With a pink nose, small eyes, wide and flexible ears and a broom-like tail, the pig-tailed mouse, known as the "blind mouse", has an echolocation ability.
Recently, researchers from Kunming Institute of Zoology, Chinese Academy of Sciences came to this conclusion.
The research groups of Shi Peng, Jiang Xuelong and Liu Zhen, the State Key Laboratory of Genetic Resources and Evolution of the Institute, jointly tackled the problem, and confirmed that the species of the genus Rodent has the ability of echolocation by integrating several independent evidences of ethology, anatomy, genomics and gene function experiments.
"In addition to the well-known bats, toothed whales, etc., pigtail rats also have this ability, which is amazing in itself!" On July 5th, one of the researchers, Dr. Liu Qi from Shi Peng’s research group, was interviewed by The Paper (www.thepaper.cn) and introduced that the research on echolocation ability of pigtail rats lasted for about 4 years. This study is expected to make the pig-tailed rat become a new experimental animal to study the neural circuits of sound, hearing and echolocation. He also hopes that the research results can be applied to artificial intelligence in the future, such as improving auto-driving and blind-assisted navigation.
"Are there other mammals that have this ability but have not been discovered?" Liu Qi believes that there is still a lot of room for the research and application of echolocation, and the research on pig-tailed mice is only the beginning.
The experiment lasted for nearly four years, and the researchers stayed up late with the pig-tailed rats.
The nose is pink, the eyes are small, the ears are wide and very flexible, just like bats, they will swing back and forth and collect sounds in different directions. Its tail is very long, shaped like a broom, and there is a pinch of white hair at the end of it.
This is Liu Qi’s research object-pigtail rat, which is also called "blind rat" because of its small eyes. It belongs to the genus pigtail rat of Rodent Echinopodidae.
Liu Qi studied the echolocation ability of pig-tailed rats. Echo location refers to a directional behavior of animals in navigation, foraging and other activities by comparing the information difference between sending sound waves and receiving echoes.
As early as 2017, Liu Qi had already started this research.
At that time, after he did some basic work, the experiment had preliminary research results. He organized the experimental content into an English manuscript and sent it to secience magazine in the form of a short article. Journals have given great affirmation to this research achievement and shown great interest, which has given them great confidence.
"In the later process, we supplemented many experiments according to the requirements of the magazine and constantly enriched and improved the paper." Liu Qi said that on the one hand, it is necessary to obtain accurate experimental evidence from many aspects, on the other hand, the workload of each experiment is very large, including the subsequent papers being revised many times, so the whole project involves a long time, and it is a joint effort of multiple research teams.
Liu Qi introduced that the correspondence authors Shi Peng and Liu Zhen’s research group have been engaged in the research on the convergent evolution and molecular genetic mechanism of echo localization for a long time, and have published many heavyweight research results. Another cooperative team, researcher Jiang Xuelong, who is also the correspondent of the paper, is engaged in the research on the behavioral ecology, phylogeny and classification of pig-tailed rats. This research is the result of joint research by three research groups.
Although there are three top teams in the joint experiment, there are many difficulties in the experiment.
Liu Qi introduced that the first difficulty comes from the research object-the pig-tailed rat. Before the study, they didn’t know much about the living habits of this kind of wild animal, such as what it eats, where it lives, whether it lives in groups, what its nest looks like and its activity time.
Secondly, the wild population of pigtail rat is not large, so it is a big problem to catch it and catch a certain number of live pigtail rats when doing experiments with it.
At the same time, the researchers have no experience in raising pigs. After catching a certain number of pigs, they don’t know how to raise them. They are worried that the artificially created conditions can’t make pigs behave naturally.
However, with the advancement of the experiment, solutions have been found to these difficulties.
What makes Liu Qi feel very interesting is that in the experiment, they found that animals such as pigtail rats are nocturnal. They sleep during the day and are more active at night. Therefore, in the process of behavioral experiments, researchers arrange experiments at night, and sometimes they have to work all night to complete an experiment.
The echolocation function of small-eyed "blind mouse"
Liu Qi said that in the experiment, they recorded the short-term, frequency-modulated and high-frequency sound waves (peak frequency ~98 kHz) regularly emitted by the pig-tailed rats during movement. In dark environment, pigtail rats will emit higher ultrasonic velocity in complex space environment and when avoiding obstacles. All these results show that the ultrasonic waves emitted by pigtail rats play a directional role in sports behavior, that is, echolocation.
Subsequently, the researchers used classic experimental devices and strict experimental design to verify whether the pigtail mouse has the ability of echolocation. Through the behavioral task experiment, it is found that the pigtail rats will spend more time and send out higher ultrasonic speed to explore the target. They can accurately detect the escape platform and successfully obtain food rewards in complete darkness. When its ears are blocked, the pig-tailed rat can’t receive the echo and can’t detect the target and complete the task; After removing the earplugs, the pig-tailed rat recovered its ability to explore and locate the target. Under the condition of eliminating vision, touch and controlling sense of smell, behavioral experiments confirmed that the pigtail mouse achieved its goal by emitting ultrasonic waves and receiving echoes by hearing.
In addition, the researchers used technical means to present the anatomical structure of the pig-tailed rat, and found that the spatial position of its hyoid bone and tympanic bone contacted and fused, which was consistent with the structure of the echolocation bat that sounded through the throat. This shows that the pig-tailed rat and the echolocation bat with laryngeal vocalization have the same anatomical structure basis in vocalization and auditory structure.
Liu Qi and other researchers also sequenced and assembled the high-quality whole genome of the Chinese pigtail mouse. Through evolutionary genomics analysis, it was found that the echolocation of the pigtail mouse originated independently. In the whole genome, the pig-tailed rat and the known echolocation species (bats and toothed whales) are significantly enriched in auditory genes.
By integrating several independent evidences of ethology, anatomy, genomics and gene function experiments, it is confirmed that the species of the genus Rodentia has the ability of echolocation.
It is expected to be used in artificial intelligence, blind-assisted navigation and other fields.
The echolocation ability of pigtailed rats seems to be inferior to that of ordinary people. However, Liu Qi said that this research may be applied to artificial intelligence in the future, such as improving auto-driving and blind-assisted navigation.
Liu Qi said that from the perspective of science itself, echolocation, as a special behavior of animals, is very rare in the animal kingdom. At present, the echolocation species known by human beings may be limited to a few kinds, such as bats and toothed whales, which are familiar to everyone, and some unfamiliar ones, such as some birds, shrews and hedgehogs.
"In addition to the animals listed above, we have confirmed that there is another kind of mouse, which also has echolocation skills. It is amazing in itself to find food or locate targets by hearing and ultrasound!" Liu Qi said that in addition to five groups of independent origin, such as bats, toothed whales and giant whales, the research team found a sixth group with this ability.
In addition, because the pig-tailed rat is a rodent, its genetic relationship and size are close to those of model animal mice, and its breeding is easy to operate, it is expected to become a new experimental animal to study the neural circuits of sound, hearing and echolocation.
Liu Qi said that human beings have developed many bionic products based on the long-term research on echolocation species such as bats. For example, bats will send out ultrasonic waves to detect targets, track moving prey, or avoid obstacles in time. The invented guide rod is convenient for the blind to move.
He admits that there is still a lot of room for the research and application of echolocation, and the research on bats, pigtails and other animals and their echolocation will have more influence on human life in the future.
After discovering that pigtail rats have echolocation ability, Liu Qi and his research team have been thinking about whether there are other nearly 6,000 kinds of mammals in nature that have this ability but have not been discovered. They hope that through the efforts of the team, they can find more such magical animals.
"This requires the unremitting efforts of many researchers, and it may even be a very long exploration process." Liu Qi said that the discovery of pig-tailed rat and its echolocation is only the beginning. They hope to stick to this research and expect that it can be used in artificial intelligence in the future, such as improving auto-driving and blind-assisted navigation.
(This article is from The Paper, please download the "The Paper" APP for more original information)
