Podcast Episode Summary

Podcast: New Books Network

Host: Gregory McNeff
Guest: Eduardo Mercado III, author of Why Whales Sing (JHU Press, 2025)
Date: November 11, 2025

Overview

This episode features an in-depth interview with Eduardo Mercado III about his new book Why Whales Sing, which challenges the widely accepted notion that humpback whale songs function solely as sexual displays. Mercado presents a bold alternative hypothesis: that whales might be using their songs as a form of long-range sonar (“biosonar”) to monitor the environment and track other whales. The conversation delves into the scientific, neurological, and philosophical dimensions of whale songs, exploring how human biases and scientific conventions shape our understanding of animal behavior, and why this matters for whale conservation.

Key Discussion Points & Insights

Author’s Motivation and Audience

• Motivations for the book:
  • The classic scientist’s “look what I found!” urge, but for a broad audience.
  • Raising public understanding about whale lives and the impact of human actions.
  • Target reader: “Anybody who's curious about animals and about scientific discoveries.” (02:26)

Style and Approach

• Mercado’s tone is intentionally accessible, balancing scientific depth with readability.
• Describes the book as “part persuasive essay, part scientific tutorial, and part party pooping polemic.” (03:29)

Background: Mercado’s Unlikely Path

• Electric Engineering to Cetacean Cognition:

  • Started as an engineer at IBM, shifted gradually to neuroscience out of curiosity about brains.
  • Ended up working with dolphins and humpbacks in Hawaii, leveraging coding skills before becoming genuinely interested.
  • “When I was first hearing these songs…this just sounds like a sick cow, basically…they were willing to pay me for it, so I was like, yeah, I'll do that.” (05:49–07:26)

• Repeatedly Drawn In:

  • After a stint away from bioacoustics, graduate students kept bringing him back, leading to decades of engagement with whale songs.

Current Scientific Consensus: Why Do Whales Sing?

• Display Theory:

  • The prevailing belief is that male humpback whales sing as sexual displays to attract mates or compete with other males.
  • “They would universally say that they're singing as a sexual display—specifically that it's males sexually displaying to other animals…to mate later on.” (13:37)

• Sex of Singers:

  • Almost all verified singing humpbacks are male; sample size is around 200.
  • Some ambiguity and possible bias in how singers’ sex is determined. (15:16)

• Choruses:

  • “Chorus” means multiple males singing within earshot, but unlike human choruses, these whales can be miles apart. (14:40–15:16)

Bioacoustics and Whale Song Structure

• Definition: Bioacoustics studies animal sound production, perception, and function. In whales, hydrophones are indispensable for gathering data. (16:33–17:26)
• Song Mechanics:
  • Whales sing in cyclical patterns (“units” and “phrases”), with each “song” comprising repeated sequences lasting minutes to hours.
  • No clear start or end point—much like a “merry-go-round.” (11:10–12:23)
• Complexity:
  • Mercado places more importance on the acoustic, rather than merely structural, complexity of songs.

Mercado’s Sonar Hypothesis

The Proposal

• Hypothesis: Humpbacks might use their songs as a form of biosonar, analogous to but distinct from bat or dolphin echolocation, primarily to perceive their distant environment and locate conspecifics.

• Key Quote:

  “When you see a humpback whale producing sounds in these rhythmic patterns…they’re putting out… sound fields to spread out from around them…and see how those sound fields interact with anything in the ocean within a certain range… Any large objects, like the size of another whale, would return echoes. By monitoring those echoes, they could potentially track other whales that are not going to be visible.” (18:17)

• Motivation:

  • Conventional theory doesn’t account for massive variability and morphing in song patterns—which make little sense as long-range communication signals but are consistent with exploratory sonar.

Evolutionary Rationale

• Baleen whales evolved in environments where vision was limited, and close relatives like dolphins developed biosonar.
• If baleen whales did not evolve such capacities, evolutionary theory demands an explanation why. (21:49–22:00)

Acoustic Physics of the Ocean

• Whale song propagates horizontally in relatively thin “discs” of water, more like a pizza than a deep dish—changing traditional intuitions about signal spread. (25:00–26:41)

Echolocation & Sonar: Definitions

• Echolocation: Any system where information is gained from echoes, whether for navigation, object identification, or spatial awareness.
• Sonar: Originally a technical term from the US Navy; physically equivalent to echolocation but human-made.

Addressing Major Challenges & Conventional Pushbacks

Why Mostly Males?

• Mercado disputes the certainty that only males sing, pointing to observational biases and underexplored contexts where females might sing.
• Proposes that intense male singing in tropical zones (where few females are in estrus at any one time) is due to the need for males to actively search for potential mates. (26:58–28:26)

Do Females Respond to Song?

• Field observations and playbacks show females do not typically approach singing males, contradicting the display theory.
• “Other males are the ones that mainly approach singing males…females seem to be…steering clear of singers.” (28:44)

Song Complexity and Steady Rhythm

• Critics argue that the songs are “too complex” and “too steady” to be sonar.
• Mercado counters that complexity is in the acoustics (not patterns), and that rhythmic pacing matches the physics of searching large volumes of ocean—like a bat’s long-range search pattern, not rapid attacks.
• “They're producing a sound, they're listening for a certain amount of time, which corresponds to the range…then…they make another sound. So they're basically maxing out their range by spacing out the sounds.” (33:52–35:08)

The Role of Silences

• Among his key insights: For whales, the silences between song units are critical; this is when they are listening for faint echoes.
• Quote:

  “What humans perceive when hearing these songs is not what the whales themselves hear…what humans perceives as being nothing means everything to singing whales.” (35:45–36:42)

Reverberation

• Whales use the reverberant “echo field” they create, potentially harvesting more information than they would get from simple, direct echolocation.

Whale Brains & Auditory Neuroscience

Humpback Neuroanatomy

• Humpbacks have brains as large or larger than humans, with extensive cerebral cortex.
• “They have more cerebral cortex than humans…But people don't really know what those differences actually functionally achieve.” (45:49–47:02)

Auditory Plasticity

• Humpbacks and humans are the only known mammals who continuously modify their vocalizations throughout adult life, indicating advanced auditory cortical plasticity. (47:29–49:09)

Intelligence

• In acoustic processing, whales likely surpass humans:

  “I would be surprised if cetaceans aren’t more advanced than humans are in terms of the way they process sounds…they need the sounds much more than humans do.” (49:23)

The Human Side of Science & The Scientific Method

Objectivity vs. Bias

• Mercado notes that the scientific method in practice is neither as purely objective nor as collaborative as is often portrayed.
• The tendency to interpret whale song structure hierarchically reflects more about human psychology and the history of science than about the whales themselves. (51:19)

Challenging Dogma

• Despite the rational evidence for his sonar hypothesis, Mercado's proposals have been dismissed or labeled as “pseudoscientific garbage.”
• Emotional, cultural, and disciplinary attachment to certain animals, like humpbacks, shape scientific arguments. (54:54–57:16)

Disciplines at Odds

• Biologists (focus: reproduction, evolution) dominate whale song research, while psychologists focus on cognition and individual experience, influencing their respective interpretations.

Wider Implications

Conservation Impact

• Understanding whether songs serve as sonar or display has direct consequences for whale protection:

  “We’re introducing all kinds of noise into the ocean that could dramatically affect a whale's ability to detect other whales. If they can’t…it's like throwing smoke into their lives…it could be a serious problem.” (61:57)

• Whale population collapse could impact whole ocean ecosystems—science here is not just an academic debate.

Notable Quotes & Memorable Moments

• On Motivation:

  “It's kind of like that 'look what I found' impulse… but in the scientific domain.” (02:26, Mercado)

• On Being Drawn Back into Whale Science:

  “I've tried to get out, and I keep getting drawn back in.” (07:43, Mercado)

• On Why Whalesong as Display Doesn’t Fit Observations:

  “There are basically no observations of females approaching a singing male…other males are the ones that mainly approach singing males.” (28:44, Mercado)

• On the Sonar Hypothesis:

  “Why would a whale that's trying to communicate with other whales at long distances produce signals that are this variable? It didn't make any sense to me.” (18:17)

• On Differences with Dolphins and Bats:

  “It's very different…in your head scenario…very different from what a dolphin or bat would have to deal with.” (43:41)

• On The Human Side of Science:

  “I feel like what I'm suggesting is actually more sophisticated than what they're suggesting…It's a weird mindset, but definitely, I think it's sort of…an emotional reaction…a barrier to a lot of progress…” (55:23)

• On the Real-World Stakes:

  “If whales can't find each other to mate, then it could be a serious problem.” (61:57)

Timestamps for Key Segments

• Author’s Motivation & Style: 02:20–03:48
• Mercado’s Background & Accidental Start: 05:49–07:26
• State of the Science (display thesis): 13:37–14:40
• Bioacoustics Explained: 16:33–17:26
• Whale Song Structure: 11:10–12:39
• Sonar Hypothesis Introduced: 18:17–20:52
• Evolutionary Context: 21:49–22:40
• Defining Echolocation & Sonar: 22:40–25:00
• ‘Pizza’ Analogy: 25:00–26:41
• Major Counterarguments & Mercado’s Rebuttals: 26:58–36:42
• Significance of Silences: 35:45–36:42
• Reverberation Explained: 38:00–39:42
• Whale Brain Plasticity: 47:29–49:09
• Scientific Objectivity Undermined: 51:19–52:58
• Emotional/Disciplinary Bias in Whale Science: 54:54–57:45
• Conservation and Broader Implications: 61:57–62:56

Takeaway

Mercado’s Why Whales Sing is not just a treatise on cetacean vocalizations—it’s a critique of scientific orthodoxy, a plea for intellectual humility, and an argument that the stakes of understanding whale cognition go far beyond academic debates. As noise pollution rises in oceans, grasping the true function of whale song becomes not just a question of curiosity, but of survival.