At dusk on September 7, 1997, a cougar crept up on Ginny Hannum as she was working at the back of her cabin at the head of Boulder Canyon in Colorado. The cougar crouched low among the rocks, facing her from about twenty feet, and it was ready to pounce. Hannum, at ninety-eight pounds and four-feet-eleven-inches tall, was a well-chosen target.
Although Mrs. Hannum was unaware of the cougar’s presence, she had become “somewhat annoyed” by a raven “putting on a fuss like crazy.” “I never paid much attention to ravens,” she told me, but “this one was so noisy that it was downright irritating.” The noisy raven kept coming closer, having started its commotion twenty minutes earlier from about three hundred yards away. Hannum had never before noticed ravens “cackling like crazy.” Was this raven trying to say something? She started to listen more closely.
The cougar was ready to make its kill, but the raven was close, and it made a pass over the woman, calling raucously, then flying up above her to some rocks, where she finally saw the crouching cougar. As the cougar glared down with yellow eyes locked onto hers, Hannum quickly backed off and called her three-hundred-pound husband. The surprise attack had been averted. She had been saved. She recounted, “The lion moved his head just a little bit as the raven flew over it. That’s when I saw him. I never would have seen him otherwise. He was going to jump me. That raven saved my life.” The event was declared a miracle in the news.
A miracle is any event the natural cause of which we do not understand. That provides an adequate number of miracles to some of us—certainly to me. Why did the raven call? To the religious Hannums, it seemed a miracle that a raven would go out of its way to deliberately save a human life. To me, raven behavior is still a miracle, although I have faith that this raven’s behavior was within the realm of what ravens normally do. They are alert to predators that could potentially provide them with food, as well as to anything strange in their environment. Perhaps the raven had been luring the lion to make a kill, alerting it to a suitable target. If the lion had feasted, so would the raven. That is, both would have benefited, as expected in communication.
David P. Barash, a professor of psychology and zoology at the University of Washington in Seattle, wrote to me about two observations he made that suggest, but do not prove, that some ravens may follow cougars to feed on their kills. Barash was working on his dissertation research on the sociobiology of marmots in Olympic National Park when he saw a cougar stalk and kill an adult female marmot. He recorded in his notebook that “within seconds,” the cougar carrying the dead marmot was followed by two ravens. Who followed whom? Had the cougar perhaps at first followed the ravens?
A similar account with a possibly similar scenario appeared in the Anchorage Daily News (December 29, 1998). In this incident George Dalton, Jr. came face to face with a grizzly bear on a hunting trip near his village of False Bay. George had wounded a deer and he followed its blood trail into the brush where the deer went to die. The bear found the deer and also wanted to lay claim to it. After some tough negotiating with the bear, who was stomping angrily on the ground, George told him (in Tlingit) to please leave him alone. The bear came closer nevertheless. Soon George could smell the bear’s breath, and fearing for his life, then said to it: “OK, you can have him. He’s yours,” while backing away and retreating into the brushy muskeg. George recounts that the bear made a charge: “Ravens were following me and squealing. I thought they were guiding me and telling me that the bear was still following me.”
My interpretation here is also precisely the opposite. I suspect the ravens were not warning the man, but informing the bear of a potential victim instead. The ravens have a lot to gain if a bear makes a kill. They were probably guiding it to an intended, perhaps prechosen victim. Everything I know about ravens, as well as folklore (see Afterword), is congruent with the idea that ravens communicate not only with each other, but also with hunters, to get in on their spoils.
Whatever else these two incidents illustrate, they show the difficulties of interpreting communication, and how much interpretation can depend on the mind-set of the receiver. The Hannums and George Dalton thought the ravens were communicating with them. Instead, the ravens were probably informing the predators. To make sense of communication, the first relevant questions to ask are: What are the costs and the payoff to the givers and the potential receivers of the signals given?
Since prehistoric times, ravens have been thought to have divining powers. Ravens were first kept in the Tower of London because of their vocalizations, which were thought to warn of approaching danger, much as the Hannums and George Dalton believed they were warned of the predator. No bird calls have generated more excitement throughout history than those of the raven. Even now, the calls of the raven seldom fail to excite those that hear them in field, forest, and mountaintops. In a 587-page book on communication in birds, titled Ecology and Evolution of Acoustic Communication in Birds by Donald E. Kroodsman and Edward H. Miller, published in 1996, however, there is not one peep about the raven, although it lists the genus Corvus as “particularly worth investigating.” We know infinitely less about vocal communication in ravens than we know about the call of a frog, a cricket, or the zebra finch. That disparity reflects not so much lack of interest as our inability to get replicable data. The more complex and specific a communication system becomes, the more random-sounding and arbitrary it will appear. We will have trouble distinguishing it from noise. Any meaning that we can find should be welcomed.
In one study completed in 1988, Ulrich Pfister of the University of Bern in Switzerland spent one winter recording all the vocalizations of raven pairs living within about 1,000 square kilometers south of Bern. Of the thirty-four different call types that he recorded, fifteen were individual-specific, eleven sex-specific, and eight specific to the ravens of that area. His associate Peter Enggist-Düblin since then has made 64,000 additional recordings of raven calls near Bern. New calls kept turning up with each raven pair examined until, after analyzing seventy-four individual ravens from thirty-seven pairs, Peter brought the total to eighty-one calls. Even more calls would presumably have been found if more ravens had been sampled, even in just that one study area. On an informal basis, I still recognize new raven calls almost every year in my Maine study area, even after fifteen years. I hear distinctly different calls in every area outside New England where I’ve been. There are tremendous variations of intonation and dialect, and I’m not at all sure that what I perceive as one call type is not really many, or vice versa. But what are the meanings? Peter concludes from his work that ravens’ calls do not all have the same meaning. Rather, some calls’ meaning are context-dependent and established by convention. They are then culturally transmitted.
In a letter Peter acknowledged to me that: “We have difficulty publishing our ideas, which, in our own opinion, go beyond, and are therefore also a critique of the current understanding of communication in animal behavior science, which seems for some referees hard to handle.” I would soon enough find out the truth of his observations.
I made only an informal short glossary of some seventeen common raven calls from my two tame pairs, Fuzz and Houdi and Goliath and Whitefeather (see Table 16.1). Seven were restricted to one sex only (four to male and three to female), and of these seven, four were given only by one of the four individuals, and then only after the birds were more than a year old. That is, the trend was for sex-specific calls to appear when the birds were older, and some of these calls were also individual-specific. I was unable to decipher innumerable other nuances that occurred routinely, and was forced to be a “lumper” of calls rather than a “splitter.” Mine was only a rough personal probe without systematic recordings. I wanted to distinguish the calls by ear, so that I could then routinely “watch” these birds in the field with my ears when I could not see them in order to possibly do a more systematic study later if I should detect an interesting hypothesis to test. Despite the crudeness of my method, I did find something significant:
Regardless of the type of call, dominants of each sex may effectively silence all or almost all calls of others of their respective sex in their presence (see Table 16.1). For example, while confined exclusively as a pair with her mate Fuzz, Houdi made 804 of the 2,309 calls I tabulated in May 1995. Four months later, the Fuzz-Houdi pair was combined with the Goliath-Whitefeather pair in the same aviary. Houdi (no calls) and Goliath (13 calls) went nearly silent as Fuzz and Whitefeather then made most (467 and 338, respectively) of the calls. I again separated the two pairs, Fuzz-Houdi and Goliath-Whitefeather, and during December-January Houdi and Goliath became vocal again, making 380 and 902 of the total of 6,570 calls I tabulated.
By and large, my efforts were a confirmation of what Pfister and Enggist-Düblin also found. Some of the raven calls they recorded were common to all the birds, but the majority could be learned and culturally passed on. Even within the 1,000-square-kilometer Swiss study area, there was an east-west geographical separation in distribution of call types. The greater the distance between nests, the fewer call types were shared between them. Some individuals at the dialect boundary were “bilingual” for certain call types. Since some of the calls were strictly specific to males and others strictly specific to females, it was concluded that there is a tendency for males to learn the calls of other males, and females to learn those of other females. There was also a tendency for mated pairs to share calls.
Ravens are well known for their capacity to mimic, especially if they are isolated from others of their kind. Mukat, a lone resident in a cage at the Living Desert Museum in Arizona, makes a perfect rendition of portable radio static. A raven used for physiological research outside the biology building at Duke University perfectly mimics a motorcycle being revved up. A couple of the raven’s perhaps more interesting and unusual vocalizations were related to me by David P. Barash. While David was studying his marmots at a colony in early June in Olympic National Park, he distinctly heard, “Three, two, one, bccccchhh,” (the last a guttural sound of about four seconds’ duration, serving as an excellent imitation of an explosion). The sequence was repeated at least three times. He wrote me, “It sounded so realistic that I looked around for the speaker, even calling, ‘Who’s there?’ out loud, despite the fact that this risked disturbing the marmots I was supposed to be watching.” It turned out that the “speaker” was a raven, perched on a nearby snag. Park rangers had conducted avalanche control the previous week, and apparently the raven had heard, and been sufficiently impressed. David continued, “Later in the summer, I would commonly hear the rushing, gurgling sound of urinals flushing. Again, the culprits were ravens—at least two different ones this time. There was a picnic area about a half kilometer away, outfitted with toilets whose urinals automatically flushed every thirty seconds or so. Ravens often perched atop these structures.” And they apparently were at least as impressed with those sounds as they were with those from the avalanche control crew.
An intriguing question is whether or not ravens can learn arbitrary sounds and then associate meaning to them. For example, babies may at first babble and make sounds like “mama” or “dada” that they only later associate with the appropriate subjects. Darwin, the raven that Duane Callahan is currently training for wilderness rescue work in California, gives hints of recognizing the meaning of sounds he makes, perhaps because he gets rewarded with certain coincidental associations. For example, he has learned what the words “Want to go outside?” mean, because Duane always uses them before he takes him out of the house for his free flight. He may also have learned “Duane, Duane” from Susan and Duane’s brother Charles. Now Darwin says, “Duane, Duane, want to go outside?” when he wants to go out. He is, in effect, perhaps asking to go for a walk. Darwin also perfectly mimics Charles’s raucous laugh. Sometimes when the telephone rings and Duane answers, “No, Charles isn’t here right now,” Darwin will erupt in the background with “a perfect rendition of Charles’s laugh.” Is it sheer coincidence? Does the raven hear “Charles,” and knowing who that is, then think of his laugh?
The ravens’ vocalizations invite comparison with our language, and with that comparison in mind I was especially interested in the development of language in my son. Eliot’s first sounds were cries of emotion, signifying discomfort, surprise, contentment, or anger. Parents are able to decipher at least some meaning from context, much as I can often learn meaning from a raven’s calls from context. Eliot’s other early vocalizations were sounds of recognition. On seeing a cat, a dog, a car, or a turtle, or almost anything else that surprised him, he said, “Da, da, da—” and the number of times he repeated it was variable, depending on his surprise. I suspect that like the raven’s rap-rap-rap calls, his vocalizations meant, “I see, and I’m interested and surprised.” The next stage in vocal development concerns specificity. For example, ravens’ various levels of surprise and alarm are expressed at different predators or potential predators, although there are no raven words for them. If specific calls have meanings, they can be correctly interpreted only by those other ravens who regularly associate with that particular individual and thus know what sound is associated with what object. It was similar with Eliot. At age twelve months, for example, wetness or anything liquid was “juice.” He divided the animal world into “dog” (all furry animals), “turtle” (reptiles and beetles), and “fish” (pisces of all the various orders as well as dolphins). “Dada” was dad, and curiously, also some men and any ape. In time, he would distinguish ever finer details, and the sounds he made would have specific meaning to an ever-greater circle of others beyond parents, relatives, and associates.
After Goliath and the other three ravens of his group settled into their roost to sleep at night (when less than a half year old), I often opened my bedroom window into their shed and talked to them as one might to a baby. They always answered with soft, low murmurs—km, mm. When the murmurs were very low, soft and long and almost whispered, I learned the birds were at ease, as could also be seen from their relaxed postures. The calls seemed to be contact calls meaning, “I hear you. Everything is fine.” The young gave the same calls with a slightly upward inflection when we explored together in the woods and lost visual contact with each other. I presumed in that context they meant, “Where are you?” because when I answered the birds, they responded without that inflection, and I knew they had heard me and were still in contact. If they were being attacked by a predator, I’m certain I would have known it from their calls as well. I’m also certain nobody else would who did not know the birds.
Their intimate calls at the evening roost were usually almost whispers when we were very close together. I was reassured by their whispers and I reassured them. After our chat was finished, I sometimes heard a muffled shake of feathers, little zipping sounds of pinions drawn through bills, rapid dull scratching of toenails on the back of a head, and hollow-sounding footsteps as one shifted along its wooden perch. After I closed the window, I occasionally still heard a soft cough or a stirring on a branch. These sounds had meaning to me, because they said something about the behavior of the birds on the sleeping roost.
As my ravens got older and more independent, they chatted less with me. Instead, they woke me at the first sign of dawn with raucous calling. Perching on the windowsill, they pointedly peered in and made mostly bouts of rap-rap-rap calls and also deep, penetrating, long rasping caws. Both calls were otherwise given when raven intruders came near. Here in a different context, they had an entirely different meaning. My ravens wanted my attention and food. They got it, and thus I reinforced their specific vocal behavior. When they were hungry, they also gave long, drawn-out, high-pitched calls, which I call their “beg” or “yell,” and they stopped after I fed them.
Still other calls draw attention and probably say, “Here I am,” but from a very long distance. These are probably territorial calls because they can be heard for miles, and are usually answered by neighbors but never attract them. There are several of these loud, long, penetrati
ng calls that are used equally by both sexes. I suspect they are less to get attention, as such, as to say, “This area is claimed.” When these calls are directed at ravens within visible contact, the callers erect their “ears,” flare their shoulders, and puff out their throat hackles. The macho display is omitted when the same calls are directed to me. I presume that their intent is to get my attention, because my tame birds stop giving them after I open the window and greet them.
Numerous other raven calls are given in what appear to be specific circumstances, when one emotion should predominate and be expressed as casually and without conscious intention as eagerly jumping off a perch at dawn. For example, one might expect alarm when a human or other predator approaches the nest. Instead, many different kinds of calls may be given, and the mix of calls varies from one pair to another. A seemingly much more alarming situation, such as capture, never evokes a sound from them. I suspect that calling when they are vulnerable and helpless could attract predators, not helpers, and so silence is then golden. There are numerous nuances of comfort sounds, yet recently captured wild birds give no “shouts of joy” on release from one’s hand. In that case, calling to reveal emotion would serve no purpose because there is no potential listener that could benefit them for giving the call. However, that’s an oversimplification—ravens often vocalize without any apparent listener near.
Raven Number 34 was an example. He was one of twenty-two wild-caught birds I had released after I had kept them in the aviary for over a year. After these birds left, Number 34 remained, perching alternately on top of the aviary, on a beech to the left of it, or on a big red maple to the right of it. For hours, he sang. His song was so uplifting and exuberant to my ears that I got out my tape recorder and started recording. I sat down less than fifteen feet from him and he paid me no attention. He was gurgling, chortling, yelling, trilling, bill-snapping, quorking, and making sounds like water rattling pebbles. The bird made no female knocking sounds, so I speculated that it was probably a male, but I could not be sure.
Mind of the Raven: Investigations and Adventures With Wolf-Birds Page 23
