Can Prairie Dogs Talk?

Con Slobodchikoff and I approached the mountain meadow slowly, obliquely, softening our footfalls and conversing in whispers. It didn’t make much difference. Once we were within 50 feet of the clearing’s edge, the alarm sounded: short, shrill notes in rapid sequence, like rounds of sonic bullets.

We had just trespassed on a prairie-dog colony. A North American analogue to Africa’s meerkat, the prairie dog is trepidation incarnate. It lives in subterranean societies of neighboring burrows, surfacing to forage during the day and rarely venturing more than a few hundred feet from the center of town. The moment it detects a hawk, coyote, human or any other threat, it cries out to alert the cohort and takes appropriate evasive action. A prairie dog’s voice has about as much acoustic appeal as a chew toy. French explorers called the rodents petits chiens because they thought they sounded like incessantly yippy versions of their pets back home.

On this searing summer morning, Slobodchikoff had taken us to a tract of well-trodden wilderness on the grounds of the Museum of Northern Arizona in Flagstaff. Distressed squeaks flew from the grass, but the vegetation itself remained still; most of the prairie dogs had retreated underground. We continued along a dirt path bisecting the meadow, startling a prairie dog that was peering out of a burrow to our immediate right. It chirped at us a few times, then stared silently.

“Hello,” Slobodchikoff said, stooping a bit. A stout bald man with a scraggly white beard and wine-dark lips, Slobodchikoff speaks with a gentler and more lilting voice than you might expect. “Hi, guy. What do you think? Are we worth calling about? Hmm?”

Slobodchikoff, an emeritus professor of biology at Northern Arizona University, has been analyzing the sounds of prairie dogs for more than 30 years. Not long after he started, he learned that prairie dogs had distinct alarm calls for different predators. Around the same time, separate researchers found that a few other species had similar vocabularies of danger. What Slobodchikoff claimed to discover in the following decades, however, was extraordinary: Beyond identifying the type of predator, prairie-dog calls also specified its size, shape, color and speed; the animals could even combine the structural elements of their calls in novel ways to describe something they had never seen before. No scientist had ever put forward such a thorough guide to the native tongue of a wild species or discovered one so intricate. Prairie-dog communication is so complex, Slobodchikoff says — so expressive and rich in information — that it constitutes nothing less than language.

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That would be an audacious claim to make about even the most overtly intelligent species — say, a chimpanzee or a dolphin — let alone some kind of dirt hamster with a brain that barely weighs more than a grape. The majority of linguists and animal-communication experts maintain that language is restricted to a single species: ourselves. Perhaps because it is so ostensibly entwined with thought, with consciousness and our sense of self, language is the last bastion encircling human exceptionalism. To concede that we share language with other species is to finally and fully admit that we are different from other animals only in degrees not in kind. In many people’s minds, language is the “cardinal distinction between man and animal, a sheerly dividing line as abrupt and immovable as a cliff,” as Tom Wolfe argues in his book “The Kingdom of Speech,” published last year.

Slobodchikoff thinks that dividing line is an illusion. To him, the idea that a human might have a two-way conversation with another species, even a humble prairie dog, is not a pretense; it’s an inevitability. And the notion that animals of all kinds routinely engage in sophisticated discourse with one another — that the world’s ecosystems reverberate with elaborate animal idioms just waiting to be translated — is not Doctor Dolittle-inspired nonsense; it is fact.

Like “life” and “consciousness,” “language” is one of those words whose frequent and casual use papers over an epistemological chasm: No one really knows what language is or how it originated. At the center of this conundrum is a much-pondered question about the relationship between language and cognition more generally. Namely, did the mind create language or did language create the mind? Throughout history, philosophers, linguists and scientists have argued eloquently for each possibility. Some have contended that thought and conscious experience necessarily predate language and that language evolved later, as a way to share thoughts. Others have declared that language is the very marrow of consciousness, that the latter requires the former as a foundation.

In lieu of a precise definition for language, many experts and textbooks fall back on the work of the American linguist Charles Hockett, who in the 1950s and ’60s proposed a set of more than a dozen “design features” that characterize language, like semanticity — distinct sounds and symbols with specific meanings — and displacement, the ability to speak of things outside your immediate environment. He acknowledged that numerous animal-communication systems had at least some of these features but maintained that only human language boasted them all. For those who think that language is a prerequisite for consciousness, the unavoidable conclusion is that animals possess neither.

To many biologists and neuroscientists, however, this notion smacks of anthropocentrism. There is now a consensus that numerous species, including birds and mammals, as well as octopuses and honeybees, have some degree of consciousness, that is, a subjective experience of the world — they feel, think, remember, plan and in some cases possess a sense of self. In parallel, although few scientists are as ready as Slobodchikoff to proclaim the existence of nonhuman language, the idea that many species have language-like abilities, that animal communication is vastly more sophisticated than Hockett and his peers realized, is gaining credence. “It’s increasingly obvious just how much information is encoded in animal calls,” says Holly Root-Gutteridge, a bioacoustician at the University of Sussex. “There’s now a preponderance of evidence.”

In the 1990s, inspired in part by Slobodchikoff’s studies, the primatologist Klaus Zuberbühler began investigating monkey vocalizations in the dense and cacophonous forests of the Ivory Coast in Africa. Over the years, he and his colleagues discovered that adult male Campbell’s monkeys change the meaning of their screeches by combining distinct calls in specific sequences, adding or omitting an “oo” suffix. Krak exclusively warns of a leopard, but krak-oo is a generalized alarm call; isolated pairs of booms are a “Come this way!” command, but booms preceding krak-oos denote falling tree branches. Studies of songbirds have also uncovered similar complexity in their communication. Japanese great tits, for example, tell one another to scan for danger using one string of chirps and a different set of notes to encourage others to move closer to the caller. When researchers played the warning followed by the invitation, the birds combined the commands, approaching the speaker only after cautiously surveying the area. In the South Pacific, biologists have shown that humpback-whale songs are neither random nor innate: rather, migrating pods of humpback whales learn one another’s songs, which evolve over time and spread through the ocean in waves of “cultural revolution.” And baby bottlenose dolphins develop “signature whistles” that serve as their names in a kind of roll call among kin.

With the help of human tutors, some captive animals have developed especially impressive linguistic prowess. Dolphins have learned to mimic computer-generated whistles and use them as labels for objects like hoops and balls. A bonobo known as Kanzi communicates with a touch-screen displaying hundreds of lexigrams, occasionally combining the symbols with hand gestures to form simple phrases. And over the course of a 30-year research project, an African gray parrot named Alex learned to identify seven colors, five shapes, quantities up to eight and more than 50 objects; he could correctly pick out the number of, for instance, green wooden blocks on a tray with more than a dozen objects; he routinely said “no,” “come here” and “wanna go X” to get what he desired; and on occasion he spontaneously combined words from his growing vocabulary into descriptive phrases, like “yummy bread” for cake.

Slobodchikoff’s studies on prairie dogs have long hovered on the periphery of this burgeoning field. Unknown to Slobodchikoff, around the same time that he began recording prairie-dog alarm calls in Flagstaff, Peter Marler, the renowned animal-communication expert and one of Slobodchikoff’s former professors, was working on a similar study, one that would eventually redefine the field. In the spring of 1977, Marler sent Robert Seyfarth and Dorothy Cheney — a young husband-and-wife duo of primate scientists — to Amboseli, Kenya, to study the alarm calls of small silver-haired monkeys known as vervets. Earlier research had hinted that vervet monkeys produced different vocal warnings for different predators: a kind of bark to warn of a leopard; a low-pitched staccato rraup for a martial eagle; and a high-pitched chutter for a python. Seyfarth and Cheney decided to further investigate these findings in a controlled field experiment.

The two scientists hid a loudspeaker in the bushes near different groups of vervets and played recordings of their alarm calls, documenting the monkeys’ responses. Even in the absence of actual predators, the recordings evoked the appropriate escape strategies. Leopard-alarm calls sent monkeys scampering into the trees. When they heard eagle-alarm calls, they looked up and took cover in the bushes. In response to the warning for snakes, the primates reared up on their hind legs and scanned the ground. Contrary to the consensus of the time, the researchers argued that the sounds animals made were not always involuntary expressions of physiological states, like pain, hunger or excitement. Instead, some animals systematically used sounds as symbols. In both academia and the popular press, vervet monkeys became celebrated mascots for the language-like abilities of animals.

While the vervet research won acclaim, Slobodchikoff’s remained frustratingly sidelined. Marler, Seyfarth and Cheney worked for the well-staffed and moneyed Rockefeller University in New York; Slobodchikoff conducted his studies on a shoestring budget, compiling funds from the university’s biology department, very occasional grants and his own bank account. Slobodchikoff did not collect enough data to formally present his research at a conference until 1986. And it was not until 2006 that he published a study with the same kind of playback techniques that Cheney and Seyfarth used in Kenya, which are essential to demonstrating that an animal comprehends and exploits the variation in its calls. Although many scientists attended Slobodchikoff’s talks at conferences and spoke with him about his research in private, they rarely referenced his studies when publishing their own. And despite a few news stories and nature documentaries, prairie dogs have not secured a seat in public consciousness as a cognitively interesting species.

It did not take long for Slobodchikoff to master the basic vocabulary of Flagstaff’s native prairie dogs. Prairie-dog alarm calls are the vocal equivalent of wartime telegrams: concise, abrupt, stripped to essentials. On a typical research day, Slobodchikoff and three or four graduate students or local volunteers visited one of six prairie-dog colonies they had selected for observation in and around Flagstaff. They usually arrived in the predawn hours, before the creatures emerged from their slumber, and climbed into one of the observation towers they had constructed on the colonies: stilted plywood platforms 10 feet high, covered by tarps or burlap sacks with small openings for microphones and cameras. By waiting, watching and recording, Slobodchikoff soon learned to discriminate between “Hawk!” “Human!” and so on — a talent that he says anyone can develop with practice. And when he mapped out his recordings as sonograms, he could see clear distinctions in wavelength and amplitude among the different calls.

He also discovered consistent variations in how prairie dogs use their alarm calls to evade predators. When a human appeared, the first prairie dog to spot the intruder gave a sequence of barks, which sent a majority of clan members scurrying underground. When a hawk swooped into view, one or a few prairies dogs each gave a single bark and any animal in the flight path raced back to the burrow. (Slobodchikoff suspects that, because of a hawk’s speed, there’s little time for a more complex call.) The presence of a coyote inspired a chorus of alarm calls throughout the colony as prairie dogs ran to the lips of their burrows and waited to see what the canine would do next. When confronted with a domestic dog, however, prairie dogs stood upright wherever they were, squeaking and watching, presumably because tame, leashed dogs were generally, though not always, harmless.

Something in Slobodchikoff’s data troubled him, however. There was too much variation in the acoustic structure of alarm calls, much more than would be expected if their only purpose was to distinguish between types of predator. Slobodchikoff arranged for various dogs — a husky, a golden retriever, a Dalmatian and a cocker spaniel — to wander through a prairie-dog colony one at a time. The recorded alarm calls were still highly variable, even though the intruders all belonged to the same predator class. “That led me to think, What if they are actually describing physical features?” Slobodchikoff remembers. What if, instead of barking out nouns, prairie dogs were forming something closer to descriptive phrases?

To find out, he became a participant in his own experiment. Slobodchikoff and three colleagues paraded through two prairie-dog colonies dressed in either jeans and white lab coats, or jeans and variously colored shirts: blue, gray, orange, green. The prairie dogs produced highly similar alarm calls for each person in the lab coat, except for one especially short researcher. But they chirped in very different ways for most of the different colored shirts. In a related experiment, three slender women differing in height by just a bit meandered through a prairie-dog habitat dressed identically except for the color of their T-shirts. Again the animals varied their calls. And in another study, prairie dogs changed the rate of their chirping to reflect the speed of an approaching human.

If prairie dogs had sounds for color and speed, Slobodchikoff wondered, what else could they articulate? This time, he and his colleagues designed a more elaborate test. First they built plywood silhouettes of a coyote and a skunk, as well as a plywood oval (to confront the prairie dogs with something foreign), and painted the three shapes black. Then they strung a nylon cord between a tree and an observation tower, attached the plywood figures to slotted wheels on the cord and pulled them across the colony like pieces of laundry. Despite their lack of familiarity with these props, the prairie dogs did not respond to the cutouts with a single generalized “unknown threat” call. Rather, their warnings differed depending on the attributes of the object. They unanimously produced one alarm call for the coyote silhouette; a distinct warning for the skunk; and a third, entirely novel call for the oval. And in a follow-up study, prairie dogs consistently barked in distinct ways at small and large cardboard squares strung above the colony. Instead of relying on a fixed repertory of alarm calls, they were modifying their exclamations in the moment to create something new — a hallmark of language Hockett called “productivity.”


Bag-like sea creature was humans’ oldest known ancestor

January 30, 2017
Bag-like sea creature was humans' oldest known ancestor
Artist’s reconstruction of Saccorhytus coronarius, based on the original fossil finds. The actual creature was probably no more than a millimeter in size. Credit: S Conway Morris / Jian Han

Researchers have identified traces of what they believe is the earliest known prehistoric ancestor of humans—a microscopic, bag-like sea creature, which lived about 540 million years ago.

Named Saccorhytus, after the sack-like features created by its elliptical body and large mouth, the species is new to science and was identified from microfossils found in China. It is thought to be the most primitive example of a so-called “deuterostome”—a broad biological category that encompasses a number of sub-groups, including the vertebrates.

If the conclusions of the study, published in the journal Nature, are correct, then Saccorhytus was the of a huge range of species, and the earliest step yet discovered on the evolutionary path that eventually led to humans, hundreds of millions of years later.

Modern humans are, however, unlikely to perceive much by way of a family resemblance. Saccorhytus was about a millimetre in size, and probably lived between grains of sand on the seabed. Its features were spectacularly preserved in the fossil record—and intriguingly, the researchers were unable to find any evidence that the animal had an anus.

The study was carried out by an international team of academics, including researchers from the University of Cambridge in the UK and Northwest University in Xi’an China, with support from other colleagues at institutions in China and Germany.

Simon Conway Morris, Professor of Evolutionary Palaeobiology and a Fellow of St John’s College, University of Cambridge, said: “We think that as an early deuterostome this may represent the primitive beginnings of a very diverse range of species, including ourselves. To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail is jaw-dropping. All deuterostomes had a common ancestor, and we think that is what we are looking at here.”

Degan Shu, from Northwest University, added: “Our team has notched up some important discoveries in the past, including the earliest fish and a remarkable variety of other early deuterostomes. Saccorhytus now gives us remarkable insights into the very first stages of the evolution of a group that led to the fish, and ultimately, to us.”

Most other early deuterostome groups are from about 510 to 520 million years ago, when they had already begun to diversify into not just the vertebrates, but the sea squirts, echinoderms (animals such as starfish and sea urchins) and hemichordates (a group including things like acorn worms). This level of diversity has made it extremely difficult to work out what an earlier, common ancestor might have looked like.

The Saccorhytus microfossils were found in Shaanxi Province, in central China, and pre-date all other known deuterostomes. By isolating the fossils from the surrounding rock, and then studying them both under an electron microscope and using a CT scan, the team were able to build up a picture of how Saccorhytus might have looked and lived. This revealed features and characteristics consistent with current assumptions about primitive deuterostomes.

Dr Jian Han, of Northwest University, said: “We had to process enormous volumes of limestone – about three tonnes – to get to the fossils, but a steady stream of new finds allowed us to tackle some key questions: was this a very early echinoderm, or something even more primitive? The latter now seems to be the correct answer.”

In the early Cambrian period, the region would have been a shallow sea. Saccorhytus was so small that it probably lived in between individual grains of sediment on the sea bed.

The study suggests that its body was bilaterally symmetrical—a characteristic inherited by many of its descendants, including humans—and was covered with a thin, relatively flexible skin. This in turn suggests that it had some sort of musculature, leading the researchers to conclude that it could have made contractile movements, and got around by wriggling.

Perhaps its most striking feature, however, was its rather primitive means of eating food and then dispensing with the resulting waste. Saccorhytus had a large mouth, relative to the rest of its body, and probably ate by engulfing food particles, or even other creatures.

A very distant relative
A very distant relative

A crucial observation are small conical structures on its body. These may have allowed the water that it swallowed to escape and so were perhaps the evolutionary precursor of the gills we now see in fish. But the researchers were unable to find any evidence that the creature had an anus. “If that was the case, then any waste material would simply have been taken out back through the mouth, which from our perspective sounds rather unappealing,” Conway Morris said.

The findings also provide evidence in support of a theory explaining the long-standing mismatch between fossil evidence of prehistoric life, and the record provided by biomolecular data, known as the “molecular clock”.

Technically, it is possible to estimate roughly when species diverged by looking at differences in their genetic information. In principle, the longer two groups have evolved separately, the greater the biomolecular difference between them should be, and there are reasons to think this process is more or less clock-like.

Unfortunately, before a point corresponding roughly to the time at which Saccorhytus was wriggling in the mud, there are scarcely any fossils available to match the molecular clock’s predictions. Some researchers have theorised that this is because before a certain point, many of the creatures they are searching for were simply too small to leave much of a fossil record. The microscopic scale of Saccorhytus, combined with the fact that it is probably the most primitive deuterostome yet discovered, appears to back this up.

The Gravest Problem Animals Face: Man’s Self-Appointed Supremacy Over Them


“Time is running out” (A final message from John A. Livingston)

The following thoughts appear in the last chapter of the late John A. Livingston’s 1973 book, One Cosmic Instant; Man’s Fleeting Supremacy (a book I can especially relate to in that it dissects and begins to dismantle the entrenched, arrogant attitude that humans are apart from, and even superior to, the rest of life here on Earth). Livingston begins by comparing this complex, arrogant, human attitude to an ecosystem:

“In their natural environment, living beings face an infinity of survival problems—food shortages, predators, diseases, competitors, population stresses, and so on. The gravest problem they now face, however—man’s self-appointed supremacy over them—is strangely like an ecosystem. It has a vast and complicated array of interlocking components…

“As any naturalist knows, the quickest and neatest way to destroy an eco-system is to simplify it, to reduce its complexity and thus short-circuit the equilibrium maintained by the mutual interdependence of its component parts. Perhaps the traditional, cultural, institutional, conceptual eco-construct can be decomplexified by our deliberate manipulation—by the exercise of our conscious choice. Intervention in its workings will require degrees of courage, sacrifice, imagination and generosity which have not frequently been displayed in the course of man’s relationship with his environment. One hesitates to predict whether we will be willing to undertake it. The destruction of the power hierarchy over nature will require a shift in attitudes more profound than we can presently imagine.

“The process of simplification or decomplexification will be drastic. Suppose one were to elect to have an initial go at the “rights of man”—the God-given rights of man the individual and man the species. Suppose it were feasible to actually remove some of those rights, one after the other. The consequences might be astonishing… Environmental forces are already ‘eroding’ traditional rights.

“Then there is the right to have children. Suppose people were no longer permitted to reproduce beyond the replacement level. Replacement level means one adult, one child—zero population growth…The environmentalist must look hard at traditional human freedoms.

“There are other ‘rights’ such as the imagined right of man to kill non-human animals for amusement. Clearly the environment itself will deal with this tradition, simply as the effect of men having joyfully massacred so many ducks, geese, rhinos, elephants and Cape buffaloes that there will not be enough of them to go round. A similar end will come to the fashion industry’s apparent determination to exploit to the bitter end the final stocks of leopard, tiger, jaguar, and the rest.

“What of the more fundamental, unquestioned rights of man the species? The right to populate at will must certainly be removed, either by our own conscious choice or by a natural backlash on the part of the biosphere itself. The right to dominate animals of other species, and to dominate landscapes, will not be subverted as readily. Other beings, as species and as landscapes, do not have the ‘clout’ of the combined forces of the biosphere. But that right, too, will disappear. It will be a sad process, for we will not give up the right to dominate without a struggle—a struggle which will cost both human and non-human nature exorbitantly.

“It will not be in our best interests to allow the environment to dismantle our conceptual power structure for us. In such an eventuality, cosmic forces would make life devastating. We should not expect the environmental counter attack to be nearly so dramatic or spectacular as the ancient vision of the Apocalypse, but it would be equally disastrous. Because it would not be sudden, it would be even more agonizing…

“Time is running out for the dismantling of the institutions which have kept us so grimly locked in step with ‘progress.’ There is even less time for reflection on the merits of the traditional components of our culture which have brought us—and all of nature—to the present point of departure. A point of departure it is, either from the narrow and egocentric culture course we have adopted, or premature departure from the blue planet itself. If we are not capable of identifying the specific threads in the fabric of our beliefs which have sustained the entire tapestry upon which the myth of human dominance is emblazoned, then it may be too late already.

“The hope for survival of non-human nature is dim. There is a familiar scenario. As conditions worsen for human populations—as they will, initially, in underprivileged parts of the world—every ounce and erg of our most refined technological skills and energies will be brought into play to extract from Earth and its non-human inhabitants the basic ingredients for human survival. We will first destroy all of the larger animals, either for meat or because they compete with us for space, together with those which may be intolerant of our activities because of their specific natural specializations. Extinctions of non-human species, without replacement, will continue at an accelerating rate, until the only non-human beings remaining will be those who are willing to share their squalor with us—rats, gutter curs, and parasites and micro-organisms which thrive in time environmental dislocation.

“Our capacity for seeing into the future—and we do not want to know about futures of that kind. We withdraw behind the opaqueness of closed imaginations and familiar fancies. We acknowledge that, yes, the situation is bad, but human ingenuity, creativity, enterprise and good will overcome all difficulties.

“While we should be unravelling the threads of tradition, we are weaving ever more elaborate curtains of rationalization. Every avenue of questioning closed off is another route to intellectual and spiritual freedom barricaded forever.

“There is no engineering answer to a problem created by culture. The worst in humanistic ways of thinking opened and kept open the conceptual man/nature dichotomy, and only mature wisdom and insight that categorize the best in natural philosophic tradition can mend it.”