托福口语 Task 4

Today we're going to discuss a fascinating concept in animal behavior called 'sensory exploitation.' This idea suggests that certain traits in animals evolve because they exploit pre-existing sensory biases in the opposite sex, rather than because they signal fitness or quality. Let me give you two examples. First, consider the swordtail fish. Females of a closely related species without swords naturally prefer males with longer tails, even though they've never seen a sword. This bias likely existed before the sword evolved. When a sword appeared in one species, males with swords suddenly became more attractive, so the trait spread. Second, think about the tungara frog. Females are innately drawn to a specific low-frequency 'chuck' sound, which is found in many frog species. In tungara frogs, males added an extra 'chuck' to their calls. This extra sound exploits the females' existing preference for chucks, making these males more successful in mating, even though the extra chuck doesn't indicate better genes. So, sensory exploitation shows how traits can arise not from adaptive signaling but from pre-existing biases in the receiver.