What produces the style differences between Vogelkop bowerbirds in the two areas? It seems clear that learning is involved in making bowers and, for the females, in choosing the best bowers. “Females sometimes go about in groups to visit bowers, so that younger females might learn taste in bowers from older females,” writes Diamond. Scientists comparing the mitochondrial DNA of Vogelkop bowerbirds from two populations, one of mimimalist spire builders like those in the south Kumawas, one of baroque hut builders like those in the Wandamens, found only slight genetic differences. It may be that the birds, driven by their artistic differences, will eventually become separate species.
No one understands my art
Then there is the mysterious case of stone handling. Japanese macaques living on Arashiyama, a mountain near Kyoto, have since 1979 been fooling around with stones every day for no clear reason. (I am including it here in case it’s art.) The first monkey seen doing this was Glance-6476. She had carried some flat stones out of the forest into an open feeding area. She stacked them up, knocked them down, and scattered them with her hands. No other monkeys were seen doing this. But in 1983, when zoologist Michael Huffman resumed observing the troop, there were lots of monkeys doing it every day.
After feeding time (eating provisions put out for them), monkeys rest, play, and groom. Some of them fill their cheeks with grain and handle stones while slowly chewing. Although the forest is full of stones, monkeys may steal stones from each other. If these stones are more desirable, their excellence is based on criteria that humans haven’t discerned.
In 1983, Huffman categorized eight ways of messing with stones: gathering them into a pile in front of you; picking then up; scattering them; rolling them in your hands; rubbing them together; clacking them together; carrying them somewhere; and cuddling them against you. By 1985 he added: repeatedly dropping the stones; rubbing them on a surface; striking two together in a “flinting” gesture; and picking up, rubbing, and clutching smaller stones or gravel. The younger monkeys came up with these.
Older monkeys don’t handle stones as much as younger monkeys and they do fewer things with them. “Older individuals tended to become more conservative in their stone-handling behavior,” says Huffman. Stodgy monkeys with their old-school stones.
The females Glance-6476, her cousins Glance-6775 and Glance-6774, and Blanche-596475 were the oldest stone-handling monkeys, the only ones in their generation to do it. The children of stone-handling mothers all handle stones, and Huffman suggests that baby monkeys find the sound of clacking stones familiar, since they were able to hear it in the womb. But monkeys whose mothers didn’t handle stones also learned to do it, as in the case of Glance-69’s baby, who tried to pick up stones when it was two weeks old. No monkey learned to do it after they were five. It seems that the custom at first spread within age groups and then was passed down to the children of handlers, who spread it in their own age groups.
If a young monkey is handling stones and its mother comes up to administer a grooming, the child will keep going while its mother grooms it. “When a stone handler is approached and solicited, for example, to play or copulate, he or she will sometimes abandon the stones and join in, but more often than not, the invitee will ignore the solicitor entirely.” Oppress-7079, a macaque who gave birth to her first child, “did not at first appear to know what to do with her infant.” She didn’t seem comfortable when it tried to cling to her so this irresponsible, pleasure-mad young monkey handed her baby to a male, Deko-64, and went off and handled stones.
Fads
Some cultural phenomena spread obliquely through a group and then die away, passing novelties. One summer a pod of killer whales in Canadian waters went wild over headstands. For a killer whale this means treading water vertically while your tail is sticking straight up out of the water. If you do it right, your tail rises, majestically, higher and higher out of the water, but it takes practice not to wobble and fall over. By next summer headstands were over. No one was doing headstands.
At an oceanarium in Hawaii, where the rims of the tanks extended up to about human waist level, a fashion for leaning took hold among the dolphins one summer. Suddenly they all wanted to see how far they could lean out of the tank and balance on the edge of the wall. Sometimes a dolphin overdid it and fell out of the tank. Staff got annoyed, because picking up a 400-pound bottlenose dolphin and heaving it over a barrier is hard work, and what if a dolphin fell out at night when no one was around? Whenever staff saw a dolphin balancing on the wall they yelled and ran over and pushed it back in the water, but the dolphins seemed to find that even more entertaining. The staff were greatly relieved when the fad passed.
Humpback whales learn their famous songs, which change from year to year. (So, perhaps, do the less-studied bowhead whales.) All the males in an area sing the same song. Marine biologist Michael Noad has listened to thousand of hours of humpback song. In 1995 and 1996 he heard 2 out of 82 whales on the east coast of Australia singing the same kind of song west coast whales were singing. In 1997 many eastern whales began singing the western song. Most sang either the old eastern song or the new western song, but three whales had a song that combined the two. By 1998 every whale was doing the new song. Noad thinks the craze (which some popular commentators compared to the British Invasion of the 1960s and Noad compared to the advent of punk) stems from the fact that female whales get bored with the same old songs. He should know. Of his work, he remarked, “It’s pretty soul-destroying in some ways, sitting there and listening over and over to whale songs.”
Lions in Lake Manyara National Park were noted to spend a lot of time relaxing in trees. Whenever they had nothing to do, they did it in a tree. Lions in the Serengeti were far less likely to be found in trees. George Schaller examined possible reasons why the Manyara lions might be so arboreal. While lions in Ngorongoro Crater were reported to have retreated to trees during a plague of biting flies, there was no plague of biting flies going on in Manyara. Lions sometimes escape from hostile elephants or buffalo by climbing trees, but there was no plague of elephants. The trees were no different from Serengeti trees. Since the flies seemed no more pesky, the elephants no more savage, the buffalo no more intemperate, Schaller speculated that a prolonged epidemic of flies in the past might have gotten Manyara lions into the habit of retreating to the trees, and then, after the plague was over, the lions transmitted the custom culturally.
Learning to be a social animal—how we do it here
Katharine Milton observed a small colony of spider monkeys that had been created by placing 20 mostly juvenile animals on Barro Colorado Island, feeding them for a while, and then leaving them to their own devices. These animals had been bought in markets and probably had all been caught as infants from the wild (by means of shooting their mothers) and subsequently kept as pets. Fifteen vanished, and the remaining 5 juveniles survived and multiplied to a population of 12 at the time they were studied. Despite having had no wise elders, they had a normal spider monkey social structure and ate a fruit-supplemented-with-bugs diet such as wild spider monkeys customarily eat. (One cannot rule out the possibility that the 15 monkeys who vanished were eating the wrong stuff.) Milton takes from this the lesson that before one rhapsodizes about the plasticity of primate behavior and the “potential for innovation” they display, one should note the “monotony of much primate behavior” and the way that “species-typical behaviors are manifested with monotonous regularity and from study site to study site.” She argues that environmental differences produce only “minor modifications” to this tedium.
Milton makes a good point, but it may also be that the environment in which they were released—one where spider monkeys had lived in the past before being exterminated—was like other spider monkey environments and helped produce standard spider monkey behavior. If they were in a genuinely different environment (spider monkeys in the desert! spider monkeys at the beach! spider monkeys on the moon!), it might produce a different social structure and
dietary changes.
You’re telling me that’s normal?
Frans de Waal, who proposed the concept of reconciliation in nonhuman primates and pioneered its study, did an interesting experiment with two species of macaques. Stump-tailed macaques are large and rather peaceable for macaques. They are gentle and tolerant, less obsessed with dominance ranks than rhesus macaques, and they have a large repertoire of reassuring gestures. They use these when they reconcile after fights, and they reconcile three times as often as rhesus monkeys do if they have a fight. Don’t they sound nice? But their tails are mere stubs.
With student Denise Johanowicz, de Waal set up a mixed colony of juvenile macaques, consisting of some two-year-old rhesus and some two-and-a-half-year-old stump-tails. They chose older stump-tails in the hope that this would make them more influential.
The rhesus were frightened by the big stump-tails. While the stump-tails wandered about looking at their new accommodations, the rhesus all clung to the ceiling in a worried bunch. After a few minutes the braver rhesus, though still hanging on to the ceiling, grunted threats at the stump-tails. A dominant rhesus would have answered back and a subordinate would have run away, but the stump-tails ignored it.
Eventually the rhesus came down from the ceiling and the species mingled, although at night they slept in two piles, one of stump-tails and one of rhesus. Again and again the rhesus found that the big, confident stump-tails, clearly dominant, were unaggressive. The two species played together and had the usual quarrels, but the stump-tails were amazingly—amazing to the rhesus—eager to reconcile with their opponents. The stump-tails were also anxious to groom the rhesus, a friendly act that was probably accelerated by the stump-tails’ fascination with the lovely long tails of the rhesus. By the end of the experiment, all the monkeys slept in one big furry pile.
More important, the rhesus monkeys had changed an aspect of their behavior. They had not adopted stump-tail gestures or calls, but they had increased their rate of reconciliation dramatically. They now reconciled just as often as stump-tails did. After five months, the stump-tails were taken out, and the rhesus monkeys went right on reconciling like civilized, mature primates. They still acted like rhesus, but now they acted like really nice rhesus. Rhesus monkeys make a soft, pleasant sound, “girning,” to show friendly intent, and these rhesus were big girners.
It may be that with an inverted experimental design, with older rhesus and younger stump-tails, the stump-tails could have been taught not to be so ready to reconcile, could have learned to be touchier. But if the researchers had to pick one experiment, they picked the right one, for it is more impressive to learn that animals can be encouraged to be sweeter than to learn that they can be encouraged to be meaner.
If you don’t like it, why don’t you leave?
The fact that the aggression level of primates varies among groups can be seen in some large colonies of chimpanzees. The captives have tons of free time to spend on their social relations, and they can’t get away from each other, so they have stronger reason to seek harmony than wild chimpanzees. This may produce different rules for acceptable conduct, particularly limits on male violence against females and infants. In places like the Arnhem Zoo, the Netherlands, these limits are enforced by coalitions of adult females of a kind that do not seem to exist in wild groups.
In some zoos, there are no such coalitions. In a private zoo, two chimpanzees lived in a small, old-fashioned cage, an iron-barred, concrete-floored box 5 meters by 10 meters. There was a 15-year-old male, Bonz, and a 33-year-old female, Jingles. Both had been raised by humans. Jingles’s only pastime was begging for food from visitors, but Bonz had two pastimes, begging for food and terrorizing Jingles.
Her life was miserable and had been for years—and then the zoo opened a new exhibit, an enclosure of almost an acre, with grass, trees, and a stream. There’s a fake termite mound where chimps can dip for peanut butter. They sent Bonz to another zoo and put Jingles in the new exhibit with two juveniles who had been raised by their mothers. The juveniles explored with enthusiasm, chasing toads and chipmunks. Jingles did not seem to grasp that all this space was available to her. She stayed within 100 feet of the entrance to the sleeping quarters. She seemed “almost agoraphobic.” When the young chimpanzees first groomed and hugged her, Jingles would start with terror. “I don’t think anyone had hugged her before,” reports Kathleen Morgan, who with her students studied the effects of changed environments on captive primates. Jingles eventually learned to groom and hug. One day she even crossed the stream.
Paternalistic culture
In the 1950s, Japanese primatologists watching macaques noticed that, in some troops, adult males cared for young monkeys during the four-month-long season when the females were giving birth. They called this phenomenon “paternal care,” although it is unlikely that the males could know which infants were their own. The “paternal” monkeys were tender and vigilant, and did everything for the one-and two-year-olds that their mothers did, except for nursing them. Each male developed a relationship with a particular infant. This was first noticed in the Takasakiyama troop. A survey of other troops showed no sign of paternal care in eight troops, one or a few examples of it in seven troops, and a strong tradition in two troops. The paternal males clasped the infants, carried them on their backs, groomed them, played with them, and threatened tourists and primatologists who got too close to them. The babies were even permitted to grab food that the males were preparing to eat. This behavior started abruptly when the first baby of the season was born. Sometimes a baby was cared for by a male both during the delivery season when it was around one year old (8 to 16 months) and in the following year. Thus the infant Cob, who could be identified by her limp, was cared for by the male Pan two years running.
Cob was a big crybaby, and Pan was aggressive. “When he is protecting an infant, he becomes especially furious,” writes primatologist Junichiro Itani. One day Cob got frightened when tourists tossed peanuts noisily, and she ran away crying “Ki. Ki. Ki.” Pan raced over, clasped her, and threatened the tourists. When Cob ran off to play, Pan tried to attack the tourists.
Uzen, a sociable and ambitious but unaggressive macaque, was very fond of children and was so often seen gathering half a dozen and playing with them that researchers nicknamed him “Kindergarten Teacher.” Observers felt that this gave him improved access to the central part of the troop, where the highest-ranking macaques spend their time. He almost always had an infant clasped to him when he entered the central area, perhaps “playing the part of a passport for the central part of the group.” This may have contributed to his rise in status.
It would be lovely to think that the male macaques of Takasakiyama got together and decided that mothers needed help with child care when they had new babies, but that doesn’t really seem like macaques. And it would be sociobiologically interesting to hypothesize that in a troop where males take care of the older infants at this difficult time, more babies survive, and so more of the males’ genes are passed on—or that males who care for infants are more likely to rise in rank and conceivably to leave more descendants as a result—but there’s no reason to suppose that the difference in this behavior among troops is genetic. The primatologists concluded that it was a behavior elicited when males saw other males caring for infants, and passed on culturally.
Were you born in a barn?
Biruté Galdikas describes social gaffes committed by young orangutans who are being reintroduced to the wild after having been partly reared in captivity. They do not know how to keep a proper social distance from adults and are apt to offend by walking too close to them or trying to climb into their nest. Since the orangutan response to an orangutan faux pas is sometimes to bite big holes in the other orangutan, learning manners is very important.
Mandara, a three-year-old gorilla raised by humans, was placed in a zoo exhibit with Tomoka, a large, gentle silverback. Tomoka had lived with other gorillas for years, although not with baby g
orillas. He knew how a male gorilla starts a conversation with a stranger—by showing how impressive he is. He strutted around, pounding on his chest. The only gorilla Mandara knew was a younger playmate, and so she assumed that Tomoka was inviting her to play and she chased him. The more fiercely and impressively he strutted, the more she frolicked. When she simply wouldn’t get the message, Tomoka snatched her up, put her on the ground facedown, opened his jaws wide, and pressed his enormous teeth against her back. Then he walked away. Mandara, shocked but unhurt, got up and sat in the corner. She was a quick learner, and when she was introduced to the other adults, there were no such crossed signals.
Lion lore
Elizabeth Marshall Thomas has described a change in the culture of lions in the Kalahari Desert. When she and her family lived there in the 1950s, the local people, the Ju/wasi, showed them how to behave around lions and how to expect lions to behave around them. The attitude was one of cautious respect. The message to be conveyed by each party was “We won’t bother you if you don’t bother us.” When lions and people met in the bush, for example, the thing to do was to “walk purposefully away at an oblique angle without exciting the lion or stimulating a chase.” And this was what the lions did, too. No one loses face or shows weakness by retreating, and no one provokes anger or alarm by advancing. Simultaneously, lions and people recalled business elsewhere. (I saw this courtly routine performed when bird-watchers and a black bear family met on an Arizona mountain trail. The bird-watchers, going uphill, suddenly preferred to look for birds on their right, and the mother bear, coming downhill with her cubs, remembered something that needed to be investigated off to their right.)
Becoming a Tiger: The Education of an Animal Child Page 31