Why Do Crickets Chirp?

Instructor: Stephanie Gorski

Steph has a PhD in Entomology and teaches college biology and ecology.

In this lesson, we will learn about different chirps crickets use to communicate, and how the good genes hypothesis predicts that these communications will be truthful. We will also discuss some of the downsides of chirping for crickets.

Communication in Crickets

Crickets use sound much like you do, for communication. What would a cricket want to say to another cricket? How about 'I'm lonely'? Or even 'I think I love you'? What about 'Back off'?

Only male crickets chirp. Female crickets choose how to respond to a male's chirp. There are three basic kinds of male cricket chirps. We can think of them as the 'I'm lonely' chirp, the 'I think I love you' chirp, and the 'Back off!' chirp.

  1. Male crickets use the 'I'm lonely' chirp to attract females. Also called the calling song, this chirp is fairly loud and exhibits a regular pattern. Female crickets are attracted to the song and move towards the source.
  2. The 'I think I love you' chirp is also known as the courtship song. This one is typically a low, soft scraping song. Think of a raspy-voiced male singer singing a romantic song. The courtship song typically occurs after the female has found the male, when the male is attempting to mate with her.
  3. The 'Back off!' chirp may be known as the aggressive song, the rivalry song, or the triumph song. It occurs during or after a fight with another cricket. It tends to be a very loud trilling noise.

Honesty in Cricket Communication

If you're trying to attract a potential mate, you might 'display' by showing off your best qualities. You might try to guess what your love interest wants, and make sure he or she knows that you possess those qualities. Are you a really nice person? Are you strong? Are you smart, talented, or rich? Often, courtship displays in animals, such as a cricket's song, are intended to convey information about the sender's health and quality as a mate.

Maybe at some point in your life you've tried to lie about yourself to impress someone. If you have, you know that it's not that easy. Pretending to be strong or smart is difficult. Pretending to be rich is expensive. By a similar token, animal mating displays are usually honest-- either because the mating displays themselves are difficult, or because faking them isn't worth the effort. So they work because they tend to be honest indicators of good health. We call this the good genes hypothesis.

Similar logic can also be used for fighting displays, such as the cricket's aggressive song. The aggressive song indicates that a cricket is willing and able to continue to fight. If a cricket sings an aggressive song but isn't ready to continue to fight, he's setting himself up for a rough time. So it doesn't really benefit him to lie about it.

Costs of Chirping

There is a dark side to crickets chirping, however. There are plenty of animals out there that would love to eat a cricket, and chirping just allows them to find their meal.

Take, for instance, the parasitoid fly Ormia ochracea. This fly lays her eggs inside live crickets. Her young then use the cricket for a living meal and eat their way out, killing the cricket.

This fly has recently become common on some islands in Hawaii. Researchers have been tracking the evolutionary responses of crickets to the fly since the 1990s.

Though they've only had a few decades-- a blink of an eye to evolution-- crickets on Hawaii seem to have found a solution. The parasitoid flies use cricket chirping as a way to find their victims. So many of the crickets in Hawaii have gone silent.

Does this mean crickets have a hard time finding mates in Hawaii? It does. Scientists have observed that silent males will often find females by finding the few males that still call (charmingly called 'wingmen') and sitting near them. Hopefully for the silent males, they can then intercept a female on her way to a calling male. This may help them overcome their inability to produce the calling song.

But what about the courtship song? Many female crickets won't mate with a male that can't sing a courtship song. Scientists believe that, even before parasitoid flies arrived in Hawaii, Hawaiian female crickets were less choosy than other populations of crickets. This seems to be because Hawaii's original population of crickets was very small, and Hawaiian females that were very choosy may never have gotten to mate at all. So this coincidence means that it was much easier for Hawaiian males to evolve silence as a means to avoid parasitoid flies.

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