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Narrator: Listen to part of a lecture in a biology class. Professor: Now, let's talk about animal communication. Most people think of sounds, like birds singing or dogs barking, but many species rely heavily on chemical signals called pheromones. For example, ants use pheromones to mark trails to food sources. When an ant finds food, it releases a trail pheromone on its way back to the nest. Other ants follow this chemical trail. Interestingly, the strength of the pheromone signal can indicate the quality of the food. If the food is rich in energy, the ant releases more pheromone, attracting more workers. But here's a twist: some insects, like certain moths, use pheromones for mate attraction. The female moth releases a specific chemical that can travel long distances, and the male moth detects it with his antennae, which are extremely sensitive. In fact, a male moth can detect a single molecule of the pheromone. So, while sound is important, chemical communication is often more subtle and, in some cases, more precise.