Water striders learn from experience how to safely jump off the surface of the water

You probably don’t find it surprising that humans – dogs or cats – can adapt their behavior based on experience. For example, we all move slower after slipping and falling on the ice when we learn to ice skate. A new study shows water striders can do this too.

Water screechers were known to leap up from the surface of the water without breaking it. But how can they do it? How do they know when the water surface would be broken? A multidisciplinary team of scientists from Korea, the United States and Poland found that water striders regulate their jumping behavior by modifying their leg movements based on experience gained during frequent jumps, and that these changes are dependent on experience. the body weight of the animal.

Korean and Polish biologists led by Sang-im Lee (Laboratory of Integrative Animal Ecology, DGIST, Korea) and Piotr Jablonski (Laboratory of Behavioral Ecology and Evolution, Seoul National University and Museum and Institute of Zoology, Polish Academy of Sciences) collaborated with US biologists led by Hangkyo Lim (University of Notre Dame of Maryland) and engineers led by Ho-Young Kim (National University of Seoul) and provided experimental evidence, at least for women walking on water.

Scientists used high-speed video to measure the jumping behavior of males and females of a common Korean water strider species, Gerris latiabdominis. They compared experimentally weighted individuals (heavy individuals) with control individuals (light individuals). Half of the heavy individuals and half of the light ones were prompted to jump every day for three days by frequently hitting them gently for several hours a day, while the other half did not experience frequent jumping during this period. Then the scientists measured their jumping behavior at the start of the experiment and after those three days, and found that heavy females (the ones with the added extra weight) changed their jumping behavior differently than females. without extra weight.

Additionally, the light and heavy body adjustments were only detectable for people who experienced frequent jumps. “We observed adjustments in the speed of the leg movements and the speed of the jump, the end result of the jump,” says Minjung Baek, the first author of the study. Females who had a lighter body weight during the three days of frequent jumping moved their middle legs more slowly than those who were not prompted to jump frequently. On the other hand, females who have a heavier body weight during frequent jumps move their legs faster, as if they “know” that to produce a quick jump they have to “work harder” due to the added weight. But they made these adjustments “carefully” so that the surface tension of the water was not interrupted. Males did not show such a stark difference in the adaptations of their jumping behavior to their body weight.

A question arises: why do we see this difference between males and females? “In water striders, including this species, mating males can ride over females for hours or even days, which means that during mating a female has to support the weight of the mating male in addition to her own. body weight on the surface of the water, “says Dr. Piotr Jablonski, who has previously studied the mating behavior of water striders. “Males do not experience such repeated temporary increases in perceived body weight and therefore do not need the ability to use their experience to regulate their jumping behavior,” adds Dr. Sang-im Lee, who seeks ecological explanations for biological phenomena by integrating biology, physics and engineering.

This interesting result shows how the plastic responses of animals can evolve according to environmental conditions; in this case the optimal behavioral adaptations were made through personal experience. There are many examples of animals, including insects, adapting their behavior to changing environmental conditions through developmental or behavioral plasticity, but this study clearly shows that they can do this through personal experience, just as we do.