific anatomical and physiological features. Their powerful limb musculature allows for quick acceleration and abrupt changes in direction. The muscles in their hind limbs, particularly, are capable of delivering high instantaneous peak power, up to 952 W kg−1 muscle, which is directly met by the muscle fibers themselves without needing external mechanical amplification.
Specialized foot structures also contribute to their speed and agility on various terrains. Some desert geckos and lizards like Uma and Acanthodactylus have fringes on their toes, which increase surface area and prevent them from sinking into loose sand. Arboreal species such as geckos and anoles feature lamellae with microscopic spatulae on their toe pads, providing adhesion that allows them to cling to vertical surfaces and navigate complex environments. The tail serves multiple functions beyond balance, acting as a counterbalance during rapid movements and as a propulsive aid.
Reasons for Rapid Movement
The ability of lizards to move rapidly serves several ecological and behavioral purposes. A primary reason is to evade predators.
Rapid movement is also important for foraging, enabling lizards to ambush or pursue prey with sudden bursts of speed. Beyond survival, speed is utilized in social behaviors such as territorial displays and courtship rituals. Some lizards also use rapid bursts of movement for thermoregulation, moving swiftly between sun-exposed and shaded areas to maintain their preferred body temperature. Lizards often exhibit an intermittent running pattern, characterized by short bursts of speed followed by pauses, due to the physiological challenge of coordinating breathing with locomotion, as the same muscles are often used for both actions.
Remarkable Running Lizards
Several lizard species are particularly renowned for their impressive running capabilities. The frilled-neck lizard (Chlamydosaurus kingii) can run bipedally, reaching speeds of up to 24 km/h (15 mph). The basilisk lizard (Basiliscus basiliscus), often called the “Jesus Christ lizard,” is famous for its ability to run across the surface of water for short distances, utilizing its large, fringed feet and rapid steps to stay afloat momentarily.
The collared lizard (Crotaphytus collaris) also runs bipedally, reaching speeds of about 26 km/h (16 mph) due to its powerful hind legs and lightweight body. Six-lined racerunners (Cnemidophorus sexlineatus) are known for their long hind legs and burst sprinting ability, achieving speeds of up to 32 km/h (20 mph), fueled by a high metabolism that allows them to cover ground quickly with minimal rest. The Perentie (Varanus giganteus), an Australian monitor lizard, can sprint at speeds of up to 40 km/h (25 mph) thanks to its long, muscular body and remarkable endurance, enabling it to maintain speed over longer distances.