The rodent world has long been considered a very quiet world, but the latest research has found that the world is actually full of "songs".
Rats can "sing" like birds – it sounds unbelievable, but it's true.
In late 1925, J.L. Clarke found an unusual mouse in a house in Detroit, USA—it would "sing." He caught the rat and put it in a cage. The rats emit a melodious lyrical tone in their cages, like birds "singing." Clark gave the rat to researchers at the University of Michigan, who believed that the rat could indeed "sing." Next, they mated the rat with a lab rat, and as a result, their offspring produced a vague "chirping" sound, but none of them inherited their father's melodic melodious tone. These observations were all recorded in scientific papers from 1932, 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 the "rat version of the song," she heard something entirely new.
To catch the rats' "songs," Martina and her students did a lot of preparatory work. At night, they wore hard hats and brought carry-on luggage, notebooks, scales, laptop computers and recording equipment to a pine forest. They connected six long cables to the megaphone and put it into a place where they thought the rats might be chanting, forming a monitoring net. The forest they chose was not very large or pristine, and it was surrounded by corn, tobacco, and cotton fields. But for them, it's perfect enough. Because they want to hear the solo of rats, not the symphony of animals, and this pine forest is very quiet, and there are no insects or other singing creatures on the ground. In order not to alarm the singing rats, they carefully stepped over the logs lying on the ground, came to a torch pine, and connected the megaphone.
Martina worked as a trainee physician at the age of 19, specializing in bat behavior. Obsessed with the study, she often came outside in the middle of the night and stayed overnight. She is now a behavioral biologist and an expert in animal voice communication. To date, she has stayed up late in the forest to work thousands of hours. The click of the bat, the scraping of the weaver lady, and the "croaking, croaking" of the frog could not escape her keen ears, and she could recognize it. She gradually became a voice identification expert. Occasionally, of course, she would encounter voices she couldn't identify.
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 2004, Martina borrowed a hand-operated tape recorder that could record ultrasonic scattering, which she brought to her research field in North Carolina. As part of her ethological research, she captured many mice, marked their ears, and then released them. Not only could she remember the names of many rats, but she also knew where they lived. She placed the tape recorder where the rats often came and went, and waited patiently.
After waiting for one long night after another, the researchers brought the tape recorder back to the lab. They listen to slow-play recordings through headphones, which can reduce the sound frequency. If there are new discoveries, they use computers to convert the recordings into a sound spectrum, a kind of sound frequency graph with high and low variations. As a result they heard unusual voices.
It was a high-frequency scream, and they analyzed it with a computer and saw a whole new graph. It's a four-tone song, and it's from a mouse. The sound sounds a bit like a whale's courtship song, with a melancholy tone with a noticeable high and low variation.
Now, Martina has translated the ultrasound sounds of rats obtained from North Carolina and is translating the sounds of rats in the northeast of the United States. Her findings suggest that some songs can only be pronounced by male rats, and some songs can only be pronounced by female rats; Even for two close relatives, their singing can vary greatly, just as the songs of robins and wrens can vary considerably. These differences may help the mice identify each other.
Martina also found that the singing of certain species of rats became more complex as they age. Mouse singing may be congenital, and in laboratory rats, mice raised by mice that sing different songs still maintain their own "singing" style. Martina and her students had now figured out how four wild rats sounded, and she suspected that many other types of rats could sing. The rodent world has long been considered a very quiet world, and Martina's research proves that the world is full of "songs" . Through "singing", rats can communicate with each other over short distances, but at present we do not know much about the meaning of their "song".
Martina's discovery has led us to re-recognize 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 the Earth's magnetic field to navigate, birds can see ultraviolet markings on flowers, and snakes can track traces of heat sources emitted by a cigarette or a rabbit. Due to the limitations of our own human perception, we still know very little about the different ways in which living things perceive the world.
Following Martina's discovery, Japanese scientists have also used experimental methods to confirm the existence of "singing" mice. Japanese scientists recently engineered a batch of "singing" rats. In the experiment, they crossed many generations of transgenic mice and then examined the newborn mice one by one until they found mice that could "sing" like birds. At present, the laboratory has more than 100 rats that can only "sing". Previously, some scientists have found that birds use a variety of different sound elements, according to a certain language rule, combine them into sound modules, similar to words in human language, and then further string sound modules into "songs". Now, biologists have pointed out that mice are more suitable for this kind of research than birds because they belong to the same mammals as humans, and the brain structure of mice is closer to that of humans. Scientists have found that ordinary rats usually only make "squeak, squeak" sounds when there is pressure. They looked at how singing mice affected ordinary rats in the same group, i.e., whether they could have a social impact. It was found that the mutant rats were more vocal when they were put into a new environment, or when the male and female mice were together. Scientists believe that their calls may be due to an expression of emotion or a physiological response.
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