Y: Don, animals can do some pretty strange things when they're trying to attract a mate. Two species of birds, the western grebe and Clark's grebe actually run on the surface of water. The behavior is called 'rushing'.
D: Yaël, as surprising as it sounds, there are actually many kinds of animals that can run or walk on water. Most of them are insects and spiders that are so lightweight that they stick to the water's surface, but a few are heavier. The basilisk lizard runs on water to escape from danger. It uses specially adapted feet and a unique running style to keep from sinking. What's special about the grebes?
Y: These birds weigh between one and a half and four pounds, which makes them much heavier than any other animals that run on water. In 2015, a team of American scientists published the first ever study of how they do it. They made high speed videos to study the movements of the grebes' legs and feet during 'rushing'.
D: What did they find out?
Y: The grebes' leg movements are extremely fast. They take as many as ten strides per second, which is faster than any other bird ever studied. When their broad, lobed feet slap the water's surface, this alone generates about half the force needed to counteract their weight.
D: But don't those broad feet generate lots of drag when the birds lift them back out of the water?
Y: No, the scientists found that they lift their feet back out of the water to the side, with flattened foot bones reducing downward drag.
D: All this must really impress their mate.