Why Mice Sing: Sex, and to Protect Habitat

Oct. 6, 2013— -- If a mouse could sing, what would its song say? Most likely either come here sweetie, or get out of my territory.

High in the mountains of Costa Rica two species of mice have attracted the attention of scientists in recent years because, apparently, no one really thought mice could sing.

But biologist Bret Pasch has spent three years capturing, recording and releasing hundreds of mice just to figure out what they have to sing about.

He published his first paper on mice a couple years ago while he was a graduate student at the University of Florida in Gainesville. The paper showed that male mice fill the air with trills so high-pitched that most humans can't even hear them.

Why Would a Mouse Sing?

But if the song is right, and the melody is sweet enough, at least to the ears of a female mouse, the vocalist soon finds himself with a companion.

OK, mice aren't the only animals that sing to win the favors of a beautiful girl. Birds do it. Even whales do it. But is that all there is to the story? No way.

Pasch is now with the University of Texas, and he and his colleagues are out with another paper, published in The American Naturalist. The singing mice of Costa Rica and Panama don't just sing to get the girl. They also sing to warn other mice to stay away.

That might not seem all that important, but to biologists interested in the distribution and diversity of wildlife, how animals decide where to make their homes is an ongoing concern. Generally, those decisions are purely biological.

They live where the living is good. But these tiny mice have complicated the equation. Verbal communications, not just biology, play a role, at least for these mice.

In the lush hills of Central America, the Alston's singing mouse (scotinomys teguina) and the Chiriqui singing mouse (S. xerampelinus) have similar diets, and like living in the forest, so there's plenty of room for conflict. The Alston's is smaller, and more timid, than the Chiriqui, and they both open their mouths about 15 times per second as they sing, Pasch said.

Both species cherish the same territory, but when the Alston's hears the voice of the Chiriqui, it stops singing and flees the area. In other words, it's obeying a vocal command. But are the mice really singing?

Most biologist believe a sound isn't a song unless it comes from an animal with certain physiological features, like those shared among humans and birds, and mice were not thought to have those features.

Most songbirds aren't born singers. They have to learn how to sing. And learning to sing requires an ability to hear someone else, called auditory feedback.

If mice don't have that, they can't learn how to sing. So scientists at the Howard Hughes Medical Institute, Duke University and Tulane University, have spent several years experimenting with mice to see how well equipped they are to sing.

One of several experiments seems to answer that. Male mice from another species of singers thought they were opera stars when they found themselves sharing a room with a female. Or as the scientists put it, the smell of a female "enhanced their subsequent singing responses to the female."

But these guys, sadly, later had surgery that left them deaf. The result: "Striking differences" in their songs. They no longer had that essential "auditory feedback," and their melodies were reduced to "squawks and screams," according to that study, which was also published in PLoS One.

So some mice can learn how to sing, and it serves at least two purposes, attracting a lover and dispatching a competitor. And the story doesn't end there. Pasch said many rodents, including rats and even pet hamsters, produce complex vocalizations.

When we think of singing animals, we usually think of birds. Many species, especially among the 4,600 species of songbirds, produce melodies that can be stunning in their beauty. But, perhaps surprisingly, some of the best singers in the animal world are rarely heard, because they are underwater.

Whether you want to call it music or just noise, vocalizations are immensely important to creatures of the deep. Sound is much more useful than sight in many cases, because light gets absorbed so quickly. The same is true for odors, so smell is not much help.

But sound travels four times faster in water than it does in the atmosphere, and it works as well in the darkness as it does in daylight.

Few sounds, either above or below the water, are a match for the legendary songs of the humpback whale. These songs are haunting and unforgettable -- cries, howls, and moans -- and they play a vital role in the life of the humpback.

Until fairly recently it was thought that the male humpback sings only to attract a mate, but scientists have found that is far from the truth.

In the waters off Alaska, where I live, we have watched the drama of bubble feeding by humpbacks many times, and it's a scene that can never grow old. Underwater microphones pick up a wide variety of sounds as the whales go through carefully orchestrated maneuvers to trap schools of small fish, usually herring.

Some members of the pod produce curtains of bubbles that surround the fish as the bubbles move toward the surface. The fish, apparently unaware that they could simply swim through the bubbles to freedom, remain paralyzed as the whales begin surging from the bottom of the trap to the surface, their huge mouths open, filling with fish as they rise to the top.

That kind of maneuver requires someone in command to issue orders, telling each whale in the drama exactly what to do. You can't understand what they are saying, but you can hear the music with the right equipment, and it is awesome.

The whales will move on later to warmer waters where they will spend the winter, and mate, as the males sing their hearts out in pursuit of a female. Then they will head north again and the males will continue to sing with young pups swimming alongside mom, so close, indeed, that they will frequently touch.

It's no less than a symphony.