Strier didn’t hug them, badly though she wanted to, because she intended to remain a passive observer, not an active participant in the muriquis’ life, and because she wanted to be certain that no disease or parasites were passed from her to the monkeys or the other way around. But she knew she had been accepted as a benign presence in their lives and ruled out as a predator.
Learning the bogeyman’s name
A vital thing that most baby animals must learn is who might want to eat them. It’s almost certain that somebody does. Even animals at the top of the food chain, huge and armored or bristling with teeth, start as infants, relatively tiny and tender and defenseless. And even those who don’t plan to eat a baby animal might harm it. On the other hand, being afraid of everybody is a lot of work, it disrupts your life, and it’s not even accurate—not everyone means you harm. It’s best to distinguish between enemies, friends, and noncombatants, as the muriquis did. Some of the ways animals do this are innate, some are innate but triggered by learning, and some must be learned more or less from scratch.
In early experiments on enemy recognition in birds, ornithologists Margaret Nice and Joost ter Pelkwyk raised song sparrow nestlings indoors and measured their reactions to things they might or might not view as threats. Song sparrows were an ideal species for such tests, they wrote, because they showed gradations of worry, unlike goldfinches, which were either indifferent or hysterical, with nothing in between. In the first, or “alarm,” stage of concern, Nice and ter Pelkwyk write, the song sparrow says “tchunk” and may raise its crest, raise and flip its tail, flip its wings, and change location. In the second, or “fear,” stage the bird says “tik” and compresses its feathers, elongates its neck, and crouches. In the third, “fright,” stage the bird says “tik-tik-tik” and flees, hides, flutters desperately, and pants with open bill. Most of the stimuli presented to their sparrows elicited varying numbers of tchunk calls per minute, which they graphed on what I can only term a tchunkogram.
Young hand-raised birds did not tchunk much at cats, although one of them not only tchunked but escalated to tik-tik-tik after spending some time on a screened porch where cats came to sit on the railings. Stationary (stuffed) hawks produced tchunking and tikking, but moving models of hawks elicited the tik-tik-tik of terror. Snakes weren’t scary, even when they were zipping around the room. A stationary (stuffed) barred owl produced steady tchunking and even some tiks, and was even more worrisome when it was placed on the Victrola. However, the young birds were getting used to it until they were treated to the spooky sight of the owl perched on the piano in the next room. For some reason this bloodcurdling vision made a lasting impression, to the extent that afterward they tchunked at the piano even when it didn’t have an owl on it.
Nice and ter Pelkwyk concluded that song sparrows know their enemies by a combination of inborn and learned patterns. Thus owls were innately scary, but piano fear was learned.
It’s a bird! It’s a plane! Oh no, it really is a bird!
Many young birds (and some mammals) respond with terror when a generic bird shape with a long tail and short head passes overhead. But if the shape passes overhead in the reverse direction, so that, although unchanged, it now appears to have a long neck and a short tail, all is calm and good cheer. In the first orientation the shape looks likes a hawk (particularly like a falcon or accipiter), a worrisome thing if you are small and tasty, but in the second orientation it looks like a goose, and few birds need to fear goose attacks.
This behavioral program has room for learning. Ellen Thaler, at the Alpenzoo in Innsbruck, compared the reaction to possible predators in chicks raised by mothers and hand-raised chicks. These were chicks of rock partridges, hazel hens, and rock ptarmigans. In their first week, all chicks were terrified by dummies of predatory birds being moved overhead; by an actual sparrowhawk that occasionally dropped by the zoo to see if lunch was being served; and by just about anything that moved quickly. They would give an alarm call, crouch, and freeze.
But as the weeks went by, the hand-raised chicks became blasé. They scarcely bothered to crouch and glanced only briefly at the predator. They often didn’t give alarm calls. By six weeks old, they didn’t even stop eating. They only responded when the wild sparrowhawk (a dedicated volunteer) flung itself against the bars of the aviary in attempts to grab them. They panicked, “more ‘hysterically’” than the chicks raised by their mothers.
Meanwhile chicks raised by their mothers continued vigilant, even though they had experienced the same number of threats. The difference seemed to be that they saw their mother’s reaction to predators, and that convinced them that they were right to worry.
Thick-billed parrots, some captive-born, some wild-born, were kept in outdoor aviaries in Arizona, awaiting release into the wild. From the aviaries they could see predatory birds, and captive-born parrots could witness the alarm of their wild-born companions. To drive the point home, goshawks sometimes went so far as to swoop down and hit the cage in attempts to find out how parrot tastes. The captive-born birds learned to respond to the thick-billed parrot alarm call. Despite this cautionary experience, many captive-born parrots were killed by goshawks and red-tailed hawks shortly after release, perhaps due to being insufficiently watchful. They knew they should be worried, but they hadn’t learned how to act on their worries.
Hawk shapes are scary, and so are eyes. As a result, many creatures are decked with eyespots that may cause predators to hesitate before grabbing them. Some researchers suspect that primates and perhaps other animals may have an innate response to leopard spots. The rosette spots of leopards, jaguars, and many smaller cats are believed to be an ancient pattern. Since spotted cats have been around for so long, primates have been around them for a long time. Bonnet macaques in an urban troop that had probably never seen a leopard were appalled when they saw a spotted model leopard and alarm-called like crazy. Not only were they upset by the sight of the nicely painted model, they were upset by the sight of a model made out of leopard-printed towels.
Researchers Richard Coss and Uma Ramakrishnan presented wild troops of bonnet macaques with leopard models and measured the level of their alarm. A realistic spotted leopard upset them much more than the same model upside down, which still upset them more than a leopard model in solid brown, which upset them more than the solid model upside down. When seeing a model with anomalous qualities, such as being upside down, they looked longer at it and also looked at other members of the troop, apparently to see how they were reacting.
We blame the snake
Many animals, including many primates, including many humans, are afraid of snakes. Whether this fear is learned or innate has been hotly debated, especially in the company of persons who state that they have an instinctive fear of snakes and other persons who want to prove to them that their pet Kaa, or Nag, or Ourobouros, is not slimy at all, but pleasingly smooth and dry.
As is so often the case, the truth is in between. It seems that many creatures are very ready to fear snake-shaped things that move in a snaky way, but although this often leads to fear of snakes, it does not inevitably do so.
If a rhesus monkey raised in a laboratory sees another rhesus behave fearfully around a snake, the first monkey will fear snakes too. Eight minutes of seeing the other monkey act fearfully at the sight of a snake is enough to produce a lasting fear. The newly cautious rhesus won’t go into a room where it can see a snake through a window, it won’t reach across a fake snake to get food, and its fear can infect a third rhesus with the same fear.
Snakes have been around for a long time, and many of them are dangerous. If you have to learn this by being bitten or even by seeing others bitten, that’s going to be expensive in terms of species survival.
Snakes are special. Researchers tried hard to instill fear of flowers in monkeys, using the same techniques that had produced fear of snakes, and they couldn’t do it. One researcher did induce observational fear of “arbitrary objects such as kitchen ute
nsils” in male rhesus monkeys. The first monkeys were shown the utensils and then frightened by blasts of air. The second group of four monkeys saw a monkey reacting with fear to the sight of the utensil, and subsequently three of them were fearful at the sight of the utensil. (Sadly, the crucial question of what sort of kitchen utensil it was is missing from my reference. If it was a potato masher, that is one thing, but anyone might fear one of the more elaborate corkscrews.)
A rhesus monkey can also learn that snakes are okay. If it sees that other monkeys are calm around snakes, it will itself be calm about them. It becomes “immunized,” in the sense that it is less likely to fear snakes through witnessing another monkey’s fear.
Viki, a chimpanzee raised by Cathy and Keith Hayes, had never seen a snake. One day, when Cathy Hayes was carrying Viki and a portable heater, the cord came loose and trailed behind them, and Viki flew into hysterics. “After that whenever I carelessly dangled the heater cord, she went into paroxysms of fear, and I philosophized upon the ancient enmity of primate and serpent.”
But then one day as they played on their Florida lawn, a black racer snake slithered within inches of Hayes and Viki, who looked “mystified,” but no worse. Hayes gave Viki a dead garter snake to play with. She didn’t find it creepy, even when Hayes trailed it over Viki’s toes. “But the instant her eyes fell on the heater cord, a frown appeared, her face flushed, and she burst out screaming. What was I to conclude but that Viki had an instinctive fear of electric-heater cords?”
Viki continued to find real snakes mildly interesting and enjoyed chasing them off the lawn. One morning Hayes and Viki went outside and nearly stepped on a large rattlesnake. Hayes grabbed Viki by the skirt of her adorable outfit, and hurled her away from the snake. Viki screamed, and the snake feinted at Hayes and slithered away. A week later they saw a coral snake in the garden, and both froze, Viki clutching Hayes’s skirt until the snake departed peacefully. Viki never chased another snake. (Whether she continued to fear the heater cord is not recorded.)
It seems that Viki had a predisposition to fear snake-shaped things moving snakily, which was triggered by the sight of the heater cord pursuing her. Real snakes didn’t trigger this predisposition until the day of the rattlesnake, when Hayes’s reaction left Viki in no doubt about how awful snakes are.
Afraid of snakes? Me?
For some animals, fear is not the best reaction to snakes. Bernd Heinrich presented a garter snake to his hand-raised great horned owl, Bubo. Great horned owls eat snakes and have no use for innate snake fear. This snake tried hard to be scary. It coiled, it flattened, it lashed about, and it lunged toward Bubo, showing the pink inside of its mouth. Somewhat flustered, Bubo leapt onto the snake, who promptly sank its fangs into Bubo’s foot. Bubo flew off, trailing the snake, and the snake let go and escaped into the woods. The next time Heinrich produced a snake, Bubo was more decisive, and after watching the snake do its intimidating maneuvers, leapt on it with both feet, crushed its head with his bill, and swallowed it by the head first.
Flenter, a bull terrier belonging to Kobie Krüger, also viewed snakes with hostile intent. He harassed a spitting cobra living in a flower bed in the garden of the Krügers’ house in a South African wildlife reserve. Naturally, being a spitting cobra, it spat venom in his eyes. The first time this happened, one of the family rushed Flenter to the nearest garden spigot and rinsed out his eyes. The second time it happened, Flenter rushed himself to the tap and waited to have his eyes flushed out. Subsequently, if there was no one in the garden to witness his need, he’d go to the kitchen door and howl for help and when someone came out, he’d dash to the tap. (His being a bull terrier, it did not occur to him to leave the snake alone. The Krügers’ Australian shepherd had no trouble with this concept.)
Mobbing
Birds sometimes assemble in mobs to scream at, taunt, threaten, and even attack predators, often going after birds of prey they find perched, uttering alarm calls, fluttering around them, perhaps swooping over their back or head and pecking at them. Mixed flocks of species, attracted by the sound of mobbing birds, may form if the target doesn’t move on. Daphne Sheldrick describes how Red Head, a wild red-headed weaver living in her garden in Kenya, became so tame that he would enlist her help in mobbing snakes, flying to her or her husband, uttering an alarm note, then swooping back toward the snake.
One bird-watcher described finding two robins, a catbird, two chewinks (towhees), and a hummingbird hysterically mobbing something on the ground in a cottonwood grove. When the birdwatcher investigated, she found a tiny kitten, eyes barely open. Well, they were right in principle.
In experiments on mobbing, Eberhard Curio put European blackbirds in compartments from which they could see another blackbird mobbing some object. By rigging the compartments suitably, Curio could delude the watching bird about what was being mobbed. For example, it might see a blackbird that was mobbing, and think it was mobbing a honeyeater, when in fact the mobbing blackbird was seeing and directing its mobbing at an owl. Curio designed experiments to test how easily blackbirds could be induced to mob a stuffed honeyeater, a large Australian bird that the blackbirds would not encounter in nature, as opposed to a multicolored plastic bottle about the size of a honeyeater. They learned to mob both but could never be convinced to fear the bottle as much as the honeyeater. The news that honeyeaters are enemies to be mobbed could be passed along a chain of six birds, each learning from the one before, without losing its power to inflame and outrage.*
New Zealand researchers used mobbing to teach New Zealand robins that stoats are dangerous. Robins on the mainland are appropriately scared at the sight of stoats. But Motuara Island robins know nothing of predatory animals, including stoats. These island birds did not fret when experimenters put a stuffed stoat near their nest, any more than they fretted when experimenters put a stoat-sized cardboard box near their nest. Experienced robins from the mainland were upset about the stoat but not about the box. To try to convince the naive islanders that stoats are bad, the experimenters set up fake mobbing events, involving a moving stuffed stoat with a dead robin in its mouth, playbacks of robin alarm calls, playbacks of robin distress calls, playbacks of blackbird alarm calls, a stuffed robin in mobbing position, and a stuffed blackbird in mobbing position. The blackbirds and blackbird calls didn’t impress the robins, but they found the other materials very persuasive and after only one exposure conceived a lasting distrust of stoats.
The takahe, a gorgeous blue-green flightless rail, must also contend with stoats, and researchers put on cautionary stoat acts for hand-reared takahe chicks. They were subjected to attacks by a stuffed stoat on a stick and by a stoat puppet, which swooped on them from above. They beheld a tragic melodrama in which the stuffed stoat attacked a takahe dummy. The dummy uttered distress calls until the stoat “killed” it. They also beheld a drama with a message, in which the stuffed stoat attacked a dummy takahe and the takahe fought back, pecking the stoat to “death.” They watched “intensely,” but although the chicks seemed more aware of stoats as a bad thing, and more cautious around them, they declined to actually attack the stuffed stoat themselves. Once released, the captive-reared takahes had as good a survival rate as wild-born takahes.
Dinner parties make me uncomfortable
Once you have learned to mob a scary bird like a hawk, it is possible to learn fine distinctions about which hawks are the scariest. Researcher Frances Hamerstrom wrote that it’s easy to tell by looking at a hawk whether it’s hungry. Falconers know that a hungry hawk looks “sharp-set” and will fly at game. Wildlife painters don’t always have this information. Hamerstrom writes that experts “are often amused by paintings of hawks with feathers and attitude of the body showing repose bordering upon somnolence but with talons ‘fiercely’ clutching prey.” If a falconer can tell when a hawk is hungry, can prospective prey do the same?
Hamerstrom took a tame red-tailed hawk out into fields around Plainfield, Wisconsin, and stationed him in plain v
iew to see if birds would mob him. For half the tests he was sharp-set and for the other half he had just eaten. He was much less upsetting to little birds when he was well fed, being mobbed by 12, as opposed to the approximately 100 birds who mobbed him when he was sharp-set. One kingbird was so maddened by the sight of him even when he was well fed that it dive-bombed the hawk and pecked him on the head, but kingbirds are touchy at the best of times.
Just as birds may learn that one class of hawks (hungry ones) is scarier than another class (sated ones), they can learn to distinguish individuals. Bernd Heinrich writes that the crows at Cornell have learned the menace that is Kevin McGowan, an ornithologist who climbs up to nests and bands baby crows. “He is singled out among all the students and professors for attack by crows when he walks across campus.”
Young magpies have a suite of innate fears, so that a hand-reared magpie rattled when she was introduced to a dog, and she was horrified when she saw her first hawk on the wing. She didn’t like the look of deer or bicyclists at first, but eventually learned that they were not much of a threat. Newly fledged wild magpies rattled at the sight of a vulture on the wing, but a week later they followed their parents in remaining calm and silent at the sight of a vulture. (While a vulture would happily eat a dead magpie, living creatures are in no danger from a vulture. It is a waste of time to panic at the sight of one unless you are concerned about the beauty of your corpse.)
Becoming a Tiger: The Education of an Animal Child Page 23