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Listen to part of a lecture in a biology class. The professor is discussing animal communication. Professor: Today we're going to talk about a fascinating aspect of animal behavior: communication. Now, many of you might think communication is just about sound, like birds singing or dogs barking. But in fact, animals use a variety of signals, including visual, chemical, and even electrical signals. Let's focus on chemical signals, specifically pheromones. Pheromones are chemicals released by an animal that affect the behavior or physiology of another animal of the same species. For example, ants use pheromones to mark trails to food sources. When an ant finds food, it leaves a chemical trail, and other ants follow that trail. This is a very efficient way to communicate. However, pheromones are not just for social insects. Many mammals, including rodents, use pheromones to signal reproductive status. For instance, a female mouse in heat releases pheromones that attract males from a distance. Interestingly, pheromones can also convey alarm. When a fish is injured, it releases a chemical that causes nearby fish to flee. So, as you can see, chemical communication is widespread and serves many functions.