Above the water, they sound like roaring Wookies. Under the ice, they look like robots chatting and chatting. Either way, Antarctic Weddell seals should have no trouble finding work in the near future. Star Wars project.
“Weddell’s stamp calls create an almost incredible, alien soundscape under the ice,” Paul Cziko, a visiting professor at the University of Oregon and lead author of a new study describing the strange sounds of postage stamp. “It really sounds like you’re in the middle of a space battle Star Wars, laser beams and everything “.
The problem: you would have to be an alien (or droid) to hear them; all these science fiction sounds are totally inaudible to human ears.
Cziko and her colleagues were able to detect otherworldly noises after two years listening to Weddell’s seals (Leptonychotes weddellii) with a special hydrophone (an underwater microphone) installed at McMurdo Sound in Antarctica in 2017.
Before researchers began recording, scientists knew about the 34 calls for audible stamps for human ears. Now, the team’s research, published Dec. 18 online The Journal of the Acoustical Society of America – Adds new types of ultrasonic calls to the stamps repertoire. These sounds include trills, whistles, and breasts from someone else’s sleep, sometimes composed of multiple harmonized tones.
Humans hear between 20 and 20,000 hertz (or 20 kilohertz), the researchers noted. Most new stamp sounds exceeded 21 kHz, and some steadily increase to 30 kHz.
(McMurdo Oceanographic Observatory)
At the top: visual representation (spectrogram) of one of the nine types of ultrasound calls. The U-shaped features of the top half of the frame are part of the U101 call type.
A high-pitched whistle reached a 49.8 kHz shout, the team wrote, and when the labels harmonized several tones, the resulting noise could exceed 200 kHz. (This is far beyond the hearing of cats, dogs and even some bats.)
What are all these high frequency communications about? Researchers are not sure; until now, scientists had never detected ultrasonic vocalizations in seals (nor in any other fin-footed mammal, such as sea lions or walruses).
An Antarctic McMurdo sound diver observes a Weddell seal. (McMurdo Oceanographic Observatory)
According to Cziko, the sounds could only be additional elements of conversation to “highlight above all the lower frequency noise, such as switching to a different channel to communicate.”
Theoretically, it is possible that noises are involved in echolocation, the biological sonar used by animals such as dolphins and bats to be found in dark places. But so far there is no evidence to indicate that seals use echolocation, the researchers said.
However, the behavior would not be at all characteristic of seals that can dive more than 600 meters underwater and hunt in the darkness of the Antarctic winter, the team added.
Let’s see if a Wookie tries to do that.
This article was originally published by Live Science. Read the original article here.