THE TALK BETWEEN OCEANS
In our recent posts I explained how cetaceans hear and listen to their surrounding, mapping and creating their world and all that's within - their key to survival.
Whilst one group of whales, the toothed whales, use echolocation for communication and navigation, the second group of whales, the baleen whales, has evolved a whole different strategy:
Baleen whales instead use really low frequencies, in some cases too low for us to hear. These acoustic signals sound more like a rumbling or low moaning but as low frequencies travel way further than high-pitched sounds, baleen whales are able to communicate over great distances, 1000 of kilometers at times.
Scientists believe that they may use bone conduction as their main method of hearing as unlike toothed whales, they're not equipped with fat bodies in their lower jaw that would transmit sound vibrations to the inner ear. Neither are baleen whales capable of echolocation.
Long distance communication happens generally in the so-called SOFAR channel, where sound travels the fastest and furthest with the least transmission loss. However, this deep sound channel is not just used to talk to individuals in a far distance, but also to navigate: the animals emit sounds and as they listen to the echoes that are bouncing off the coastline and distance ocean shelves, they're able to map the area they're swimming in - finding their way back and forth over and over again when migrating between their feeding and breeding grounds- and that, even though they might have to wait as much as 20 minutes for an echo to return.
- Sarah