Beyond Love Songs: The Sonar Hypothesis

Mercado’s research, culminating in his forthcoming book, Why Whales Sing? (Johns Hopkins University Press, November 4, 2025), posits that humpback whale song functions as a sophisticated form of sonar. This “sonar hypothesis” directly contradicts the prevailing “reproductive hypothesis,” which has dominated whale song research for over 50 years. The reproductive hypothesis suggests that these elaborate vocalizations are primarily used by males to attract mates, akin to the displays of peacocks or songbirds.

But Mercado’s decades-long investigation reveals a different picture. His initial skepticism towards whale song, as a young researcher in the 1990s, transformed into a consuming curiosity after encountering research on echolocation. He began to question why scientists hadn’t considered the possibility that whale song, despite its complexity, could be a method of environmental exploration.

“What I’m arguing is that singing whales aren’t performing, they’re exploring,” Mercado explains. “They aren’t ‘singing’ to serenade a potential mate but are instead vocally scanning to ‘see’ what’s going on for miles around them, using their songs as a kind of sonar.” He likens the process to a submerged megaspider weaving an acoustic web, mapping its surroundings through sound.

This isn’t to say that whales don’t communicate. However, Mercado’s evidence suggests that the primary function of song isn’t reproductive. He points to the lack of demonstrable female interest in singing males – in fact, females often actively avoid singers. Furthermore, singing males don’t exhibit the aggressive territoriality typically associated with courtship displays; they readily tolerate, and even accompany, other males.

A History of Dismissal

Mercado’s ideas haven’t been readily accepted. He faced significant resistance from the scientific community when he first proposed the sonar hypothesis 30 years ago, even being described as “verbally stoned” by his peers. His initial attempts to publish his findings were rejected, highlighting the entrenched nature of the reproductive hypothesis. However, persistent research and accumulating evidence gradually shifted the narrative, paving the way for the publication of Why Whales Sing?

Early research in the 1970s hinted at the possibility of echolocation in humpbacks, but these observations were largely dismissed because whale song didn’t resemble the clicks used by dolphins, the most well-known underwater echolocators. Mercado’s work demonstrates that echolocation can manifest in diverse ways, and that the complexity of whale song doesn’t preclude its function as a sensory tool.

The scientific community’s initial reluctance mirrors the historical dismissal of other groundbreaking ideas, such as the theory of evolution by natural selection. As Mercado notes, echoing Max Planck, scientific progress often occurs “one funeral at a time.”

What implications does this new understanding of whale song have for marine conservation? If whales rely heavily on acoustic mapping, increased noise pollution from shipping and sonar could significantly disrupt their ability to navigate, find food, and maintain social cohesion. NOAA provides extensive resources on the impact of ocean noise on marine life. Further research is crucial to mitigate these threats and protect these incredible animals.

Could our understanding of animal communication be fundamentally flawed? And what other hidden sensory capabilities might be waiting to be discovered in the natural world?

Learn more about Eduardo Mercado III’s work at the University at Buffalo Department of Psychology.

Frequently Asked Questions About Whale Song