The rodent world has long been considered a very quiet world, but recent research has found that the world is full of "singing sounds."
Rats can "sing" like birds – which sounds incredible, but it does.
At the end of 1925, J.L Clark found an unusual mouse in a house in Detroit, USA— it would "sing." He caught the rat and put it in the cage. Rats make melodious lyrical sounds in their cages, like birds singing. Clark gave the rat to a researcher at the University of Michigan, who thought it could "sing." Next, they paired the mice with the lab rats, and their offspring could make a vague "beep" sound, but none of them had the melodious tone of their father's melody. These observations were recorded in a 1932 scientific paper, but over time, these papers were all but forgotten.
Recently, Martina, a biologist at the University of North Carolina, once again studied the mystery of rats "singing." After mastering how to listen to "rat songs", she heard something new.
To catch the rat's "song," Martina and her students did a lot of preparatory work. At night, they wear hard hats and carry luggage, laptops, scales, laptops and recording equipment to the pine forest. They connected six long cables to the speakers and placed them where they thought the rats could "sing," forming a surveillance net. The forest they chose was not very large and not too pristine. It is surrounded by corn, tobacco and cotton. But for them, it was perfect. Because they wanted to listen to the solo of the rats, not the symphony of the animals, and the pine forest was very quiet, and there were no singing creatures like insects on the ground. In order not to sound the alarm for the squirrels, they carefully crossed the wood lying on the ground, came to the torch pine, and turned on the loudspeaker.
At the age of 19, Martina worked as an intern, specializing in bat behavior. Because she was fascinated by the research, she often came outside in the middle of the night and stayed here all night. She is now a behavioral biologist and an expert in animal voice communication. So far, she has worked thousands of hours in the forest, day and night. The snoring of bats, the squeaks of the textile lady, and the "screaming, squeaking" of frogs could not escape her keen ears, which she could - recognize. She gradually became an expert in voice recognition. Of course, occasionally she would encounter voices that she couldn't recognize.
Martina, who has been conducting a study in Monterrey County, North Carolina, since 1996, wanted to figure out if two local rats would call out to each other and make a chirping sound. One night, she thought she heard the "song" of rats, and their sounds were just within the edge of her hearing, just as a seafarer could vaguely perceive land far beyond the horizon.
In 2014, Martina borrowed a manual recorder that recorded ultrasonic scattering and brought it to the North Carolina research field. As part of her research into animal behavior, she caught many mice, labeled them on their ears, and then let them go. Not only could she remember the names of many rats, but she also knew where they lived. She put the tape recorder where the rats often went in and waited patiently.
After waiting for a long night, the researchers brought the recorder back to the lab. They listen to diffuse recordings through headphones, and slow recordings can reduce the audio. If there are new discoveries, they will use a computer to convert the recordings into a sound spectrum, with an audio curve with high and low variations. As a result, they heard unusual sounds.
It was a very high frequency scream, and they used a computer to analyze it, and the result was a new curve. It was a four-tone song, and it was made by a rat. It sounds a bit like a whale's courtship song, with a melancholy tone and a noticeable change in height.
Now, Martina has translated ultrasounds of rats collected from North Carolina and is translating the sounds of rats in the northeastern United States. Her research shows that some songs can only be sent by men and some songs can only be sent by women; Even if they are two close relatives, their singing voices may be very different, just like the robin and the roaring song, which are very different. These differences may help mice identify each other.
Martina also found that certain types of mouse songs become more complex as we age. Mouse songs can be congenital. In experimental mice, rats that sang different songs by rats still maintained their own "singing" style. Martina and her students have now spotted the vocals of four voles, and she suspects there are many other types of rats that can sing. The rodent world has long been considered a very quiet world, and Martina's research proves that the world is full of "singing sounds." With "singing sounds," rats can communicate with each other over short distances, but at the moment we know very little about the meaning of their "singing."
Martina's discovery reminds us that each species has its own unique way of perceiving the world. Bacteria call each other through chemical elements. Mosquitoes can detect the carbon dioxide we exhale. Ants can see polarized light. Turtles can use earth's magnetic field to navigate. Birds can see UV markings on flowers. Snakes can track cigarettes or rabbits. Generates a small amount of heat. Due to the limitations of human perception, we know very little about the different ways in which organisms perceive the world.
After the discovery of Martina, Japanese scientists also confirmed the existence of "singing" mice through experiments. Japanese scientists recently modified a group of "singing" rats. In the experiment, they bypassed several generations of transgenic mice and then examined the newborn mice one by one until they found a mouse that could "sing" like a bird. At present, the laboratory has more than 100 rats that can only "sing".
Previously, some scientists found that birds used a variety of different sound elements, combining them into sound modules, similar to words in human language, according to the rules of language, and then further stringing sound modules into "songs." Some biologists point out that mice are better suited to study this area than birds because they belong to mammals and the brain structure of mice is closer to that of humans. Scientists have found that the average mouse usually makes a "squeak, squeak" sound only when stressed. They looked at how singing mice affected normal mice in the same group, i.e., whether they had a social impact. It turns out that mutant mice are louder when they are placed in a new environment, or when male and female mice are together. Scientists believe that their voices may stem from emotional expression or physiological responses.