Ukrainian polar explorers recorded unique sounds of killer whales in Antarctica

 Ukrainian polar explorers made a unique recording of orcas. The audio mainly contains impulse cries, which are used for social communication of these animals, UNN reports with reference to the National Antarctic Scientific Center.

On February 10, 2024, we were working in Collins Bay and saw 11 leopard seals on the ice floes. So when we landed on the island, we left the acoustic recorder turned on near the moored boat so as not to miss the opportunity to record the underwater vocalizations of these predators. But then the recording unexpectedly revealed the sounds of a group of "B" type killer whales (large), which mainly hunt seals 

According to the sounds, the scientists found out that a group of killer whales of at least three animals periodically approached the abandoned boat very closely. They were probably looking for seals to feast on.

Seeing killer whales in the area of our station is not often possible, usually up to 10 times a year. At the same time, deciphering the records shows that killer whales are present nearby regularly, even when we do not see them behind icebergs and ice accumulations 

According to the National Antarctic Scientific Center, the presented visualization contains spectrograms and oscillograms for 23 individual signals, assembled into a continuous track.

The spectrogram shows the frequency content in the signal at a specific point in time (in kilohertz kHz), and the oscillogram shows how the sound "pressure" changes for this signal (in micropascals µPa). The color intensity on the scale and the spectrogram itself reflects the loudness in decibels (db).

The given signals are very short. On the time scale, you can see that they last tenths of a second, so the track was slowed down to 10–12% of the original speed for playback.

These signals are mainly in the ultrasonic range, which is not accessible to human perception. What we hear during playback are sounds that fall into the range up to 20 kHz, as well as a set of different echoes and other environmental vibrations that were formed during animal vocalization.

Let's add

In addition, as reported by the National Antarctic Scientific Center, the main types of their sounds include whistles and echolocation clicks.

It is interesting that these predators create impulse sounds not with vocal cords, but by blowing air through special structures in the nasal cavity. This mechanism, as well as the variety and functionality of the sounds of killer whales and other marine mammals, has not been fully studied. Therefore, our biologists pay special attention to such acoustic research in Antarctica.

There are different ways to record sounds.

• For example, round-the-clock passive monitoring in one location. It can be for a short period (for example, near "Vernadsky" they recorded the sounds of Weddell seals during the mating season) or year-round (such a project is currently underway near Anvers Island near our station, in cooperation with American colleagues). Such monitoring allows us to determine the seasonal dynamics of the presence of different species of marine mammals in this area. 
• Another option is acoustic trawling during the movement of ships, in particular the Noosphere, or motor boats during sea voyages from the station. Although most often our biologists made recordings during boat stops to observe animals or perform other work. This is how the sounds of killer whales that you hear were recorded.