A small tasty animal like a rabbit is well served by learning the alarm calls of as many other species as possible. But the rabbit has no need to produce many alarm calls. It needs to be able to thump its feet in warning to other rabbits and, apparently, it also needs to be able to scream in desperation when actually in the grip of a predator. Just why rabbits have the ability to utter a last-ditch scream has been debated—surely it’s useless to cry for help if the only individuals likely to care about your well-being are also rabbits. On the other hand, what has the rabbit got to lose? Another predator might show up to see what’s happening and the rabbit might get away in an ensuing confrontation. Predators are so interested in rabbit screams that hunters regularly use “rabbit calls” to attract them. So a rabbit may have a greater need to understand vocal communication than to vocalize.
I signed it with an X
A social animal might wish to identify itself to others of its group. That dolphins have “signature whistles,” calls that are unique to individuals, was first suggested in 1965 by M. C. and D. K. Caldwell, but the discovery “languished” during a period when some frenzied dolphin admirers held out for the idea that dolphins might have a language fully as sophisticated as—perhaps more sophisticated than—our own, which would shortly be revealed to us. Not that anyone’s bitter about Flipper and John Lilly and “floating hobbits” and the notion of ambassadors who carry a message to humanity from the divine. Not really bitter.
There is still controversy about signature whistles, with Brenda McCowan and Diana Reiss, for example, arguing that dolphins merely have individual vocal variations of shared contact calls, perhaps with regional dialectical differences. “These differing results from different methods of categorization can be resolved only by testing how dolphins themselves perceive whistles,” writes Peter Tyack, whose research supports the signature whistle hypothesis. Tests with captive and wild dolphins show that they clearly recognize each other’s whistles—are they recognizing a signature or merely a voice?
What good would a signature whistle do? Why would a dolphin benefit by saying “Hi, it’s Bob,” when he could just say “Hi” and have other dolphins know it’s Bob because they recognize Bob’s voice? Unlike land animals, dolphins vocalize at different water depths, which subject them to different pressures, which change their voices. So Bob the dolphin saying “Hi” when he’s at the surface may sound different from Bob saying “Hi” 20 feet below the surface. But if his whistle structure says “Hi, it’s Bob,” then depth differences won’t matter.
The observations of Janik and Slater, who recorded vocal interactions between wild dolphins in Moray Firth, Scotland, support the idea that wild dolphins—or some wild dolphins—use signature whistles. The dolphins frequently responded to a whistle with “whistle matching”—uttering a whistle of the same kind. The kind of whistles that were matched resembled the signature whistles of captive dolphins.
Baby dolphins aren’t born with apparent signature whistles. Of the dolphins of Monkey Mia on the western Australian coast, Rachel Smolker writes, “They make gurgly, irregular, messy-sounding whistles at first. Gradually they refine their sound into a clean, unique whistle by the time they are about six months to a year old.”
Researchers looking for signature whistles in some male dolphins at Monkey Mia in the mid-1900s weren’t finding them. Babies had them, males didn’t seem to. (If it were to turn out that dolphins in some areas have signature whistles and in other areas don’t, that would be a fascinating cultural difference.) But they noticed that three males who swam together, Snubnose, Bibi, and Sicklefin, were uttering more of a whistle called the upcurl. “If the most common whistle a dolphin produced was its signature, then Snubnose, Bibi, and Sicklefin had all converged on the upcurl as their shared signature whistle.” Records showed that these three males had formed an alliance after the period of first recording. They started doing more and more upcurls, and the upcurls sounded more alike. Perhaps they just liked it, or perhaps they were presenting a united front.
Signature thumps
There is no indication that banner-tailed kangaroo rats are capable of vocal learning, yet they too seem to have signatures. Kangaroo rats defend valuable territories consisting of mounds of dirt which the rats use as silos for seeds. These contain tunnels and galleries excavated by generations of kangaroo rats. A kangaroo rat announces its claim to one of these mansions by drumming its feet, making a sound that travels through the air and the ground. (There’s also foot drumming to warn of snakes, but that’s a different pattern.)
A kangaroo rat assembles foot drums into bursts called foot rolls, and assembles foot drums and foot rolls into a foot-drumming signature. Each individual’s signature is consistent, and may stay the same over years, but it can also change. The reason to change your signature is to make sure that it can’t be confused with those of your neighbors. Analysis of the foot-drumming signatures of kangaroo rats near Portal, Arizona, shows that signatures don’t overlap with those of a given kangaroo rat’s neighbors but may overlap with those of kangaroo rats who live farther away.
Kangaroo rats change territories from time to time, for reasons that are mysterious to us. When you move, you get different neighbors, and if you’re a kangaroo rat, you may need to change your signature. During six years of study the kangaroo rat that changed her signature most often was a restless individual who moved four times in a year.
Primates
Compared to birds, all the primates except us seem to be vocal duds. They use innate calls and modify them surprisingly little through learning. Six infant squirrel monkeys were raised in isolated mother-child pairs. Four of the pairs were vocally normal. In the fifth pair, the infant was congenitally deaf. In the sixth pair, the infant was normal, but the mother, due to surgery on her vocal cords, could not make squirrel monkey calls. She could only groan. Researchers examined the calls of all the young monkeys as they grew. Each one made all the calls that squirrel monkeys make, and each did them perfectly.
Adult male orangutans avoid each other. Biruté Galdikas says that if they meet, there are only two possible results: one runs away, or they fight. But it rarely comes to that, because adult males utter ringing “long calls,” and they use these to stay apart. These long calls may need to have no particular content, since to hear one is to understand, “There’s a great big ape over there and he doesn’t care who knows it.”
Gorillas are famous for beating their chests, and some think that chest beating has a communicatory function. You can hear it a mile away, and one chest-beating gorilla is sometimes answered by another. Whether they are saying anything more complex than “Hey, you’re not the only one with a chest” is not known.
Drumming
Primates make nonvocal sound signals at times. Male chimpanzees often drum briefly on the buttresses of forest trees, sometimes uttering pant-hoots as they do. The drumming can be heard at least a kilometer away. This clearly conveys information to other chimpanzees, but it’s unclear how sophisticated the information is. In a 1991 paper, Christophe Boesch analyzed the drumming and subsequent actions of chimpanzees in the Taï Forest of Ivory Coast in the 1980s. This was a community of about 80 chimpanzees, which broke into smaller groups that foraged separately. Often they moved through the forest silently, but at other times the males pant-hooted and drummed loudly on trees with hands and feet.
Christophe Boesch and Hedwige Boesch began to suspect that the drumming conveyed not only information about where the drumming chimp was, but also what he planned to do next, “because we tended to lose contact with them just after drumming was heard. It seemed that the whole chimpanzee community abruptly and often silently changed direction following an outburst of drumming.”
Boesch learned to differentiate the pant-hoots of the different males in the study area, and concluded that the chimpanzees only changed their direction of travel after the highest-ranking male, Brutus, drummed.
Boesch’s analysis identified three kind
s of messages sent by Brutus’s drumming. By drumming first on one tree and then, within two minutes, on another tree a little distance away, Brutus identified a direction of travel. Chimpanzees hearing it would know it was Brutus and they would know what direction his group was going.
If Brutus drummed in two separate bouts on the same tree, Boesch suggests, he indicated that he was planning to rest in that place. When this happened, other chimps were also apt to stop and rest, usually for about an hour.
Lastly, Boesch argued, when Brutus drummed once on one tree and then twice in succession on another tree, or twice on one tree and then once on a second, he “proposed both a change of direction and an hour’s rest.” This was recorded six times. Once Brutus drummed four times on the same tree and everybody rested for two hours, making Boesch wonder if there was a connection between the many drummings and the long rest, but this was observed only once.
Excited by these findings, and now able to identify most of the adult males by voice, Boesch was preparing to gather more data, when, in February 1984, four out of ten adult males vanished, apparently killed by poachers. Within three months, Brutus “stopped sending information to the other community members.”
For Brutus’s messages to be useful, the other chimpanzees needed to understand them. The fact that on one occasion a group of younger chimpanzees ignored one of Brutus’s messages that seemed to indicate an hour’s rest, kept moving, and ended up out of hearing range of the rest of the community, a rare event at that time of year, suggests the possibility that these younger animals either hadn’t learned to understand such messages or didn’t realize the importance of staying in touch.
Chimpanzees need to stay in touch, Boesch writes, so they can join in defense against predators and neighboring chimpanzee groups. In the Taï Forest leopards frequently attacked chimpanzees. In areas such as the Gombe preserve, where chimpanzees have not been recorded communicating this way, there is less predation and better visibility.
Of drumming bouts, anthropologist Adam Clark Arcadi argues that “there is no way to eliminate the possibility that listeners simply deduced the drummer’s current or future position, joined him, and then matched his behavior,” as opposed to the drummer encoding information that was then decoded by the listening apes.
Branch dragging
Primatologist Ellen Ingmanson describes branch dragging, a behavior of wild bonobos in Zaire, which seems to signal two things: the message “Let’s go” and information about the direction the bonobo proposes to take. In a resting group, one of the males will rise, break off a branch, and drag it noisily into the forest for 20 to 30 meters. He repeats this several times, and if all goes well, the others get to their feet and the group proceeds in the direction in which he was dragging the branch. Sometimes another male has a different idea and starts branch dragging in another direction. How the group decides is unclear. The directions were clear enough that Ingmanson could usually predict where the bonobos would go. Occasionally they branch-dragged when a party was in transit, perhaps to lobby for a change of direction or to goad slowpokes.
One October morning, Ingmanson started ape watching early, while the bonobos were still in their nests. Mon came down from his nest and sat, looking between a tree with another bonobo nest and a fruiting tree. Then he snapped a sapling and started branch dragging between the two trees. After ten minutes, Ika looked over the edge of the other nest. “Mon stopped branch-dragging, gave a few excited squeaks and bounces, and looked up at Ika.” But Ika didn’t feel like getting up, and pulled back his head. Mon resumed branch-dragging until Ika put his head out again and then slowly came down. Mon stopped branch-dragging, and the minute Ika hit the ground Mon ran to the fruit tree, slowly followed by Ika.* “Mon had succeeded in getting a friend to join him for breakfast.”
Clever, clever, clever Hans
From time to time, people have tired of trying to understand animals and tried instead to make the animals do the work to communicate with us. The results have been mixed. When professors of animal behavior want to scare their students sober, they tell them the story of Clever Hans. With slides. In the early 1900s Wilhelm von Osten, who thought animals must be smarter than people said, tried to teach simple math to a cat, who did not cooperate. He tried to teach a bear, whose attitude was very bad. He tried to teach a horse, Hans, who was patient and willing. Von Osten, with abacus and blackboard, would pose math questions to Hans, who was supposed to tap his hoof four times if the answer was 4 and so forth. Hans, a brown horse with a white star on his forehead, got pretty good at this, and at shaking his head, and pointing with his head, and at picking up one of several colored cloths. He answered questions regarding square roots correctly and did well when von Osten branched out into questions about the German language.
Von Osten announced the feats of Kluge Hans—Clever Hans—to the world and people flocked to see. Everyone was extremely impressed with the questions Hans could answer, which could be asked by anyone.
Then psychologist Oskar Pfungst performed experiments showing that Hans could only answer questions correctly if he could see someone who knew the answer, ideally von Osten. Hans determined when to stop tapping his hoof, not by noting that 4 is the square root of 16, but by noticing that on his fourth tap von Osten, who had been leaning forward slightly, looking at Hans’s hoof, now straightened slightly, anticipating the end of the tapping. Hans also paid attention when von Osten raised his eyebrows or flared his nostrils minutely.
Von Osten had sincerely believed that in Hans he had created an equine mathematician and was devastated to find that he had merely created a brilliant observer of human physiology. The prevailing reaction of animal behaviorists to Hans’s story is horror at the thought of being fooled that way.
Horses are good at responding to small cues, which is one reason a 60-pound child can steer a 1,000-pound horse at top speed around a course of barrels. From Hans’s point of view, he simply did what he was asked.
Repeat after me: “Puh.”
Hans was at least spared the demand that he speak German, but apes have been subjected to training programs intended to get them speaking English. Keith and Cathy Hayes hoped that if they raised an infant chimpanzee as they would raise an infant human, she would learn to talk just as children do. Although she was a smart and loving little ape, she learned only four words, Mama, Papa, cup, and up, and only after intensive training for six years. The chimpanzee vocal tract is not well shaped for uttering words, but Viki’s comprehension was not much, either. Cathy Hayes estimated that Viki understood 50 words or phrases at three years old.
Similar heroic attempts in the 1970s to teach English to Cody, a young orangutan, were similarly frustrating. With intensive drilling, graduate student Keith Laidler taught Cody to say “kuh” for a reward. Cody enjoyed this accomplishment and would say “kuh” to himself while playing with his toys or looking out the window. Since Cody had been taught to say “kuh” for a variety of rewards, clearly “kuh” meant “gimme.” Then Laidler started teaching Cody to say “puh.”
Aha! Now “puh” meant gimme! Cody learned to say “puh” and refused to say “kuh.” At this point Laidler decided that the sounds needed to have distinct meanings and defined “kuh” to mean “beverage, please” and “puh” to mean “food, please.” With more drilling, Cody regained the use of “kuh” and could use both words appropriately. Then Laider decided that “puh” should mean “pick me up” and a new sound, “fuh,” should mean “food.” Okay. Cody learned these definitions in three days and used his three words appropriately, but stopped vocalizing spontaneously.
Laidler laboriously taught Cody to say “thuh,” which obviously means “brush me.” Cody adored being brushed.
None of Cody’s words were necessary. He was perfectly capable of letting those around him know that he wanted food, drink, to be picked up, or to be brushed, using looks and gestures, but Laidler persisted in setting these maddening tasks before he would give Cody what it was obv
ious he wanted.
Cody tried his words on inanimate objects. When he was one, he was playing in his crib with a test table that rested across the top of the crib, banging it about and hanging from it. Somehow Cody got it wedged at the back of his crib and couldn’t get it loose. He tugged and tugged without success. Finally he shouted “kuh!” Nothing happened. He shook it angrily and shouted “puh!” This was apparently what the table wanted to hear—or else the shaking dislodged it—and the table came away in Cody’s hands, and he settled down to chew on it happily.
Laidler suspects that this incident reinforced Cody’s hope that objects would obey his magic words. Once Cody wanted to leave his playroom and go watch TV, but he couldn’t reach the handle of the door. He sat facing the door and commanded it to puh. Nothing. “There followed a puzzled silence, during which Cody’s eyebrows jigged about on his forehead like two demented caterpillars. Another commanding ‘puh’ and another long silence. I could almost hear the wheels and cogs grinding their slow tortuous course as he tried to work out just what was amiss. His face brightened momentarily as the answer broke upon his tiny brain. Then his visage darkened and like some sorcerer conjuring unknown powers to his own fell purpose, Cody rose unsteadily to his feet, raised his fisted hand and shaking it high with tense frustration, called upon the door to open with a loud ‘thuh.’”
Laidler then compounded the misunderstanding by lifting Cody up to reach the door handle.
Ask Alex what he thinks
When psychologist Irene Pepperberg set out to teach an animal to speak English, she chose a species that had the physical ability to do so, the African grey parrot. Alex is a now-famous parrot who’s been taught to use words with comprehension by Pepperberg. He’s been the subject of television programs, magazine stories, and journal articles exploring his linguistic prowess, not to mention Pepperberg’s book, The Alex Papers. His working vocabulary includes numbers, colors, shapes, materials such as paper or wood, and objects of interest to parrots, such as seeds, nuts, and things it’s pleasant to destroy. He has also learned words and phrases that weren’t explicitly taught, such as “Come back,” “Go away,” “No,” and “I love you.”
Becoming a Tiger: The Education of an Animal Child Page 15