Fast Belly Flop: Researchers reveal cricket frog’s unique skill

Can frogs walk on water? Some species have captivated observers with their ability to jump from side to side from the surface of a pond or soar into the air as if the water were land. One such breed, native to Virginia and North Carolina, is the cricket frog. The way these frogs move underwater could provide insights into future tools such as robotics and watercraft.

Jake Socha, the Samuel Herrick Professor of Mechanical Engineering, is leading a team of researchers studying the cricket frog’s unique ability to “skitter,” another name for jumping multiple times in a row. The research team’s findings were published in the Journal of Experimental Biology, with graduate researcher Talia Weiss serving as lead author.

“Skitterling is actually not a well-defined word for this behavior; a naturalist used it in 1949 to describe the ‘jumping on water’ behavior of frogs. Since then, it has been used for this type of locomotion in all the literature below,” Weiss said. “Part of this research is not only to study this behavior in cricket frogs, but also to try to come up with a more precise and scientific definition of ‘skittering’.”

how do they do it? In their research, Soča’s team members found that while there is a general belief that frogs can cross water without sinking, doing so may still require highly specialized anatomy. . What does this frog have that other frogs don’t have?

“Our lab studies a wide variety of animals, and many exhibit interesting behaviors when navigating their environments,” Professor Sorcha said. “Even though this humble cricket frog lives nearby, it still amazes us with its abilities and fuels our curiosity to understand the world in which it lives.”

Fast video for fast frogs

The cricket frog is one of the smallest frogs in North America and can easily fit on the thumb of the average adult hand. To observe the cricket frog’s movements, team members used high-speed videography. They recorded how the frogs leaped both on land and in the water, observing the movements of their legs as they moved through both.

The researchers discovered that every time the frog jumps, it actually sinks. “Skitterling” depicts a frog jumping freely with just its feet stuck in the water, but the recording showed a different story. Sorcha, Weiss, and their teammates watched as the frog’s entire body was submerged every time it jumped down.

The movement was not like a frog jumping or dancing freely on the water, but more like a flopping motion. Their movement might be more appropriately called “dolphinization,” after the movement used by porpoises and dolphins, which involves launching themselves out of the water and into the air.

launch from water

The reason cricket frogs have appeared to be dancing on water is primarily because they move quickly.

To record this ultra-fast movement, the researchers used a 20-gallon glass aquarium and released frogs into it. A high-speed camera that shoots at up to 500 frames per second was pointed at the side of the glass aquarium to capture the vertical movement of the water surface. As the frogs jumped around, the team found a way to escape.

The footage was then slowed down to a fraction of its original speed. When team members saw the footage, they made the surprising observation that the frog had indeed sunk.

“It’s interesting how easily we can be fooled by the fast movements of animals,” Sorcha says. “Here we are fooled by a frog that looks like a stepping stone, but is actually jumping or dunking many times in a row. Frogs are good at jumping, but most frogs do not exhibit this porpoise behavior. Is there a special reason why frogs jump, or is it just their small size?”

By observing in slow motion, team members were able to observe the frog’s movements as it retracted and extended its limbs. They also noticed that the angle of the body relative to the water surface was a factor that gave it the ability to balance underwater. They subdivided each jump cycle into:

Take-off from a submerged position Airborne or stay in the air after a jump Re-entry, returning to the water Recovery, resetting for the next jump

In just over a second, the frog takes off completely submerged, pushing its legs underwater to push its body above the surface. The hind legs remained extended as it moved through the air, while the front legs extended forward as they were pressed against the body. The extended front legs are the first to hit the water upon re-entry, and the hind legs remain extended as they sink. As it sinks, its hind legs retract and bend into a jumping position. Another jump is performed and this behavior is repeated.

It’s basically an abdominal flop.

The researchers observed that the frog made eight jumps in a row, completing each jump within a second.

Understanding skittering is an important discovery for the field of biology, but it holds other keys as well. This discovery provides a new physical basis for the future of bio-inspired robotics. It could be applied to water quality testing systems that need to be quickly deployed, as well as amphibious drones that measure water depth. These futuristic devices are inspired by nature and can use tried-and-tested methods that frogs have used for centuries.