Scientists in the United States recently described the incredible sounds produced by Weddell seals as they roamed under the ice of Antarctica. They chirped, hissed and cooed at sound frequencies inaudible to the human ear.
High frequency vocalizations
For these works recently presented in the Journal of the Acoustical Society of America, researchers fromUniversity of Oregon were based on two years of records collected by the Strait of Strait Underwater Oceanographic Observatory McMurdo. The analysis carried out revealed nine distinct types of ultrasonic vocalizations of seals up to 50 kilohertz (the range of frequencies audible to the human ear extending from 20 hertz to 20 kilohertz).
Evolving under the sea ice of theAntarctic, the seals Weddell use their long teeth to create air pockets. When foraging for food, consisting of groundfish, but also crustaceans and krill, these marine mammals can dive up to 600 meters and stay submerged for around 80 minutes.
While 34 types of seal calls (spanning a wide range of sound frequencies and all related to various social interactions) had been identified by the early 1980s, the new study relied on recordings of underwater vocalizations collected from 2017. For two years, the team used a wideband digital hydrophone, more sensitive than the equipment used previously and capable of picking up the high-frequency vocalizations of the seals.
” We identified many ultrasonic calls in the data and eventually found that the seals were using them quite regularly. », Note Lisa Munger, co-author of the study. ” The cries of Weddell seals moving under the ice create an almost unreal soundscape. You really feel like you’re in the middle of a space battle from a Star Wars episode », Underlines for his part Paul Cziko, who oversaw the research.
Different functions considered by researchers
According to the team, the seals could use this type of ultrasonic vocalization, which they likened to changing the communication channel, to stand out from all low-frequency noise, or for theecholocation, biological capacity used by other animal species to find their way or locate their prey.
” The possibility that seals use some kind of echolocation has been debated widely over the years. », Details Cziko. ” How they navigate and flush out their prey during the near-total darkness of the Antarctic winter remains a mystery for now. “
” We would also like to find out who is producing these ultrasonic cries. Whether it is males, females, young or representatives of the species as a whole », Adds Munger. ” Knowing how seals use these ultrasounds when hunting in deep water will involve more recording, so that they can be associated with behaviors. specific. “