When I think about evolution, the most common phrase that comes to mind is “survival of the fittest.” We usually think of this concept as static: one species evolves in such a way that it manages to avoid its predator and not get eaten, allowing it to survive and reproduce – and that’s it. It’s easy to think that evolution ends here, and that if you came back years later the situation would remain unchanged. Unfortunately, that makes evolution seem much more straightforward than it actually is. All species are constantly evolving to give themselves a survival edge, not just the one species in whichever example is used. That means that the predator is evolving at the same time as its prey. This constant race to come out ahead in the battle for survival is called an “evolutionary arms race.”
Here’s an awesome example of the dynamic process of evolution, involving bats (predator) and moths (prey). As you may or may not have known, bats are essentially blind, and hunt by sound instead. They squeak constantly while in flight, and then use to the reverberation of their squeaks to construct a sonar image of things in their path. Each squeak bounces off the objects ahead of the bat and returns to their ears. They use the information from the returning sounds to “see” their surroundings, including the location of their prey (lots and lots of insects) – this is called echolocation. Humans use sonar to create images, too. The bottom of the ocean was mapped using sonar; a boat emits sound waves downward, and then the time for the sound wave to reach the bottom and bounce back up to the ship is recorded to calculate depth of the ocean floor. It’s the same for bats, only they do this habitually, without needing fancy machines and computers.
Sonar is a pretty powerful tool for bats to possess. But apparently there are several types of moth that have found a way to combat this. Some moths have evolved to be able to hear the bats’ echolocation calls, allowing them to evade the bats. In turn, some bats have evolved to use a quieter mode of echolocation, allowing them to take the moths by surprise. Whenever the bats develop a new method for hunting more effectively, the moths respond by developing an ever better method for combatting that advance. They’re locked in a constant battle to one-up one another. Since being able to hear the bats coming isn’t always enough, some moths have gone one step further: they can actually jam bats’ sonar by emitting ultrasound bursts that interfere with the bats’ echolocation. That in and of itself is really neat – a small moth figured out how to emit a sound that blocks bats’ echolocation tools. The real question, however, is what will the bats come up with next to bypass the signal jammer? Because if we know one thing about evolution, it’s that it is always happening, and you either change with the times or perish, and there’s no doubt some bats are already cooking up a response.