Authors: Bernd Heinrich
Tags: #Science, #Reference, #bought-and-paid-for, #Non-Fiction
John Sawyer, a neighbor of mine in the nearby village of Weld, had on numerous occasions seen one of my ringed ravens behind his house. This raven knew his cats. One day, hearing the raven call loudly, John saw his cat approaching out of the woods, carrying a mouse. The raven hopped right behind it onto the lawn, then erupted in loud caws. The surprised cat stopped, and in the instant that it looked back, the raven rushed in boldly, grabbed the mouse, and flew into a tree to eat it while the cat meowed in frustration. The raven had gauged all of the cat’s moves perfectly.
There are innumerable reports of ravens presumably showing their bravery to impress potential mates, as they pull wolves’ or eagles’ tails. In four days of almost continuously watching dozens of ravens feeding along with wolves at Shubernacadie, Nova Scotia, in March 1997, I did not see the behavior once. On the other hand, I have seen all of my young ravens exhibit equivalent behavior within minutes of being exposed to a dog or cat. After observing only wild birds, I had originally theorized that, to use an analogy of Indian braves touching their enemy with a lance, ravens “count coup” with wolves and other carnivores to show “bravery” and gain status with mates. I now know I was wrong. I reject this hypothesis because of new evidence: First, the behavior is most prevalent in young birds long before there is any
mate bonding. Second, birds do it in total isolation, without any potential audience; and third, it is not associated with
ritual behaviors used to impress potential mates. All three points are in concordance with the idea that the behavior is play, and that the play serves in education. Ravens do not, of course, try consciously to educate themselves. They act out neutral patterns that have evolved to be internally rewarding, because those individuals that are proximally rewarded in behaviors that ultimately benefit them engage in them more, survive, and leave more offspring.
Sometimes it is the seemingly senseless little things they do that make me wonder if they can be motivated by thought, or whims, rather than blindly following a programmed script. On the morning of February 19, 1998, I went to visit and socialize with my birds in the aviary, as I did almost every morning. There was an abundance of food: one cottontail rabbit, one side of calf, and two partially eaten gray squirrels. Yet, as always, the birds followed me and loitered around me like so many stray puppies. Blue and Yellow made comfort sounds and edged up to me, making eye contact. Mostly it was Green who caught my attention, as she tried to pick a three-inch rock out of ice on the ground. She worked diligently, and when she got it out she dropped it and tried to get another more challenging one that was embedded deeper. Giving up on that one, she then found three more rocks that she did dislodge from the ice. Usually as she was working on one rock, the other birds would come over to watch, help for a while, but then wander off. One rock she got loose weighed nearly a pound. I never saw her, or the others, ever again take an interest in rocks.
Ironically, throughout the animal world, a variety of play behavior is generally acknowledged to be correlated with intelligence, even though doing senseless things only for the fun of it as opposed to some purpose is thought to be stupid. I suspect that play is almost literally like intelligence. Play is an acting out of options, among which the best can then be chosen, strengthened, or facilitated in the future. The difference is that with play, the options are all played out overtly, not only in the mind. With intelligence, only the best options (and some of the worst) are played out overtly, and often much more quickly.
Ravens may look at you with one or both eyes. This bird has been digging in the snow with its bill, after sufficient exercise to heat its bill so that snow melted and stuck to it
Marzluff and I had caught another group of ravens from a feeding crowd. As usual, most of these birds were pink-mouthed, immature vagrants, but three of the crowd were dark-mouthed. We felt we could have captured a mated pair among these three, since adults commonly travel closely together in pairs, especially at this time of year near the beginning of the nesting season.
We marked all the birds with wing tags, then released the pink-mouthed birds into the main aviary and segregated the three adults into a side aviary. Two of the three adults almost immediately preened and made soft cooing sounds to each other. They seemed glad to be together, and neither of them interacted with the third. Seeing these social developments, we removed the third bird to leave the couple in
its new “territory.” For two years and three months, they became key players in several studies.
This pair of wild birds did not nest that first spring, but by the second spring, they built a nest in their shed and then raised four young. In the third spring, they rebuilt the nest, but the male got out through a hole in the chicken wire. He stayed in close contact with his mate by frequent calling and by perching on the trees nearby.
After being free ten days, the male still had not abandoned his mate, and we were hopeful of luring him back inside. To try to catch him and still keep her, I cut a hole at snow level in one side of the aviary where I installed an inward-directed two-foot-long funnel of wire mesh, like a lobster trap. I placed meat at the end of the funnel and hoped that it would attract the female. The male might then be directed through the funnel to meet her and the food. I anticipated that once inside the aviary, he would fly up to his familiar perches and be caught.
I did not anticipate correctly. He did gain access to the meat and his mate inside the aviary, but he went back through the tip of the funnel and escaped again. It was now my move. I built a blind in the snow nearby, under the branches of a large fallen pine tree, and waited there until he went back into the cage. I planned to jump up and run and yell as soon as he was inside. Ravens have lightning-quick flight responses. I guessed that in the excitement, he’d lose his head and fly straight up. I tried my ruse. In response to my yells and mad rush toward him, he suspended his natural impulse to fly up. Instead, he did the more difficult thing. He attended to what was relevant in the totally new situation. He sought out the narrow entrance hole of the funnel instead.
My move again. I camouflaged the hole so that it was difficult to see from inside the aviary. The funnel had been straight, but now I angled it, then stuck twigs into the snow around the funnel entrance. The raven had no problem solving the first part of the puzzle—he got into the aviary through the obstacles, and his mate joined him on the ground. He then stayed close to the funnel entrance, as if ready to make another quick getaway through the exit. I gave them several minutes, hoping his attention would wander. Then I jumped up and yelled like a banshee. This time the raven missed the camouflaged
entrance. He flew up and didn’t have time to find the hole before I got there.
This incident engaged me for two reasons. First, I had no idea that a raven would so faithfully return to its mate and/or nest; and second, I was surprised at the bird’s escape through a funnel, a strange new contraption that all ravens fear and would normally avoid, when before he had always flown
when disturbed. I doubt if any other bird would have been able to keep track of such a specific escape route, or to concentrate on precise and strictly relevant factors despite major distractions. Did the bird have insight into spatial relationships?
We all have “cognitive maps,” which we use to correctly negotiate over territory. By use of our mental maps, we can return home without having to retrace the exact path we used when leaving. Ravens may also have a cognitive map of their territory, although we have no way of knowing. Their reactions to three-dimensional geometry may be easier to examine.
Each morning at dawn, Houdi and Fuzz pounded on my bedroom window and called loudly until I got up and gave them a treat or a toy. One morning, I gave them two shiny pennies. Fuzz carried both in his throat pouch, then stuffed one of them into the crack behind a two-inch-wide branch nailed onto the side of a post. Stepping to the side and using the point of his lower mandible, he hacked a sliver of bark off the branch and used this sliver to cover the penny. Houdi watched him, and several minutes later came to retrieve his hidden penny. It was too deep in the narrow groove to be grasped from the top, so she pounded it down instead, repeatedly peering down below the branch to see if it had appeared yet on the other side. Fuzz came, and shoving her aside, first looked at the top and then the bottom.
I later gave Houdi a rectangular piece of cheese on the same high platform outside my window beneath her nest then containing young. She tried to cache the one-and-a-half-by-two-inch cheese by inserting it into one of the two-inch spaces between the floor beams. At first, she held the narrow side of the cheese into the gap, where it would have fallen ten feet down to the ground if she had released it. Normally, ravens simply drop food into cracks, but this one had no bottom. She
twisted her head around and inserted the broad side of the cheese, which fit snugly into the space. She walked away, then brought back a pigeon feather and covered the cheese with it.
On February 18, 1996, I asked Goliath to solve a geometrical puzzle by giving him a favorite food: corn chips. They were about two and a half inches in diameter, and I lay thirteen of them down. How would he handle them? He crunched three, one after another, and ate all the little pieces. Then he stacked four, one above the other. Lifting the four-pack, he flew off and cached it. Soon he came back, ate one chip, and again stacked four before flying off to make another cache. One corn chip was left. He came right back to eat that one.
Food is a reliable motivational tool for a raven, allowing one to try to trick the trickster. Lorrell Shields told me about an Alaskan oil pipeline worker who, for amusement, tried to frustrate a begging wild raven by throwing it
donuts. The raven wanted to fly off with both, of course, but a raven can grasp only one at a time in its bill—at least, so the pipeline worker thought. This raven, instead of grasping the first donut with his bill, stuck its bill through the hole in the donut. That left its bill-tip free to grasp the second donut. Then it flew off with both. Similarly, Terry McEneaney saw a raven in Yellowstone make off with a roll of toilet paper. The ends of the roll were too thick to get its bill around, but the raven carried the roll by sticking its bill into the center hole.
Two ways to carry two donuts at once
As already mentioned in the Preface, unlike all other Passeriformes, or perching birds, ravens occasionally use their feet in imaginative ways that could involve insight. If not, why do some of the thousands of other species with the same tools not do the same? Ravens are the only passerines who may carry objects, including eggs, in their feet in flight. Rare individuals may also carry multiple food items in their bills in surprising and equally imaginative ways. I talked with Peter Kevan, an entomologist,
who saw a raven fly into a tree where there was a grackle nest with half-grown young. Instead of taking many trips to carry these young off individually, the raven emerged from the tree with the whole nest in its bill. Similarly, one year when the crossbills nested in abundance in the red spruces on Bald Mountain, I found a crossbill nest at the edge of Webb Lake, discarded on the snow beneath a raven’s nest. Had the raven carried the whole nest back from the mountain?
It is potentially conceivable that using nests as baskets is innate. However, it seems difficult to envision evolution encoding the fine arts of cracker stacking, donut handling, and toilet paper carrying in ravens specifically, or that these skills were learned after lengthy trial-and-error behavior.
In fall 1995, I wondered if my four untrained two-and-a-half-year-old ravens at the time were as clever as the Alaskan bird was reputed to be at the donut-handling task. To find out, I left six Vermont Koffee Kup Bakery donuts in the open air for a week to firm them up a bit, and dumped them into a pile in the aviary with Fuzz, Goliath, Houdi, and Whitefeather. It was their first exposure to donuts. I expected the well-fed birds to cache the donuts for future use, rather than eating all six of them on the spot.
In fifteen seconds, Fuzz stood over them, glancing repeatedly at the other three birds, who kept their distance. He bent down to feed on one donut, and Houdi, his preening partner, started to come near him. He rebuked her only mildly as she grabbed a donut and flew off with it to eat it alone. He stayed and leisurely fed in place, then picked up a stray twig from amongst the donuts, and walked four feet away to cover the twig with pine needles as if he were caching a donut. At four feet, he was still close enough to defend the donut pile from Goliath and Whitefeather, who came down to try to get their share. Seeing them approach, Fuzz chased them off and resumed casual feeding. Next, he picked up another piece of debris and cached that nearby also, while continuing to cast glances at his two fellow ravens, whom he still had managed to render donutless. Returning to the donuts after his trash cache, he took a few tiny bites, then cached a donut inside a nearby plastic drain tube. In three leisurely trips, he brought pine needles and other debris to shove in behind the donut. While he was thus partially diverted, Whitefeather managed to find an opening to fly down and grab a donut. Three down, three to go.
Having cached one donut, Fuzz casually ambled back and took his second from the pile, walking with it into the weeds about six feet away. This time, he made four separate leisurely trips with debris to cover the cached donut. Goliath, who had not yet had a taste, watched the whole time and made repeated tentative approaches. Whenever he tried to get within four to five feet of the donuts, Fuzz drove him away.
Fuzz returned to the two remaining donuts, again walking nonchalantly. This time, he finally picked two up at once. He did it in a unique way that seemed to me at least as clever as the Alaskan’s. He put only his upper mandible through the donut hole, then he maneuvered the second donut to lie horizontally on his lower mandible so that the lower curve of the vertical donut was partially inserted into the hole of the horizontal one; the hole of the lower donut served as a basket for the upper. He then left to cache the two. This time, instead of staying nearby, he flew far; he no longer had to simultaneously guard any remaining donuts while caching those he held. However, he had
possibly miscalculated Goliath and/or forgotten the already cached donut. As Fuzz flew off, Goliath immediately flew down, yanked the plug out of the tube, and grabbed Fuzz’s first cached donut. Fuzz quickly came back after having cached his two donuts, and he chased Goliath all over the aviary until the latter dropped the stolen goods.
Maine ravens obviously knew how to hold their donuts, but if they seemed a little more idiosyncratic or creative than the Alaskan raven, it was probably because the Alaskan pipeline workers eat bigger donuts than those from the Koffee Kup Bakery. The donuts I used were a puny three inches across, but I had enlarged the hole to one inch.
When I gave the ravens four similar donuts two weeks later, Fuzz at first guarded them, pointedly watching all the other birds. He again made a fake cache nearby with a piece of debris before caching a real donut. Houdi checked the fake cache. Fuzz saw her and then recovered his just-cached donut, bringing it back with him to the pile. He next made four false caches of twigs and bark. He again went to the trouble of covering the trash he had cached with billfuls of dead pine needles. After the fifth false cache, Fuzz finally cached, in a great rush, three donuts within ten feet of the donut pile he continued to guard. I knew with near certainty that if he flew off to cache at a distance, where they couldn’t see him, he would immediately sacrifice what was left. Did he? Was that why he made the false caches—to try to confuse the others, who he knew would try to recover the caches they saw him make? Was he lying, playing, or engaging in displacement activity because he didn’t know what to do?