Mind of the Raven: Investigations and Adventures With Wolf-Birds (25 page)

Their next meeting was with Murphy, my daughter’s lively, wolf-colored German shepherd. The dog was treated with considerably more respect than the fowl, but with at least as much interest. At first, the ravens made high-pitched, upward-inflected alarm calls. But Murphy paid no attention. She sniffed all around and within seconds settled down to chew on a frozen calf as all six ravens swirled around her. The birds were excited, squeezing out one fecal dropping after another, which kept getting smaller with each one. Within a minute or two, all of the ravens except White had flown out through the open door and into the side aviary to perch safely and silently up on the high perches in their shed. White, the normally totally silent bird who was at the very bottom of the dominance hierarchy of this
group of ravens, behaved entirely differently. Not only did she stay to watch Murphy intently, but she also kept following the dog, and she swooped over the dog repeatedly, making rasping calls. Blue, the undisputed large dominant male, continued to cower silently up under the protective shed in the adjoining aviary, along with the others. Within minutes, White’s vociferations grew louder. Soon they were deafening and she became ever more animated! She not only chose to stay in the same aviary with the large dog, but she began an extraordinary display I had never seen her do before, which was out of character with her otherwise meek postures and demeanor. She stood tall, held her bill high, erected her ear feathers (a display of power and dominance), fluffed out her throat and spread her shoulders (also parts of the dominance display); then she backed up these postures and feather displays with an amazing range of vocalizations in an endless spirited, loud monologue, an unbroken series of long trills, loud yells, high, rapid series of
yips
that switched now and then to low, rumbling, rasping growls. The sounds ranged back and forth from squeaks, so high in pitch that her voice broke, to low, deep, rumbling sounds. All of this was accompanied by wildly gesticulating head and wings. Every few minutes, she stopped for a few seconds to swoop once more over the dog’s back, making uniformly deep, long, rasping calls, the same kind the birds make when confronting any strange animals, and sometimes also strange ravens. Her animated behavior startled me, because she had been almost silent for months. She also had never acted “macho” before. She had changed from a wallflower to an engaging, happy, confident, and powerful personality. I doubt that the display was for the dog, though; perhaps she realized that she was alone, and that the others would keep their distance.

After four separate ten-minute sessions of Murphy in the aviary, none of the ravens had come close enough to yank tail, as a previous group of much younger ravens did within a minute or two to an old, lame husky I had introduced to them.

My experiments with barnyard fowl and household pets may seem inconsequential, but they were informative. They showed that ravens
go to some lengths to try to get acquainted with strange large creatures they don’t know. After they get to know them, they either ignore them or try to kill them. Knowing this, however, is no substitute for seeing what actually happens in the field, where the real test comes as they face big, fierce carnivores.

I had made plans years earlier to travel to Yellowstone Park and to Oregon, where colleagues had kindly volunteered to set up carcasses for me to watch wild ravens interacting with naturally occurring competitors and carnivores. Wolves had not yet been reintroduced to Yellowstone, but coyotes there (unlike in Maine) were diurnal, and I was curious how they interacted with ravens. Unfortunately, when it came time to use my airline ticket, I had reached a critical point in a radio-tracking experiment and was unable to leave without putting this ongoing work into jeopardy. However, I found an eager volunteer, Delia Kaye, who gladly accepted the challenge to be my emissary, with the understanding that she would take extensive notes.

Delia went to Yellowstone Park in mid-February 1992, where she was hosted by John Williams, whose team of researchers was studying the pack behavior of coyotes. The park ravens were not food-stressed. As is usual near the end of winter when ravens begin breeding, there were winter-kill elk carcasses all around. These were so abundant that many had no ravens feeding from them at all. The birds apparently preferred only the freshest, just-opened carcasses.

Delia was on hand to see one pack of coyotes begin to tear into a bull elk that had just died. Within several minutes after the coyotes had torn a hole into the neck, two ravens arrived and started feeding as well. The coyotes occasionally lunged at the ravens, but the birds merely jumped aside and came right back. Most of the time, the ravens, whose numbers quickly increased to about a dozen, fed unmolested with the coyotes nearby. The birds seemed surprisingly relaxed in the company of the coyotes.

In Eastern Oregon, the situation was entirely different. Gary Clowers, our host there, had set out a deer carcass near Grandview on the eastern base of the Cascade Mountains. From a blind made near
this carcass, Gary and Delia kept watch for four days. No coyotes came, but as many as twenty-six ravens were present at a time. Unlike at Yellowstone but much like in Maine, these birds did not quickly descend to the opened carcass. Instead, they loitered about in the vicinity, acting fearful of the unattended carcass.

Typically, all the ravens assembled on the ground about ten to fifteen yards from the carcass, then started to approach it as a group. Coming closer, two or three birds might haltingly edge toward the carcass, drawing others behind them. Then they would all jump back again and fly off. As in Maine, whenever they drew near the carcass, they walked hesitatingly, opening their bills in fright and performing what looked like numerous jumping jacks. Even on the fourth day, with twenty ravens routinely near the carcass, only two individuals approached it close enough to feed. These results were almost precisely as those I was used to seeing in Maine. But there was a big difference. Instead of all of the crowd eventually ending up at the carcass, most of the ravens got their meat without ever needing to go near the carcass they feared. They used intermediaries. The dozen or so magpies at the site showed no hesitation about feeding from the carcass. Neither did four eagles (two immature and one adult bald, and one immature golden). The eagles freely walked up to the carcass to feed, showing no hesitation at all. As a magpie, raven, or eagle left with meat, members of the timid raven crowd would take up a chase. Only birds leaving the carcass with food were chased. Up to four ravens might chase a single eagle or magpie. Magpies quickly dropped their prize when pursued by ravens, but whether all the eagles dropped their food could not be determined since the eagle-chases went far out over the countryside.

In New England, there are no magpies, and eagles are rare. Blue jays and crows, unlike magpies, don’t come near a carcass with ravens. The strategy of stealing food from intermediaries rather than approaching a feared carcass is less effective in Maine, but I have on numerous occasions seen ravens that have secured a piece of meat, when chased by other ravens, drop their meat routinely to terminate the chase. At dumps gulls are similarly chased by ravens until they give up their food morsels.

Along the Maine coast, bald eagles were fed at supplemental feeding stations for several years to prevent them from migrating south and becoming contaminated with pesticides. These feeding stations became prime
raven
magnets, attracting huge crowds of them. The ravens did not ignore the rare eagles. They treated them as my young aviary birds had treated the chickens and turkey when they first met them—they edged up behind them to yank their tail feathers. Were they trying to tell them something, discourage competition, find out something, or impress potential mates with their daring? There were hints here that the ravens’ lives are interdependent with other animals at and around carcasses, although I did not yet suspect the true relevance of these interactions.

C
OMMUNICATION CHANNELS IN THE
animal world include those of touch, sound, sight, and scent. Electric eels even use electric pulses. Insects communicate their sexual readiness and their location by scents, sounds, and movements. In our social interactions, we communicate all sorts of information unconsciously, using our eyes, gestures, tone of voice, and facial expressions. Ravens also are very expressive. By a combination of voice, patterns of feather erection, and body posture, ravens communicate so clearly that an experienced observer can identify anger, affection, hunger, curiosity, playfulness, fright, boldness, and (rarely) depression. The ravens’ calls have one basic message, which is to draw attention to themselves. Beyond that, they
also indicate functions: feed me, stay away, come here, recognition. Increasing specificity comes from context. The specific calls are not used as language. Ravens don’t have calls symbolizing carcass, eat, come, meat, et cetera. Ravens can’t say, “Come with me to that carcass to eat some meat.” Such communication implies complex thoughts. Ravens don’t think with words. If they think, it is with images, as we do when we don’t use words; but the basic logic of communication remains.

As an example of the logic of communication, let us reconsider a simple case: the loud begging cries of young ravens. The begging is understood by the parent to mean that the young need to be fed. Of course, the young can “lie”—in their competition with one another, they can try to outshout the others to get more than their fair share. I mean this in an unconscious sense, because I’m referring to evolutionary logic. A high cost of that loud begging could be the attraction of predators who would eat
them
. That would be
information transfer
to predators, but not
communication
. Information transfer occurs between young and parents, and in that case there is communication, because both signaler and receiver benefit. But the costs and benefits to the participants may vary, and evolution within both participants acts to minimize costs. Why raven young are especially noisy relative to most other young birds can be seen from the “experiments” that evolution has conducted over millions of years. We find, for example, that young woodpeckers safely ensconced inside fortresses of solid wood are even noisier for their size than ravens. Young woodpeckers make a din that scarcely ever stops, whereas the young of all ground-nesting birds, who are extremely vulnerable to predators, are almost totally silent except for the few peeps they make at the precise moment that a parent visits the nest with food. We can conclude, therefore, that young ravens, like young woodpeckers, are proximally noisy because they are hungry, and ultimately very noisy because of their relative safety in their hard-to-reach nests. There is little cost to their being loudmouthed; they can “lie” and act as if they are starving when they merely have an appetite. No mental awareness is implied in any step of this process.

The communication described above conforms to the theory called the Handicap Principle, as promoted by Israeli biologist Amotz Zahavi.
Much of animal signaling makes sense according to this theory. It says that in order to be effective, signals must be reliable. And in order for the receiver to know they are reliable—for the receiver to treat them seriously—they must be costly to make, for example, by attracting predators. If they were not costly to make, then signalers could “cheat” or give false information. This logic, however, is not always easy to apply to ravens’ vocalizations, as the following examples suggest.

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 After
word), 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.