UCLA scientists report for the first time on the only known frog species that can communicate using purely ultrasonic calls, whose frequencies are too high to be heard by humans. Known as Huia cavitympanum, the frog lives only on the Southeast Asian island of Borneo.
Ultrasounds are high-pitched sounds more than 20 kilohertz (kHz) in frequency, which exceeds the upper limit of sounds detectable by humans and is far higher than the 5 to 8 kHz frequencies most amphibians, reptiles and birds are capable of hearing or producing. Key parts of the ear must be specially adapted to detect ultrasounds.
The frogs can hear sounds up to 38 kilohertz, the highest frequency any amphibian species has been known to hear, the scientists report. Humans can hear up to about 20 kHz and typically talk at 2 or 3 kHz.
While most of the more than 5,000 frog species worldwide have eardrums that are flat on the side of the head, Huia cavitympanum has eardrums recessed in the side of the skull, similar to mammals.
Peter Narins, UCLA distinguished professor of physiological science and of ecology and evolutionary biology, and Victoria Arch, a UCLA graduate student in ecology and evolutionary biology, spent several nights in the remote area where the frogs live.
"We had very little information suggesting that they would be in this location," said Arch, lead author of the study. "We found them our first night out."
The study was published April 29 in the online journal PLoS ONE, a publication of the Public Library of Science, and is available at http://dx.plos.org/10.1371/journal.pone.0005413.
Huia cavitympanum produces some audible calls and others that are entirely ultrasonic.
"You look at the frog and can see it is vocalizing — you can tell because their vocal pouches pulsate — but you don't hear any sound. It's amazing," Arch said. "Then you look down at the recording equipment and see the lights flashing, indicating sound. I have never seen that before. In a frog, it's unprecedented to have purely ultrasonic vocalizations."
Narins and Arch have an idea about why the frogs, which live along a noisy stream, use both ultrasonic communication and calls that are audible to humans.
"Our hypothesis is that these frogs have shifted to use higher frequencies in their communication to avoid the interference of sound produced by rushing water in the lower-frequency range," Arch said. "However, high-frequency sounds do not transmit as far. By producing some lower-frequency calls, they can transmit calls over a greater distance, so they can communicate with frogs that are farther away. But by also producing some calls that are high-frequency — all ultrasonic — they may be able to communicate better over that background noise.
"Producing both types of calls might be a bet-hedging strategy to be heard," Arch said. "This is how males attract females, communicate with one another and establish territorial boundaries."
The research may have implications for improving human hearing aids and addressing hearing loss. Most hearing aids, Narins said, simply amplify sound, including unnecessary background noise. Better hearing aids that are directional, for example, could result from the research.
In 1998, Kraig Adler, a professor of neurobiology and behavior who had been Narins' professor at Cornell University, told Narins he should go to China to see "a frog with an ear canal like a human," Narins recalled.
Narins took the advice. Along with colleagues, including Albert Feng from the University of Illinois, Urbana-Champaign, he discovered a frog species that lives in rushing streams and waterfalls in east-central China called Odorrana tormota (formerly known as Amolops tormotus). Odorrana tormota, Narins found, could detect and produce ultrasounds due to the highly unusual presence of an ear canal. That research was published March 16, 2006, in the journal Nature.
The frogs in China produce very loud calls that are, at the same time, both audible and ultrasonic. In Borneo, however, Huia cavitympanum produces some sounds that are purely ultrasonic.
"That was unique — and the first time that has been found in any frog species," said Narins, who has studied dozens of frog species. "We are reporting this for the first time."
"With the Chinese frog species, every time you see the vocal sac pulsate, you will hear a sound," Arch said. "With the Bornean frog, sometimes you will see it is calling and you don't hear anything; it's all outside of our hearing range."
The frogs in China and Borneo's Huia cavitympanum are the only two frog species known to have recessed ear drums, Narins said.
In China, the scientists had set up a loudspeaker in the frogs' natural habitat near a river, then played frog calls and recorded the frogs' vocal responses with a microphone and very high-frequency equipment.
Later, they learned of this second species in Borneo with similar ear morphology. Narins and Arch went to Borneo in 2007, and Arch went back last summer.
In Borneo, they lived in a camp with a roof and three walls, with one side open. They slept on a wood floor, protected by mosquito nets. Narins was bitten by leeches and woke up several mornings soaked in blood. They ate noodles and peanut butter.
"It was a huge adventure, and so exciting to study the animals in their habitat," Arch said. "You feel like you're eavesdropping on them."
"There are not many places on the planet left that are so pristine and untouched by humans," Narins said. "It's exciting to go there and wonderful to have a sense of discovering something brand-new. We were there a week and saw only two other people."
Arch and Narins studied male frogs. In the majority of frog species, the females do not vocalize, and when they do, they do so less frequently than males, Arch said.
The research was funded by the National Geographic Society's Committee for Research and Exploration, the Paul S. Veneklasen Research Foundation, the National Institute on Deafness and Other Communication Disorders (NIDCD) of the National Institutes of Health, and the National Science Foundation (through a doctoral dissertation improvement grant to Arch).
Co-authors are T. Ulmar Grafe, a faculty member in the biology department at Borneo's University Brunei Darussalam, and Marcos Gridi-Papp, a UCLA postdoctoral scholar in Narins' laboratory.
The National Institute on Deafness and Other Communication Disorders supports and conducts research and research training on the normal and disordered processes of hearing, balance, smell, taste, voice, speech and language and provides health information, based upon scientific discovery, to the public. For more information, visit www.nidcd.nih.gov.
UCLA is California's largest university, with an enrollment of nearly 38,000 undergraduate and graduate students. The UCLA College of Letters and Science and the university's 11 professional schools feature renowned faculty and offer more than 323 degree programs and majors. UCLA is a national and international leader in the breadth and quality of its academic, research, health care, cultural, continuing education and athletic programs. Four alumni and five faculty have been awarded the Nobel Prize.
Atomic-level motion may drive bacteria's ability to evade immune system defenses
24.04.2017 | Indiana University
Two-dimensional melting of hard spheres experimentally unravelled after 60 years
24.04.2017 | University of Oxford
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences