Are Sperm Whale Clicks Dangerous to Humans?
A large mature female sperm whale swims with some smaller cetacean friends, a species called pygmy killer whales
INTRODUCTION
Sperm whales are the loudest animals on Earth, producing clicks powerful enough to travel miles through the ocean. But are these sounds deadly? Could a diver be harmed or even killed by a whale click? This post breaks down the science, the myths, and my firsthand experience after hundreds of hours in the water with these giants
What Are Sperm Whale Clicks? and Why Do They Make Them?
Sperm whales like many toothed whales produce clicks that are used to echolocate, detect objects and prey, and for communication.
Echolocation and “Seeing” in the Dark
Why do they click? The clicks serve multiple functions, the two main ones are communication and object detection. The latter serves two purposes, one is to see objects near and far, especially in the dark, and two, to find, locate, and hunt prey, again in the dark. The complex and highly refined system to produce clicks along with a large auditory processing part of the brain allows them to see what are likely very high resolution images of their surroundings, enabling them to effectively “see’ in the dark!
The Spermaceti Organ and Click Production
These clicks are produced in an elaborate collection of specialized organs and structures in the head of the sperm whale. Most notably and what gives rise to their name is the spermaceti organ. This fluid filled organ is the primary way sperm whales can control and amplify the clicks for different uses like foraging, and communication. Sadly it was the oil in the organ that made the sperm whale a highly prized species for the whaling industry. This light oil spurred on the industrial revolution.
How Loud Are Sperm Whale Clicks Really?
So this is where it gets really interesting and we will discuss the ongoing myth below. But first let's lay out the facts with a bit of math, and scientific rigor.
Firstly, we must recognise that science, and understanding science is really important for all things on the internet!
What 236 Decibels Actually Means
In the early 2000’s a team from Denmark retrieved data from a deployed hydrophone array in the cold waters off of Norway. To their surprise they recorded a single click at the level of 236 decibels, with a range of the highest recorded clicks between 228 and 236 decibels, and a total range from around 150-236dB. But here is where it gets important. These were measured as “dB re: 1 mPa rms”. What does that mean? Well this is effectively the units the sound was measured in. WHy is this important? Because when we measure this in air it is measured as - dB re: 20 mPa rms. The 20, is the important part. This makes comparisons between air and water decibel levels hard to correlate. A general rule of thumb is minus 61 dB from the in-water measurement to get the equivalent in air measurement. This is why scientific rigor is important. For it's like saying a temperature of 90 degrees fahrenheit, but ignoring that it is in fahrenheit, and leading people to believe it is in Celcius!
So effectively the equivalent in air loudness is around 170 dB. That is still loud, but not the brain exploding loud people have led us to believe. It would be very loud in person and if it happened next to you, probably even blowing an eardrum, but this animal was deeper than 600 meters when it clicked that loud! And this level was recorded once, and there have been little records of this magnitude since.
Can Sperm Whale Clicks Harm Divers or Marine Life?
The argument that sperm whale clicks can harm divers is one of mythology driven by some sloppy reporting and anecdotal claims by divers. The main culprit of this myth is James Nestor, sorry to call you out James. But he has gone on record in his book, and in public speaking events claiming the “sketchy” dangers of this 236 dB click, ignoring the rarity of it, and suggesting it will be able to kill you. Nevermind, the slight disregard for the importance of the units of measure (see above). And by coincidence one of his colleagues on an expedition with him, got a paralyzed arm for four hours after sticking out his hand.
A sperm whale approaches a photographer in the water, such close passes can be common if done with patience.
The Stunning Prey Myth
The other part of this myth, is the long held belief that sperm whales used thier clicks to stun/paralyse their prey. This is on the path of plausible, given that not only can they produce loud clicks, they can also focus, and change the intensity of their clicks towards an object. But what do data and science say?
The Truth from Tagging and Field Studies
Recently a paper published in Nature (Fais et al, 2016) examined this concept in detail. Some of the research highlights and their literature review were as follows. Firstly, experiments that attempted to examine the potential of sound stunning, or debilitating prey were unable to produce this outcome in fish or squid even above the 236 dB level. Secondly, acoustic tags attached to sperm whales revealed that during moments of high activity (hunting and catching prey), the clicks got quieter, faster, and closer together before going silent (the attack moment when the prey has been caught). This indicates the clicks are being used for locating prey, and the speed of the clicks linked to the need for increased precision before the strike.
Therefore, as it seems they don’t use the clicks to harm or stun their prey, it seems incredibly unlikely that there is any scope for them to use clicks to harm divers. Not only that, but they would have to use the highest level ever recorded, and be within a meter or two of a diver to induce that level of sound to cause any potential harm.
A Giant male sperm whale in deep blue water passes by, the scratches from past battles with squid clearly visible. If they were eto stun or kill their prey, there wouldn’t be so many scars on them
Real-Life Experiences: What It Feels Like to Hear a Whale Click
Clicks, Buzzes, and Tin Can Lids
What I have learnt and felt in the field is very different to the mythology. I have been clicked and buzzed by small and large sperm whales, even the giant males that “clang” instead of click. Imagine two tin can lids clanging together that’s what their clicks sound like. What I have observed and felt across all of these is a clear indication that the clicks aren’t extraordinarily loud, to the point where it’s rare to even feel it in your body at all. As they have come close to me, and buzzed me intensely, I’m yet to get a numb arm! This is after dozens of close-up encounters with whales within a few meters that have investigated me with incredible intensity and curiosity.
What Divers Really Experience
None of the people I have had in the water with me have ever experienced anything from these clicks except pure joy and amazement. The tears that have been shed are not tears because they can’t feel their arms, they are tears from having their mind-blown and being in disbelief that such an animal exists, and display such curiosity towards them.
Ultimately, my experience with these whales over the last decade and hundreds of hours in the water with them reveals that there is practically a zero-risk in any harm, pain, or damage to the human body from sperm whale clicks.
Are You at Risk When Swimming With Sperm Whales?
Lets not forget these are also very large and powerful animals. So from the audio side of things, no, there is no risk, but we must always respect these animals and let them dictate the outcome. In some parts of the word there have been instances of sperm whales hitting divers due to egregious behaviour from the divers. Chasing, crowding, trying to touch them or grab them, perhaps even separating mums and babies, in turn divers have been hit by the whales with their tails, and body. So, we must acknowledge that we are in their home, we are guests, and we must approach them with that level of respect, and then the risks of being harmed are diminished.
Swim With Us: Encounter Sperm Whales in the Wild
If this story sparked your curiosity, imagine hearing those clicks underwater for yourself. We run small-group expeditions to places where you can responsibly swim with sperm whales — always on their terms, and with respect.
Multiple Sperm whales swim at the photographer producing rapid click to scan them. Also heard is a louder slower click from another whale in the group.