Frogs primarily eat insects for sustenance. However, biologists once encountered a strange phenomenon during an experiment: they placed a pile of dead flies next to the captive frogs, yet the frogs ended up starving to death.
Later, a scientist studying penguins reported a similar observation: in his eighteen years of breeding penguins, he never saw a penguin picking up dead fish from the ground to eat. Instead, they either caught live fish in the water or were hand-fed one by one.
Subsequently, similar occurrences were discovered in many other animals, including swallows and bats. This piqued the interest of scientists: why do these animals exclusively eat live prey? Don’t they like eating dead animals?…
After numerous studies and observations by scientists, the “mystery” was finally unveiled. It turns out that these animals only eat live prey not because they dislike eating dead things. If you don’t believe it, you can conduct an experiment yourself: put a colored rope in a fish tank. When the rope sinks to the bottom, you will see the fish swim over to eat it (of course, the rope is not food, and the fish will eventually spit it out); however, if you fix the colored rope in the center of the water, preventing it from sinking to the bottom, or simply let the rope sink to the bottom of the tank, the fish will not swim over to eat it. If you’re interested, you can continue the experiment: gently stir the water in the fish tank, causing it to swirl slowly… the rope in the water will also sink and float with the water’s movement. Suddenly, the fish will swallow the rope again.
Now you understand that fish don’t dislike eating dead things; it’s just that they won’t eat things that remain motionless!
But what’s the reason behind this? Scientists believe that this characteristic is related to their eye structure. The crystalline lens of animals like frogs and fish is a transparent sphere that protrudes significantly. Moreover, they lack ciliary muscles to adjust their vision, so their eyesight is limited to close distances. They cannot clearly see objects that are far away; they can only vaguely perceive the movement of objects. Since dead flies neither crawl nor fly and remain quietly piled up, how could a frog see them? If there are no other live insects available for captive frogs, they will undoubtedly starve to death!