The basilisk lizard, often called the “Jesus Christ lizard,” is native to Central and South American rainforests. This nickname comes from its remarkable ability to sprint across the surface of water. This unique locomotion allows the basilisk to escape predators. The intricate design of its feet and the precise mechanics of its movement enable this act.
Unique Anatomy of Basilisk Feet
The basilisk lizard’s ability to traverse water is largely attributed to the distinctive structure of its hind feet. These feet are notably large, featuring long, slender toes. Along the sides of the third, fourth, and fifth toes are specialized fringes or flaps of skin. These scaly extensions are typically compressed against the toes when the lizard moves on land.
Upon encountering water, these fringes unfurl, significantly increasing the surface area of the foot. This expansion creates a wider platform for interaction with the water’s surface. The large feet and deployable fringes play a role in generating the necessary forces to keep the lizard above the water during its rapid sprints.
The Physics of Water Running
The basilisk lizard’s water-running involves a rapid, bipedal gait executed through three distinct phases: the slap, the stroke, and the recovery. This sequence must be performed with incredible speed and precision to counteract gravity and maintain buoyancy. Basilisks can take up to 20 steps per second, moving at speeds of about 1.5 to 5 feet per second (around 0.46 to 1.5 meters per second) across the water.
The first phase, the “slap,” involves the lizard forcefully striking its foot flat against the water’s surface. This initial impact pushes water downwards, generating an upward force. This slap also traps tiny pockets of air beneath the foot, contributing to temporary buoyancy and reducing surface tension.
Following the slap, the “stroke” phase begins as the foot pushes downward and backward into the water. This action causes an air-filled cavity to form around and beneath the foot, which is crucial for the subsequent steps. During the stroke, the foot experiences a lifting force proportional to the amount of water it displaces, propelling the lizard forward and generating the majority of the upward thrust.
The final phase, “recovery,” involves the rapid retraction of the foot from the water. The lizard pulls its foot out from within the air cavity before it can collapse, minimizing drag and allowing for an efficient lift. This swift withdrawal is necessary for the lizard to prepare for the next slap, ensuring continuous propulsion and preventing it from sinking. Juveniles can typically run farther, sometimes 10 to 20 meters, while adults may only cover a few meters before submerging due to their increased weight.
Beyond Water Running: Other Foot Functions
While renowned for their water-running capabilities, basilisk lizard feet serve other functions in their natural habitat. Their robust hind limbs are well-suited for terrestrial locomotion, allowing them to run on land at speeds comparable to their aquatic sprints. They can move on all fours or in an upright, bipedal posture.
The sharp claws on their toes provide excellent grip, making them adept climbers. Basilisks frequently ascend trees to forage for food, often resting on branches overhanging water bodies. When their water-running ability is exhausted or they cannot maintain sufficient speed, basilisk lizards are also capable swimmers, using their strong limbs to navigate underwater. They can even remain submerged for periods, sometimes up to half an hour, to evade aquatic predators.