Calls Beyond Our Hearing

Unlocking the Secrets of Animal Voices

Holly Menino

St. Martin's Griffin

1
Sheila Jordan and the Mockingbird
 
 
This book begins with a concert and, three years later, a horseback-riding accident. The concert was a vivid experience of a woman’s singing, and it impressed on me what a powerful and pliant tool the voice is. The riding accident left me with a grade 3 concussion and an uncomfortable awareness of how fragile perception is.
First, the concert. In the summer of 2002 I am sitting in the audience for a concert that caps off the Jazz in July workshops at the University of Massachusetts in Amherst. Outside the hall, the afternoon is hot and sunny. Inside, where the tall windows are open to catch what breeze there is, the stage is black. Black curtains, black piano, a drummer lurking over a black trap kit, and the man playing bass tipping back into the darkness with the long stem of his instrument. All of us in the audience are here to listen, and we are focused on this darkness when Sheila Jordan takes her place on the stage. She has been teaching at the university all week, and the morning found her in the audience, listening intently to students as she scribbled notes. Now it is her turn. She finds the mic and takes a tall stool near the bass player.
Jordan has attained a high perch in the jazz world and, now approaching eighty, seems entirely matter-of-fact about the task at hand. “I’d like to dedicate this song,” she says quite innocently, “to President George Bush.” With the mic in her hand, she marks off a bar’s worth of tempo for the three other musicians. The song is a standard, one that is interpreted by everyone, and she begins it the way it is often begun, slow and sexy or, at least, sensual:
I’d like to get you on a slow boat to China,
All to myself …
Alone.
There is something sinister in the way she isolates the last word and pressures the note with a tiny fluctuation of pitch. The note and the words it carries could have been tender, but they are somehow savage. Whatever she has in mind for the president isn’t pleasant.
The slow boat to China is taking the president someplace dangerous. We can well imagine the tortures George W. Bush is enduring in Sheila Jordan’s arms. Nervous titters run through the audience, and I am beginning to feel sorry for the president. But I am also laughing as openly as the people sitting around me. Her voice has such power that just a tiny wiggle in it can override language and stand meaning on its head. Her target is the president, but it could just as well be someone or something else. Inflection, the twisting of pitch and stress, is something we use to make a point or highlight a phrase in a joke on our way to the punch line. But song is a conspiracy of language and music, and not many of us have the vocal skills to bring inflection to song. Sheila has the chops to inflect melody and words at the same time and to elevate the result to art.
She pauses to let the piano player get in, and the keys speak so quietly that a sound from outdoors can be heard clearly. It is the backup beep of some kind of construction vehicle. The beep is loud, insistent. It cuts through the drums and bass, but the musicians ignore it. A big construction project has been going on in the center of campus, and I thought the digging was a half mile away in another group of campus buildings. But the backup beep sounds right outside the window, and for the musicians, there is no way to deal with the interference except to play through.
Jordan comes back in on the chorus, scat singing. No words, just syllables and notes. Leaving language behind, she responds to the piano, warbling in and out of the scale, sliding through half pitches, flying up through the octaves, then swooping down silently to snatch up the notes of the bass. Mimicking the songs of the other instruments, she repeats their phrases without actually replicating them, and she sneaks off with their rhythms and punches them up to make wilder, rougher phrases of her own. At some mysterious psychological and emotional level, her scatting says more about what might happen to George W. Bush than she had been able to imply with her dangerous melodic skewing of the lyric. Her song calls up violence, a bumbling victim, slow murder. It is a remarkable demonstration of the physical and expressive capabilities of the human voice.
The beep, the irritating beep, continues.
After the concert, we pause on the steps leading down from the hall, and the beep is still sounding, regular and mechanical. But I can’t see any construction or any equipment. My first impression was correct. The excavation is going on in the midst of a neighboring cluster of buildings. The beep, however, is coming from a tree at the side entrance to the hall. I look up into the branches, and after a few moments, the beeper reveals itself with a flap of gaudy white wing bars. A mockingbird. The bird is still for a moment, and I can hear a fainter beeping from the excavation site. The feathered master mimic is responding enthusiastically to a backhoe. The call coming from the leafy inner spaces of the tree is not perfect in its imitation of the call of the backhoe, but it is convincing. The bird is good, as good at what he does with his voice as Sheila Jordan is with hers.
His is another forceful voice. The mockingbird is pouring all his energy into his singing, but his song doesn’t affect me the way Jordan’s did. I don’t understand it the way I understood hers. In fact, I don’t understand it at all. Of course not. I am not—none of us humans are—the right audience for a mockingbird. The bird has his own audience in mind, other mockingbirds and other animals that inhabit his world, and you and I don’t communicate in that world.
Sheila’s song stays with me the way music can, returning to your mind in snippets, sometimes obsessively in the middle of the night when you wish it would go away and let you sleep. But I don’t think much about her song until after the accident.
I have kept and ridden horses all my life. I like to be around them even when I’m not riding, like to take care of them, to watch them socialize and play in the pasture, touch muzzles and take in breath from each other. I enjoy trying to read them and also to read my dogs, trying to figure out what is going on in their heads. The day of the accident there is not enough going on in my own head. I am not thinking clearly, because only forty-eight hours earlier I was undergoing minor surgery. Maybe I’m hungover from the anesthesia. Whatever the cause, I don’t feel right but manage to convince myself I am back to normal. I go to the pasture and bring the horse up to the barn. Stupidity is a major cause of accidents.
I have had the mare for several years. I was one of the first people on her back. I have brought her along through the basics and am beginning to work on more advanced moves. I know she has some life and a tendency to spook. As I say, stupidity creates accidents. When she spins, the legs I usually have on her are gone. Zero. I don’t make any effort to stay with her, and I’m on the ground. If anywhere in your childhood reading you have learned that a horse will do anything to avoid stepping on a human, throw that bit of knowledge out the window. A horse is an animal of flight, and you do not want to be in the flight path. I am trampled and spun out from under the mare by her heels. Examining table, X-ray, MRI. Rest.
My ears and eyes don’t seem to be working in synch. My perception and balance are out of phase. I am walking around on the fun-house floor, and I worry about my hearing. While the dizziness lingers a kind of reverse paranoia sets in: I am not hearing voices, and I am suspicious of silence. I become intensely aware of sounds that never reach me intact. There are plenty of these—fragments of conversations lost to din, the vocal undercurrents that precede a dog’s growl, the louder breathing of a horse about to nicker, the slight grace notes that introduce a bird’s call. I have always enjoyed sound and the way notes or words pass in and out of my awareness. But there hasn’t been much of this awareness since my head banged down in the dirt.
Maybe I’ve stopped tuning in, maybe I’m no longer listening well. In college I was a music student, so I am aware I have a number of different modes and degrees of hearing, levels of intensity in paying attention. The same is true of the ways I attend to language. When someone speaks to me, sometimes what I hear is a stream of sound from which I extract information—opinions, gossip, instruction—other times what I hear are the qualities of the voice delivering the words. It’s much the same with written language. Sometimes when I read or write I hear the words resounding in my head as if someone had actually spoken them. But sometimes when I read, the words are just icons on the page, waiting to deliver a fact or two. Now all the varieties of my awareness of sound have somehow moved into the background, as if the recording engineer has dialed down the knobs, and sound doesn’t seem to register completely.
For months I walk through my routines in a woozy bubble and worry about the possibility of now-dimmer sound decaying into silence. It is during this period that I revisit the experience of Sheila Jordan and the mockingbird, and I begin to read about and reflect on their two voices.
Bird voice. Human voice. What’s the difference? And why should this matter to you?
Your voice is the most powerful social tool that comes into the world with you. You use it to negotiate every transaction, from the simplest I Want to the most complicated How Can I Possibly Explain This? I have found that in even the meanest bouts of insomnia the best antidote is the sound of another person’s voice, and I think it’s probable that crisis center hotlines are a result of the same phenomenon. The voices of other people have great emotional power, and if you think about the most moving events and the most intimate moments in your life, you probably recall in these experiences the voices of certain people. The voices of our own kind accompany our births, our deaths, and all the growing and learning, the attachments and separations, the fights and reunions and successes and losses that stretch between our first and our last. The same is true for the mockingbird and for other animals.
A central fact about the vocal communication of any species is that voice stands in for touch, for physical contact. AT&T used to urge us all to “reach out and touch someone.” And in fact, it is comforting to say, “I love you,” to someone at the other end of the line when you can’t physically hold that person. The substitution of voice for touch works just as well when aggression comes into play. It’s so much easier and safer to say, “I ought to punch you out!” than to actually risk taking a poke at the offender. We say, “Keep in touch,” when we really mean “Keep telling me things,” and that’s why slamming down the phone causes such unsettling emotions to the people on both ends of the line. That is why it is so difficult to be mute or deaf.
In reading during my dizzy uncertain period, I discover that this is also the way things work in the animals’ worlds. But the contexts, the places they live and their perceptual environments, are quite different. Since the 1930s scientists have been eavesdropping on quite a number of animals to find out how, exactly, animals use their voices to negotiate their lives. Right now the scientific literature is flush with new findings and new theories about animal voices, and one assumption behind all this science is that the more you know about the mockingbird’s song and its sources, the better you will understand Sheila Jordan’s song and your own. So the real question about bird voice and human voice is not, What’s the difference? but, What’s the same?
On one level it isn’t hard to pick out what Sheila has in common with the mockingbird. The mockingbird has a vast repertoire and an impressive range. Just like Sheila Jordan. It is also a fabulous mimic and shares this talent with Sheila, whose mimicry is most obvious when she scats, when she sings without words. She is copying, within her own vocal range, the tones and pitches and colors of “Slow Boat to China” and the sounds of the bass and the piano. When she reaches beyond the notes prescribed by the melody and the rhythm, she adds something very like the bubbly passages the mockingbird uses to connect the phrases it dutifully replicates. What she and the mockingbird share is mimicry, repetition of sounds in phrases, and rhythm, the spacing over time of sounds and the silences between them. These are fundamental elements of both birdsong and music, as a good deal of trite poetry points out. These are what you expect when you listen to music.
Audience expectation drives music and speech, and in fact, it is what empowers any use of the human voice. We sit down to listen to Sheila Jordan with a certain set of expectations about how her voice will fit with the melody, the rhythm, the lyric. Sometimes the musical passages that move us most strongly are the ones that thwart our expectations. We have other expectations when we speak with someone. There are rules of conversation like Keep Still While the Other Person Speaks and The Question Comes Before the Answer. Do animals have rules of expectation about repetition, patterns, and mimicry? And if they do, what does that imply about the biological and cognitive sources of our vocalizing and our expectations? Are these innate impulses or do we learn them?
Looking into these questions, I discover that animals as simple as insects communicate by audio. They have auditory organs, and insects such as crickets and cicadas have percussion sections, parts and pieces they can clap and scrape together. But what it takes for an animal to produce what we think of as “voice” is a backbone. What it takes to sing and to be part of an audience is real spine. Only vertebrates have a voice box add-on to their respiratory tracts—a larynx in mammals or, in the case of birds, a syrinx—that allows them to call and to sing. They all have some version of our eardrum and neural transmission. For the time being, let’s just say we’re using the same basic tools as other animals with backbones. When Sheila Jordan sings, her voice is created when the air she breathes out meets and pushes through her larynx, causing her constricted vocal cords—she has caused this construction because she intends to sing—to vibrate. The vibrations of her vocal cords emerge as sound. With some modifications adapted for the animal’s habitats, this is essentially the way all mammals and birds produce vocal sound. Air from the respiratory system is pushed out through the folds of membrane we call the vocal cords, a resonating organ. In the case of a lion, this organ is the larynx, in the case of a red-winged blackbird, a syrinx, and in the case of a dolphin, a vomer and nasal air sac. The bat has a heavily muscled larynx that can squeeze tightly enough to produce ultrasound. The blackbird has dual membranes, one in the airway from each lung, and this doubling of pipes accounts for some of the fluidity and complexity of its song. A dolphin’s blowhole substitutes for a pair of nostrils. It closes involuntarily, and the dolphin controls the flow of air from the nasal air sac by voluntarily opening the blowhole. The muscle that controls the opening of the blowhole allows a broad range of air pressures and variety of sounds, and it is thought that the dolphin uses the mound of fatty tissue on its forehead, called a melon, to bounce the sound of its voice in different directions.
We and the rest of the vertebrates have some common devices for collecting and transmitting sound to our brains. The essentials of this system are a tympanic membrane—a “drum”—and its reverberations transmit the sound vibrations through a tubular channel to sensory appendages, hair or papillae, where sound vibrations meet nerves that translate them into electrical signals that travel through the nervous system to the auditory brain. Quite often, as in the human and the bat, there is the fleshy structure on the outside of the head, a horn for gathering in sound. This is what we usually think of as the “ear.” But this external ear is not necessarily standard equipment. In the frog it is absent, and the tympanic membrane is exposed on the side of the head. In dolphins and whales, fat tissues in their jawbones transmit sound to the inner ear. We’re more adept at some aspects of hearing and vocalizing than animals, and they are more adept at others—in fact, some of their abilities are extreme.
Take, for instance, the bat, a member of our own family, the mammals, and so not that far removed from us. In an early investigation of what abilities separate the animals from us, the Italian abbé Lazaro Spallanzani came upon a mystery that would go unsolved for 140 years. Spallanzani served as a professor at the universities of Reggio, Modena, and Pavia, and he was an enthusiastic collector of natural phenomena. In 1793 while harboring an owl and a bat in his rooms, he began a series of nighttime experiments to determine how nocturnal animals make their way in the dark. First he released the owl in his darkened room and was surprised to find that the owl collided with objects in the room. Next he released a bat, which navigated handily among the books and candlesticks. Thinking that perhaps the bat had extremely acute night vision, Spallanzani then covered the heads of a number of bats with hoods. Some lost their ability to navigate in the dark, others did not, and this prompted Spallanzani to launch a round of experiments in which he covered different portions of the bats’ heads.
At last, seeking to rule out the bats’ use of their eyes for navigation, the abbé blinded the animals by rather gruesome means and waited for them to recover. After encouraging one of these subjects to fly again, he reported, “During such flight we observe furthermore that before arriving at the opposite wall, the bat turns and flies back dexterously avoiding such obstacles as walls, a pole set up across his path, the ceiling, the people in the room, and whatever other bodies may have been placed about in an effort to embarrass him.”
Throughout his experiments, Spallanzani kept up an assiduous correspondence about his bat observations, and he urged colleagues at institutions throughout Italy and France to try to capture bats living near them and repeat his experiments. A French surgeon, Charles Jurine, heard Spallanzani’s first letter read aloud at the Geneva Natural History Society and, taking up the challenge, repeated Spallanzani’s experiments. Reporting immediately to the abbé, Jurine added an important observation: if the ears of the bat were plugged, it crashed helplessly into objects in its path.
Spallanzani was skeptical about the proposition that “the organ of hearing appears to supply that of sight in the discovery of bodies.” “How, if God love me,” he asked, “can we explain or even conceive in this hypothesis of hearing?” Nevertheless, he pursued its proof with some ingenious devices, including copper tubes that when installed in the bats’ ears could be opened and closed, and he came reluctantly to the conclusion that “the ear of the bat serves more efficiently for seeing, or at least for measuring distance, than do its eyes.… Can it then be said that … their ears rather than their eyes serve to direct them in flight? I say only that deaf bats fly badly and hurt themselves against obstacles in the dark and in the light, that blinded bats avoid obstacles in either light or dark.”
What became known as “Spallanzani’s bat problem” resisted solution until 1938. In the meantime, scientific understanding of the physics of sound advanced enough to provide hints about how bats navigated, and after the sinking of the Titanic in 1912 Sir Hiram Maxim, inventor of a machine gun, began an effort to develop a shipboard warning system that would prevent nighttime collisions at sea. Recognizing the possibility that animals might perceive sounds that lay outside the limits of human hearing, Maxim’s imagination settled on bat flight, and he proposed that bats navigated using low-frequency sound inaudible to humans. Because water is a remarkably efficient medium for sound, especially low-frequency sound, he envisioned a shipboard system that emitted low-frequency sound under the water’s surface and received its echoes bouncing off solid objects. The returning echoes would cause bells to ring; the stronger the echo and, therefore, the closer the object, the larger the bell that would ring. A few years later an English physiologist named Hartridge suggested that, rather than using low-frequency sound, bats used high frequencies for nighttime navigation.
Finally, in 1938 an undergraduate biology student at Harvard, Donald R. Griffin, took a cage full of bats to the Harvard physics department, where new research on what was called supersonic sound was going on. Here G. W. Pierce had developed a device for generating and detecting sounds above the range of human hearing. Pierce’s “sonic detector” could also transpose these high frequencies to frequencies within the human hearing range. Amplifying the transposed sounds from the caged bats, Griffin and Pierce were greeted with a sonic maelstrom, and once they separated the bats’ audible chatter from this chaos, they were able to identify short bursts of high-frequency pulses.
Griffin’s discovery of the ultrasound produced by bats established as scientific fact something that we have always intuited: that animal perceptual worlds do not necessarily lie within our own. The tree that falls in their forest might not fall in our forest, which might grow in another universe. Griffin would later famously declare that an animal’s voice is a window on its mind and go on to propose and elaborate on contentious ideas about animal thinking and consciousness at a time when science in general denied the possibility of thought, consciousness, and intention to animals. While Griffin’s progress from voice to thought seems natural, it is important that he started with voice and his account of his bat studies brings home quite clearly that voice is, first and foremost, sound. It is a physical phenomenon, and Griffin, like any other scientist interested in how animals communicate, had to master a highly technical understanding of sound.
After World War II he returned to Harvard as a graduate student to continue his pursuit of the bats’ ultrasonic sound pulses, and he found he suddenly had access to what were state-of-the-art tools in that immediate postwar period. He had Professor Pierce’s “sonic detector,” a long parabolic horn focused on a crystal microphone fitted with vacuum tube amplifiers that caused the ultrasonic sound to be translated to lower frequencies audible to human ears. He had an oscilloscope with a cathode ray tube display, and he had a “very expensive” tape recorder. He used these as he resumed his studies of the bats’ ultrasonic pulses and made detailed measurements of their frequencies and the bats’ timing of them.1
For more than a century, physicists like Griffin’s collaborator G. W. Pierce have been developing increasingly sophisticated techniques to visualize and measure the most fundamental physical attributes of sound, and the evolving technologies can help us understand such perceptual effects of sound as timbre, contour, and rhythm, as well as other physical characteristics of sound. Peacetime adaptation of World War II defense technology and the rapid acceleration of technological advance it spawned made animal voices much more accessible to scientists in all fields. But, not surprisingly, ornithologists got the jump on the others.
At Cornell University, the Laboratory of Ornithology began recording birdsong as soon as the technology became available. Until the early 1920s sound was captured for reproduction by mechanically transferring its vibrations into grooves on an impressionable material and then using a stylus over the grooved material to reproduce the vibrations. In 1929, less than a decade before Griffin recognized the ultrasound of bats, Arthur Allen, ornithologist and founder of the Lab of O, was approached by the Fox-Case Movietone Corporation for help using birds to demonstrate the company’s new technology, the motion picture with synchronized sound. An electromagnetic microphone converted the sound vibrations into electrical signals that were captured on film, and the vibrations were reproduced by reversing that process. Using the company’s equipment, Allen and his colleague Peter Paul Kellogg were able to record the voices of a song sparrow, a house wren, and a rose-breasted grosbeak. The equipment may have been new and for that time fantastically expensive, but it was also big and heavy and yielded a poor product. Even so, Allen and Kellogg were drawn by the potential of electrical sound recording and began to work with the university’s electrical engineering department to develop their own equipment. By the early 1930s they were making expeditions across North America to record the voices and behavior of birds, including the soon-to-be-imperiled ivory-billed woodpecker and the California condor.
At that time the best available recording medium was the nitrocellulose film used for motion pictures. But the film was physically unstable, and when Allen, Kellogg, and Albert Brand undertook a military assignment to record birds in Panama during World War II, the corrosive heat and moisture of the tropics prompted them to adopt direct-to-shellac electrical recording. Vinyl was still a few years away.2
While the recording medium changed periodically—from shellac to vinyl to tape—the processes of electrical recording remained essentially the same until the introduction of digitization and the CD in 1982. In digital recording, the capture of the sound waves by microphone is still “analog,” but the electrical signal from the microphone is stored in a series of binary numbers representing the characteristics of the sound wave. This technological shift has dramatically altered the working lives of scientists who work on animal communication. They can view and manipulate spectrographic images of animal voices on a computer screen, and they can produce digital imitations of these voices for experimental purposes. One interesting extension of digital sound in biological research is the application of digital signal processing to animal voices. This is the same technology that brings you those eerie and irritating automated telephone responses that devour your time as you try to eventually reach the person you intended to call, and a consortium of scientists called the Dr. Dolittle Project is using digital signal processing to automate detailed analysis and classification of animal voices. It can produce such specific analyses that it will allow researchers to identify not only the animal’s species but the individual animal. It could become a valuable conservation tool for monitoring wildlife populations.3
In case you have arrived here without the essentials of sound—as I did—I am laying these out because sound recording and reproduction are the technological heart of the most essential experiment in vocal communication research: the playback study. This type of experiment was devised to solve a fundamental problem that vexes any investigation of animal behavior: animals can’t talk. It has a simple scheme: play a recording of an animal voice to another animal, usually the same kind of animal, and watch what happens. There are more variations of this scheme than there are for “Twinkle, Twinkle, Little Star”—swap the sex of the caller or the listener, change some phrase in the call, alter some perceptual capacity of the listener—and some of them are ingenious work-arounds for this animal-human communications barrier. But the basic design and the need for sound reproduction remain the same. You’ll find this is the case with every animal you hear from in this book, except Spallanzani’s and Griffin’s bats. This is because, as fascinating as the ultrasonic voice of a bat is, it isn’t used for what we usually think of as communication; it is used for navigation. Echolocation is a form of self-communication: the caller and the listener are the same animal.
In spite of technological advances and the increased sophistication in the design of experiments that they allow, we are still, in a number of senses, listening in the dark. There are many voices to which we are physically deaf, like the bat’s ultrasound and the infrasound that elephants use to communicate over distances. When it comes to the voices we can hear, we are in many cases too deafened by the din of our own impossibly noisy world to be able to attend to them—and of course we have polluted the sonic universes of other animals with our own clatter and shriek.
As I begin to look beyond the technical aspects of the sounds of animal voices, two big questions about the bird and the human singer emerge: Why sing? and What does the song mean? The answers to these questions should reveal similarities and differences between the way we humans use our voices and the ways animals use theirs. Why did Sheila Jordan want to sing and what did she want to do as she opened her song? What effects was she aiming for? And what about the mockingbird? I know that science, because of its current emphasis on evolutionary fitness, will link the bird’s singing to his survival or the survival of his family. Is Sheila’s art connected in even the most remote way to her survival or ours? Did life-or-death desperation drive the bird to open his mouth and sing in parody? Just what did the bird think he was doing with that stupid beep? Did he, in fact, think anything at all about the sound he produced or did he just receive and send, receive and send? We don’t yet know the purposes of millions of specific vocal sounds. We don’t know whether specific animal vocalizations are innate or if the animals must learn to make these sounds—and if they learn, how does their education take place?
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Everything I am reading about animals and their voices declares that humans are the sole proprietors of language and music, and nearly everything I read about human vocalizing makes the same claim, often with the slightly defensive proposition that language and music evolved only in humans. The authors seem content to accept that assumption as an always-has-been-always-will-be and to look no further into it. I accept the fact that we humans are singletons blessed with singular capacities. But humans did evolve, and we recognize our biological relations to other animals, including the idea that our brains evolved as did the brains of other animals. I have trouble swallowing claims that we are biologically linked through evolution but features of our brains and thought processes came to us full blown by some other means. Apparently Darwin did too. He was interested in the similarities between the ways animals and humans communicated their emotions and expressed frustration with the prevailing attitudes of his time. In The Expression of the Emotions in Man and Animals, he declared, “No doubt as long as man and all other animals are viewed as independent creations, an effectual stop is put to our natural desire to investigate as far as possible the causes of Expression.”4
When we talk about ourselves in relation to all other animals, we often resort to the word higher, and from a scientific perspective this refers to Darwin’s metaphor for the scheme of evolution, the tree of life. He saw the process as branching upward from the very simplest forms of life into progressively more complex organisms. At the culmination of this process is the human, the conclusion of evolution. In the mid–nineteenth century it took both nerve and humility for Darwin to describe our place in the natural order this way, to place us among the animals. But even though we now have a much richer understanding of evolution, we still rely on Darwin’s metaphor, and this assumption blinds us to the completeness of other animals on the branches beneath us, the self-designated tree-topping angels. It prevents us from seeing the elegance with which they solve the problems of survival and from understanding the parallels between the ways in which animals develop and the ways we do. Parallels, as well as direct links, are important not only because they are the way evolution expresses itself but because they are the sources of powerful insight about ourselves. If we can look at ourselves with Darwin’s humility and accept human life as animal life, it will be apparent that the more we know about animals, the better we will understand our own lives.
It’s a long evolutionary leap from the mockingbird to Sheila Jordan and you and me, and an even longer leap from a less developed vertebrate such as a frog to us. This leap flies over myriad animals that call and sing to find food, arrange for mates, defend themselves—just as my leaps between frogs and deer, and between birds and elephants, skip over hundreds of voices and thousands of sounds. Although many of these sounds are inaudible to us—they are too high or too low for us to hear—we know they occur because they cause changes in behavior. A bat zooms up to snatch an insect, a group of elephants sets out on a long march. The voices we can hear, like those of the mockingbird, the spring peeper frogs, the howl of a wolf, the roar of a lion, and even the sounds of the dog and cat we keep in our living quarters, are for the most part unintelligible to us. But we intuitively understand a central fact about these sounds: voices are social glue. They help animals locate and identify one another. They keep animal societies together in many of the same ways our voices integrate our social life—through flirting, bickering, mating, fighting, and making up.
Animals use their voices to establish their positions in their societies, and although many people don’t seem to understand the connections between society and survival, these are vital to the persistence of many species. For animals that live socially, family and social groups are not just a happy add-on to the animal’s circumstances. They are part of the biological structure of the species. The more intensely social an animal is, the more complex its use of its voice. To advertise for a mate, an isolated male túngara frog sings a whining glissando. In competition with other males, the frog will embellish this vocal sweep with a rudimentary chuck or two. At the other social extreme, the African elephant lives in a well-ordered matriarchy and uses two highly developed systems of vocal communication, the familiar trumpeting audible to humans, which it uses for close-range needs, and infrasound utterances for long-range contact with other family groups.
Each animal, including humans like you and me, lives in its own sound universe. It tunes into those sounds that are critical to its existence and essential to the social life that supports its survival. Each voice, including our own, is perfectly adapted to a particular kind of place in the world and to a society. Head injury or no head injury, hearing loss or no hearing loss, I would be missing many animal voices. So would you, because we have a built-in deafness, the limitations of our perceptual capacity. All of the other animals live with similar limitations, and each animal species occupies a unique world, its environment as perceived and negotiated by that particular animal. A wild turkey and a raccoon, for instance, may share the ground floor of the woodlot on my farm, but they survive because they see the woodlot, smell it, and hear it quite differently. Animal behaviorists call this package of physical and sensory surroundings umwelt, and sound is a powerful, pervasive force in this sensory mix.
The mockingbird and its obsessive mimicry fit in quite comfortably in backyards and, yes, college campuses, where its voice has established a relatively secure livelihood for this bird. But what about Sheila Jordan? Where do she and her survival fit in? At the end of the evolutionary line? She has syllables. She has words and sentences that refer to things that exist only in our minds, which we call ideas. She has music. What Sheila Jordan has is a far cry, as it were, from what any other animal has. Or is it?
Many animals are often credited rather casually with having “language.” But do they really? Are the chirps of a beluga whale mere primitive prototypes of the more complex series of more sophisticated syllables in Sheila’s “I’d like to get you on a slow boat to China,” or are they something more? A good deal of time and effort continue to be spent to identify what features separate our species from the other animals that have not been endowed with language and music. These are truly fascinating projects, but their goal is different from mine. I am interested in how animals’ uses of voice have evolved to meet the challenges of survival and persistence, because any parallels between their vocalizing and ours will deepen our understanding of both. Certainly the speech skills that can be taught to chimpanzees or parrots yield a lot of valuable information about their physical and cognitive capacities, but these aren’t skills that the animals call up when they live in the wild. They have been untapped or perhaps are left over from earlier evolutionary iterations. Somewhere in the gap between animals and humans, music and language evolved. I am interested in the traits that lead up to that gap and whether or not some fragments of those traits emerge on the other side of the gap, that is, in humans.
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These thoughts about animal voices are pressing as my bruised brain forces me to reevaluate my ability to hear and understand. I have been trying to dodge a medical appraisal because I don’t want to admit to any losses, but eventually an incident in a restaurant calls the question about my hearing. I am at dinner with three friends from the horse world, all a little younger than me. Our table backs up on the bar, where the noises of the television and glassware and the conversations competing with them bounce between a long mirror and the opposite wall. I am saying something earnest about a horse, and my friends begin to laugh at me because they have long since left the topic of horses and are announcing their dinner decisions. I have just blundered into this conversation and spoken nonsense. I cringe, and the next day I make an appointment with a specialist.
The audiologist puts me through an intensive battery of hearing and balance tests. These are exhausting and take the better part of a day, and they don’t reveal much. “You have some loss. High end, and it’s not too bad now, nothing out of the ordinary for someone your age. But you’ll probably lose more.” I can expect to hear, but not everything. I can still take pleasure in music and in the rackety traffic of everyday conversation, but these perceptions are likely to fade.
Eventually, in the spring of 2008, after nearly three years of dizziness, I escape the fun house and move away from that woozy building. I have gradually recovered my balance, and I stop reading and put down my books to look outside to the natural world. It is time to go out there, while my hearing is still serviceable, to listen and to look into the questions that have been on my mind—Why sing? What does the song do? And what does the song mean? In order to be able to make sense of animal voices I need to hear them as they actually occur. It’s time to get the show—compromised hearing and all—on the road.
It turns out that my timing is good. Not only are there some adventuresome field and lab studies under way, but also the role of evolution in human language and music—which was largely ignored and even explicitly denied until only about ten years ago—has become the subject of lively scientific speculation. Eventually this speculation may lead to some understanding of what actually happened in the gap between animals and humans.
I begin prospecting. The first person I call is Eugene S. Morton, an ornithologist recently retired from the Smithsonian Institution and whose book with Donald H. Owings on animal vocal communication gave me a good grounding.5 Gene is an old Panama hand, and he has published on all kinds of birds, common and rare, and, just as important, on theories of vocal communication. He is very generous with his ideas and his contacts. As I begin to get in touch with scientists who work on vocal communication, I am aware that their current research, the projects in which they are most keenly interested, are works-in-progress. They may have only begun an investigation or they may be approaching some conclusions. In either case, I will be able to take away only a snapshot of the moment. I’ll have to define the most compelling questions and figure things out from there.
Gene sends me to the young behavioral ecologist David Logue, among others. I have a lengthy discussion with David about his research on a bird that lives in the Neotropics, the black-bellied wren, and about what he sees as up-and-coming research trends. Of course, I want to see and hear this wren in real time and learn how David figured out what he knows. But I am aware that birds sing in complicated exchanges in a hard-to-reach realm, and what I want to do first is understand the most basic transactions set off by animal voices. So I tell David I would like to start with a simple, or relatively simple, animal, and he suggests that I contact Mike Ryan, who has been listening to the same frog and its communication system for decades.
When I phone Mike Ryan, I reach him in his lab at the University of Texas in Austin, and as is typical, he is very busy there, or writing something when he’s not in the lab. But, as is also typical, he is willing to share his work with me. I go down to Austin to spend two days in Mike’s lab. Happily, I am ignorant of his status in the field of animal behavior—he is a honcho, though too modest to make anyone aware of this—because otherwise I would have been uneasy about asking for so much of his time in Austin and I might not have invited myself down to his research site in the Panama Canal Zone. But I do, and two months later, I arrive in the dank hamlet of Gamboa, an outpost of the Smithsonian Tropical Research Institute.


 
Copyright © 2012 by Holly Menino