Echolocation and the secret language of dolphins

Beneath the blue expanse of the ocean, a dolphin cuts through the water. It sends out bursts of high-frequency clicks — sharp pulses of sound that travel through the sea.

When those clicks strike a fish, a coral reef, or another animal, the echoes bounce back. By listening closely, the dolphin builds a detailed picture of its surroundings — not with sight, but with sound.

This ability, called echolocation, is like a built-in submarine radar system. Toothed whales (including dolphins) can detect the size, shape, distance — even the texture — of fish, rocks, or other sea creatures around them, all by listening to echoes.

Humans can’t hear these clicks — they’re too high-pitched. But for dolphins, this is how they navigate, hunt, and explore.

So that raises a big question: how does their brain make echolocation possible?

A new study, published in PLOS ONE, takes a step toward answering that by comparing the brains of echolocating dolphins with their non-echolocating relatives — baleen whales.

Not all whales echolocate. About 90% belong to the toothed whale group — including dolphins, orcas, belugas, sperm whales, and narwhals — which use echolocation to sense their surroundings. The rest are baleen whales, like humpbacks and blues, which rely on low-frequency sounds, singing, and other senses.

“Our research sought to understand how the pathways for auditory information differed between echolocating and non-echolocating whales,” says lead author Sophie Flem, an expert in marine mammals. “In humans, primates, rodents, and dogs, we have well-established maps of what parts of the brain contribute to what kind of processing. We don’t yet have those in dolphin brains, which are strikingly unusual compared to terrestrial animal brains.” 

The team zoomed in on a part of the brain called the inferior colliculus — a kind of crossroads where sound signals pass through on their way to more complex processing areas. It’s a structure that humans and most animals also have.

To study it, the researchers used high-resolution brain imaging on deceased dolphins and baleen whales that had stranded naturally. They followed the pathways sound takes as it moves through the brain toward the cerebral cortex — a region still largely mysterious in dolphins.

Low res rescue crew cv
Rescue teams assist stranded dolphins Wellfleet, Mass., a global hotspot for mass strandings of dolphins, offering rare research opportunities under federal protection. Image supplied.

They expected dolphin brains to have stronger sound-processing connections than baleen whales. But, to their astonishment, while the dolphins had more regions in their cortex connected to sound, those connections weren’t stronger. Instead, the biggest difference showed up further along the track — in the links from the inferior colliculi to the cerebellum.

Why does this matter? The cerebellum is best known for controlling balance and movement. But in recent years, scientists have discovered it’s also crucial for fast decision-making and predicting how the body and environment interact.

“Think about groping for a light switch in a dark room or using touch to figure out what object is inside a dark bag,” explains co-author Peter Tyack. “Dolphins use echolocation to interact with their world, and, unlike hearing and vision, they must produce the energy that then returns to their sensory receptors – echolocation is part hearing and part vocalisation”.

“Think about moving your hand to produce the touch sense feedback that lets you find the light switch. Similarly, dolphins move around their echolocation beam to get the feedback they need to function in a dark, underwater environment.”

In other words, echolocation isn’t something dolphins just receive — they control it. It’s active. They aim their sonar clicks like a flashlight and interpret the returning echoes in real time. That takes coordination between sound and movement.

“Comparative neurobiologists have longed to examine the patterns of connections within dolphin and whale brains for years, believing that the unique evolutionary history of these species will provide new insights into how brains evolve,” says senior author Peter Cook, an associate professor of Marine Mammal Science at New College of Florida. “The technology is finally there to start to crack open these mysterious nervous systems and find out how they tick.” 

“Now that we can opportunistically and ethically look inside these animals’ brains, they’re just getting started teaching us.”

The study opens a new window into how animals like dolphins may have evolved unique brain wiring to help them thrive in the dark, echo-filled underwater world.

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