Thursday, March 23, 2017
How "Jesus Lizards" Walk on Water? - BIODIVERSITY
The lizards range in size from less than 0.01 ounces (2 grams) upon hatching to more than 7 ounces (200 grams) as adults. Throughout their size range, they can run across water on their hind limbs at about 5 feet (1.5 meters) a second for a distance of approximately 15 feet (4.5 meters) before they sink to all fours and swim. The lizard is often called the Jesus Christ lizard in Central America because of its seeming ability to walk on water.
The stride is divided into three phases: the slap, the stroke, and the recovery. During the slap the foot moves primarily vertically downward. During the stroke it moves primarily backward. And during the recovery the foot moves up and out of the water, returning to the start position of the next step.
The lizards generate force for support during the slap phase, in which the lizards' foot plunges straight down, pushing water down and away from the foot while creating a pocket of air surrounding the foot.
The support force generated by the slap is sufficient to keep the lizards' bodies above the water's surface during the stroke phase in which they propel themselves forward by kicking their leg back through the water.
To stay upright, the lizards also create forces off to the sides called lateral reaction forces.