The power of nature’s sonar
Echolocation for cetacean navigation
I need no more convincing that the ocean is one of, if not the, greatest example of how sublime life is. How humbling. How ephemeral. How connected it is.
Around 70% of Earth is ocean. It’s where life began and where most of it still lives. Some of the world's smallest animals live there, alongside the biggest ever. The anglerfish is born bioluminescent so it can lure its prey in the depths. Sea anemone’s offer up their poisonous tentacles to clownfish as protection in exchange for a free parasite cleanse. Pregnant sea turtles return to the exact same beach they emerged from as hatchlings to lay their own eggs.
I need no more convincing that the ocean is a perfectly created symbiosis. My cup runneth over with proof. Incredible designs of evolution unfold everyday and that includes nature’s sonar. Echolocation.
Some dolphins, some porpoises, and all toothed whales use echolocation. They need it. They need it to hunt, for self-defence, to navigate their habitat, to avoid predators, to determine friend from foe, to communicate in the pitch black and across great distances.
Echolocation occurs when an animal emits short bursts of sound waves at various frequencies - around 200,000 hertz for whales. These waves are then reflected back to the animal if/when they bounce off an underwater object telling them how close or far the object is and sometimes exactly what it is i.e. grub or not grub. Hearing is the strongest sense for all cetaceans and because sound travels five times faster in water than in air, echolocation is an extremely effective way for them to navigate the vast oceans.
Most cetaceans use echolocation, but not necessarily in the same way. As the favourite prey of an orca - what could be worse - harbour porpoises have developed the ability to make rapid, high-frequency clicks to one another that orcas cannot hear, aiding them in their evasion. Amazon river dolphins use echolocation to steer the underwater terrain and obstacles often caused by seasonal flooding and many toothed whales have crafted a concentrated sonar beam to target their fast moving prey.
Echolocation develops in animals who live in dark or murky habitats to compensate for their inability to see clearly. It occurs through rapid vibration in the nasal passage. Toothed whales, dolphins and porpoises force air through this small opening causing their specialised organ, the dorsal bursae, to vibrate and collide producing clicks, chirps, whistles, and squeals. These sound waves then travel into the forehead of the cetacean where the melon1 focuses the sonar beam in the right direction while stopping impedance from the surrounding water.
Any reflected sounds echo back to the animal and are detected through their lower jaw and up to its ear. As these sounds are so loud and powerful the ears of cetaceans are shielded to protect them from the reverberation. So nifty are these cetaceans at echolocation that some dolphin species can detect small objects from the length of a football pitch away – even differentiating between species!
An excellent effort from the dolphins, however, coming in first place to reign supreme at the echolocation olympics is the mighty sperm whale.
Since echolocation is all about the nose and the size of the melon, it’s no surprise that sperm whales are the very best. In fact, they’re capable of producing one of the loudest sounds in the animal kingdom at 230 decibels2. The clicks of a sperm whale are so powerful they could easily blow out your eardrums and even vibrate a human body to death…I’m quite sure that’s never actually happened but it certainly gives an idea of just how loud they can be.
Their large noses take up around one quarter of their entire body and the spermaceti fluid in their melon, that they were once hunted for, is now believed to be a powerful tool they manipulate to perfectly focus this sound beam in any direction. Sperm whales spend a lot of their time diving deep for a squid snack so having this ability is just another example of the harmony of unperturbed ocean life. They use echolocation in the dark bathyal3 waters to seek out prey and some evidence suggests they can even stun their target first but this isn’t yet confirmed.
Not all sperm whale clicks are for hunting though, a recent study identified four variants of clicks. The long-range sonar is most often used, while the creaky sounds are for close range when a catch is imminent. Slower clicks are believed to have something to do with mating as they are only made by the males and finally, “codas” are distinct patterns usually heard when the sperm whales are socialising. These distinctions in clicks have led to some exciting research as they show that different groups of sperm whales communicate with a different repertoire. Hinting at the idea of unique voices and a culture among the sperm whales.
I need no more convincing that the ocean is the greatest example of how sublime life is. Echolocation tells me that.
If you can imagine the shape of a beluga whales head you can probably guess why they call it the melon. Sorry belugas.
For reference, a rocket launch is around 140 decibels.
The bathyal zone is a part of the ocean which extends from 1000 - 4000 metres below the surface.
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Amie 🐋
ECHOOO!....Echooo......echoo