Are you curious to hear how killer whales communicate? Our scientists present the sounds of these animals recorded by them for the first time.
The audio mainly contains pulsed calls, which are the social communication of killer whales. Other main types of sounds include whistles and echolocation clicks.
Interestingly, these predators do not use their vocal cords to produce pulsed sounds not with their vocal cords, and instead blow air through special structures in their nasal cavity. This mechanism, as well as the diversity 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 studies in Antarctica.
There are different ways to record sounds.
- For example, 24-hour passive monitoring in one location. It can be for a short period (for example, near Vernadsky, the sounds of Weddell seals were recorded during the mating season) or year-round (such a project is ongoing near Anvers Island, not far from 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 RV Noosfera, or motor boats during departures from the station. Although most often our biologists made recordings when boats stop to observe animals or perform other work. This is how the sounds of killer whales that you hear were recorded.
“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 an 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 type “B” (large) killer whales, which mainly hunt seals,” said Vadym Tkachenko, a biologist of the 28th UAE.
From the sounds, scientists determined that a group of at least three killer whales periodically came very close to the abandoned boat. They were probably looking for seals to eat.
“You can see killer whales in the area of our station infrequently, usually up to 10 times a year. At the same time, recordings decoding shows that killer whales are regularly present nearby, even when we cannot see them behind icebergs and ice masses,” explains NASC biologist Oksana Savenko.
The presented visualization contains spectrograms and oscillograms for 23 individual signals, mounted into a continuous track.
The spectrogram shows the frequency content of the signal at a specific moment in time (in kHz), and the oscillogram shows how the sound “pressure” changes for this signal (in µPa). The color intensity on the scale and spectrogram displays the volume in db.
The signals shown are very short. You can see from the time scale that they last tenths of a second, so for playback the track was slowed down to 10-12% of the original speed.
These signals are mostly in the ultrasonic range, which is not accessible to human perception. What we hear during playback are sounds that fall within the range of up to 20 kHz, as well as a set of various echoes and other environmental vibrations formed during animal vocalization.
Information is provided by Oksana Savenko and Vadym Tkachenko.
