Listen: Sperm whales’ echolocation sounds are much more than just underwater clicks

Listen: Sperm whales’ echolocation sounds are much more than just underwater clicks

I was fortunate enough to get to see a small pod of sperm whales off the southern coast of New Zealand in 2018 while out with a whale-watching tour, and even more fortunate to obtain a recording of the whales with a hydrophone as we photographed them. For the average listener, the resulting sounds I captured seem to be only a series of almost mechanically recurring clicks.

These sounds are part of the whales’ echolocation faculties, their ability to see underwater for phenomenal distances—sometimes to communicate, but most often to locate and consume their prey. And in addition to being dense sounds whose returning bounceback signals convey rich information to the whales’ brains, they are also incredibly powerful sound bullets capable of disorienting and possibly even incapacitating their prey.

A fascinating Smithsonian piece from 2011 explored how sperm whales’ echolocation functions. The sounds are produced primarily from the very same organ—a functional sound lens atop their skulls that comprised primarily of the extraordinarily fine oil that fueled the Industrial Revolution—that was the main target of the whalers of the 19th and 20th centuries who pursued them to near-extinction.

Biologists now believe that the sperm whale’s massive head functions like a powerful telegraph machine, emitting pulses of sound in distinct patterns. At the front of the head are the spermaceti organ, a cavity that contains the bulk of the whale’s spermaceti, and a mass of oil-saturated fatty tissue called the junk. Two long nasal passages branch away from the bony nares of the skull, twining around the spermaceti organ and the junk. The left nasal passage runs directly to the blowhole at the top of the whale’s head. But the other twists and turns, flattens and broadens, forming a number of air-filled sacs capable of reflecting sound. Near the front of the head sit a pair of clappers called “monkey lips.”

Sound generation is a complex process. To make its clicking sounds, a whale forces air through the right nasal passage to the monkey lips, which clap shut. The resulting click! bounces off one air-filled sac and travels back through the spermaceti organ to another sac nestled against the skull. From there, the click is sent forward, through the junk, and amplified out into the watery world. Sperm whales may be able to manipulate the shape of both the spermaceti organ and the junk, possibly allowing them to aim their clicks. The substance that made them so valuable to whalers is now understood to play an important role in communication.

As the article explains, sperm whales mainly use this powerful sixth sense to locate their prey, which is primarily comprised of large squid, including in some cases the giant squid who live deep in the oceanic trenches to which the whales are among the only marine mammals capable of diving. The whales we saw off the coast of Kaikoura in August 2018 were apparently seeking such prey down in the Hirukangi Trench, which in places is 9,000 feet deep.

Sperm whales’ ability to dive to extraordinary depths is enhanced by the deep wrinkling in their skin, which is visible on their dorsal fins when they come to the surface to breathe.

At one point, scientists wondered if their echolocation sounds functioned to stun or incapacitate the squid, and perhaps even to crush them into submission, as powerful sounds underwater are known to be capable of doing. However, further research into the question found nothing to support the hypothesis.

“This was a lovely idea killed by data,” Peter Tyack, a senior scientist at Woods Hole Oceanographic Institution in Massachusetts, told NYU’s Scienceline. Tyack and another scientist conducting separate experiments found that sperm whales’ ultrasonic noises didn’t affect squid or fish.

However, it’s still likely that the sounds play a role in their ability to overtake their prey:

So ultrasound as a weapon is out. But there is a loophole. Sperm whales make some other powerful sounds that weren’t tested. These other noises are within the range of human hearing and much lower in frequency than the ones used in the two studies. However, researchers disagree on whether it’s still worth testing the hypothesis that sperm whales are sonically armed and dangerous.

“I don’t think we should pitch out [the] theory just yet,” said Ted Cranford, a sperm whale anatomist and professor of biology at San Diego State University. “It might be pretty easy for the sperm whale to overload the sensory system of some critter.”

Listening over the hydrophone, it was clear to me that the whales’ echolocation sounds are extraordinarily powerful. I’m accustomed to hearing the echolocation sounds produced by killer whales (there are plenty of samples in this recording), which are shorter and less dense. If nothing else, the sounds clearly are capable of traveling tremendous distances underwater. And who knows what they are telling the whales?

Sperm whales’ powerful surface blows also enable whalers in the 19th and 20th centuries to spot them and nearly drive them to extinction.

From Daily Kos at Read More. This article is republished from DailyKos under an open content license. Read the original article at DailyKos.

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