托福口语 Task 4

Today, we're going to talk about a fascinating concept in animal behavior called 'sensory exploitation.' This is when a male animal evolves a trait that exploits a pre-existing sensory bias in the female, making him more attractive for mating. The key point is that the female's preference is not for the trait itself, but for something already in her sensory system. Let me give you two classic examples. First, consider the swordtail fish. Female swordtails naturally prefer males with longer bodies, even without any sword. However, males that evolved a sword-like extension on their tail fin are more successful because females are drawn to the elongated shape—it mimics a larger body. Second, think about the tungara frog. Female frogs are attracted to a certain low-frequency call, which naturally resembles the sound of a large predator approaching. Male tungara frogs add a 'chuck' to their call, which exploits this bias for low-frequency sounds, making them seem larger and more dangerous, thus more attractive. So, in both cases, the trait evolved not because it indicates quality, but because it taps into an existing sensory bias.