JOEL SARTORE, NATIONAL GEOGRAPHIC PHOTO ARK
Chinese dwarf rat. Little is known about these mice, and there may be more than four species in their genus. The research team also suspects that there are other animals outside this genus that also have the ability to navigate in the dark.
Nationalgeographic.co.id—Under the cover of darkness in the mountain forests of East Asia, rat–rat Chinese dwarfs emerge from the trees to run on branches and forest floors, scavenging for berries, seeds, and insects. What makes this scene extraordinary is that animal–animal it’s almost completely blind.
So how do they get around? A new study published on June 18, 2021 in the journal Science demonstrate conclusively that they do echo. That is, rat–rat The Chinese pygmy senses their surroundings and navigates by sending out high-frequency squeaks, then listening for echoes bouncing off nearby objects.
Previous research has shown that other tree-climbing relatives in the same genus, rat Vietnamese dwarfs, chances are they can also do echo. But this is the first study to gather evidence and prove beyond any doubt that the ability exists in all four species of the genus Typhlomys, also known as the group. rat fluffy tree.
“Economy across all species of the genus did surprise us,” said Peng Shi, senior author of the study, a researcher at the Kunming Institute of Zoology at the Chinese Academy of Sciences. National Geographic.
There is some evidence that shrews and tenrecs—a diverse group of small mammals endemic to Madagascar—can also perform echo, although almost certainly not as effective bat and cetaceans. Shi says that this ability has likely evolved independently in five different mammalian lineages. Some bird species, for example, including oilbirds and swallows, use the form echo which is simpler.
JOEL SARTORE, NATIONAL GEOGRAPHIC PHOTO ARK
Chinese pygmy rat (Typhlomys cinereus) from private collection.
In 2016, Aleksandra Panyutina, a biologist at the Severtsov Institute of Ecology and Evolution in Moscow, produced evidence that Vietnamese pygmy rats can avoid obstacles in a laboratory in complete darkness. He recorded some of the sounds of the rats, which have a frequency and rhythm similar to those of echolocating bats: very high-pitched and repeated, in some cases, dozens of times per second.
Panyutina worked closely with Ilya Volodin, a biologist at Lomonosov Moscow State University, and other colleagues. Together they learned more about the rats’ vocalizations and studied their eyes. The eyes of the mice were “not only very small, but they also had very few light-receiving cells,” Volodin said.
In a new study published this month, Shi and his colleagues collected four species of pygmy rats from mountains across China. Each species has a body length of several inches and soft grayish-brown fur. In the laboratory, they conducted experiments in complete darkness to test their subjects’ ability to echolocation.
First, the researchers compared the behavior of the pygmy mice in a cluttered room and the same animals in an uncluttered room. They found that the animals in the former setting, compared to the latter condition, significantly increased the frequency and number of ultrasonic calls. Next, they showed that the animals could find their way through small holes in the board housing, but only after emitting a series of squeaks.
The scientists also introduced the mice to the enforced disk and allowed them to explore. Under this platform they placed a narrow path that led to the food prizes. All rats raise their calls and can descend to the street in complete darkness. The researchers also put earplugs in the mice and let them try again. This time, they couldn’t find a way and made fewer ultrasonic vocalizations.
The scientists compared the bone structure of the tree rats to those of bats that did echolocation. They then found surprising similarities in the structure of the pharyngeal region, behind the mouth and nasal cavity, where the sound is produced. Likewise, they found that the tree rat’s stylohyal bone fused with the tympanic bone, near the ear. The only other mammals with this structure are bats.
Alexei V. Abramov / Wikimedia
The Chinese pygmy rat (Typhlomys cinereus) is a species of rodent from the family Platacanthomyidae found in China and Vietnam.
This anatomical similarity suggests homoplasy, a type of convergent evolution, in which similar traits develop in different and unrelated species, said Rebecca Whiley, a researcher and master’s student in the Sensory Biophysics Lab at York University, who was not involved in the paper.
Next, the researchers sequenced the genome rat the Chinese dwarf and compare it to dolphins and two types bat. They found more similarities in hearing-related genes than could be explained randomly. They also found that one important gene related to vision, which helps cells in retinal function, was not functional in all four species rat the tree. This is further proof that animal–animal it can barely see.
Shi and his fellow researchers look forward to continuing to study animal–animal this and maybe even their relatives. Rat–rat little is known, and there may be more than four species in their genus. Shi also suspects there is animal others outside this genus that have also the ability to navigate in the dark.