We don’t have to learn to see and hear, although we get better at these things as we mature. Nature and nurture interact nicely so that neurons connect up in response to light and sound impinging on our senses. We learn where the sound is coming from, however, and how to turn our heads to look at it. If young animals don’t get the sensory input that the world almost invariably supplies, things can go wrong. Barn owls who have had an earplug inserted in one ear learn to localize sounds based on what they hear, and know precisely where a sound is coming from. (This is key information to a barn owl when the sound is a mouse rustling in the hay.) When the earplug is removed, the world sounds different, and they’re wrong about where the noise is coming from. They learn better in a few weeks. An owlet is still growing, and its ears are getting farther apart. Since part of the way birds and mammals tell where a sound is coming from is by (unconsciously) comparing the sounds reaching the two ears, growing owls need to be able to adjust to changing sound cues.
Eureka! I have drunk it!
It’s not enough to see. We also need to understand what we see. Baby chicks do not know what water looks like. They get thirsty, and when they have water in their mouths they drink gratefully, but even the thirstiest newly hatched chick will walk witlessly through puddles without suspecting that help is underfoot. But chicks automatically peck any irregularity they see, and so they peck at floating specks on water, get their beaks wet, and instantly make the connection.
Water in any form can be mysterious. Limpet, a young captive-reared otter, stepped out of her sleeping box one day and saw her first snow. Three times she huffed in suspicion, then walked out into it. Snow turned out to be wonderful, and at once Limpet shoved her head under it and raced forward, hurling a fan of snow into the air.
J. David Henry, who follows wild foxes through Prince Albert Park, has seen several foxes learn about ice. In late November, a lake may freeze over in the night with smooth dark ice. Henry described the encounter of The Prince, a particularly noble young fox, with frozen water. The Prince came to the lake to drink and bumped his nose. He sniffed at the ice. No scent. He waved his forepaw over it and experimentally scratched at it. Hard. Carefully, one paw at a time, The Prince stepped out on the ice, which bore his weight. Solid. Gaining confidence, he walked, sniffing at the ice, and then trotted, as foxes do. A foot slipped. The Prince turned and smelled at the slippery spot. He proceeded, and several more times he slipped, stopped, turned, sniffed. “Then suddenly he burst into a galloping sprint. Legs slipping and sliding everywhere, the fox for a moment was going nowhere; it was clearly a peculiar sensation for a normally graceful animal. The fox then raced across the surface and came to a sliding, half-stumbling stop, followed by a playful twisting leap into the air.” Until the snow fell, The Prince punctuated his hunting schedule with breaks for ice dancing. He loved to get up speed, galloping, and then slide across the ice crouched on all four legs or seated on his rump.
Controlling the body
Before The Prince became a fox who could gallop, sprint, slide, or even walk, he was a blind sprawling cub. He was born in a dark earth where there was little to see, and his eyes didn’t open for more than a week. By the time a month had passed, he had grown remarkably, his eyes had opened, and he and his siblings were preparing to stagger out of the den, look around, and start playing. But he didn’t have to learn to grasp.
Hand control was a problem for Cody, a baby orangutan. He wanted to put his fingers in his mouth and suck on them, but it was hard to get them to the right place. Keith Laidler describes eight-week-old Cody waving his hand about, jamming it in his ear, making expectant sucking motions with his mouth, and looking puzzled.
Comparing the way four different baby primates began to grasp things, Francesco Antinucci found that a baby crab-eating macaque walks (on all fours) at an early age, before it has developed hand coordination. As a result, when the little macaque wants to examine an interesting thing, it can and does walk over and explore it with its mouth, tasting, gnawing, or picking it up in its mouth.
A baby gorilla is already developing substantial hand coordination by the time it can begin to get around, and develops hand-eye coordination shortly thereafter, so it initially investigates things with its mouth but soon is about equally likely to investigate a fascinating object with mouth or hands. A baby capuchin monkey is already working on hand-eye coordination when it begins to walk, and so it investigates things mostly with its hands. In this capuchins resemble human babies, who handle things before they are mobile.
Isn’t that baby walking yet?
All primates look slow compared to animals with precocial young who stand, walk, and even run shortly after birth. Although humans take around a year, it’s not that we’re complete idiots, it’s just that we’ve evolved a different strategy. An infant fawn or a foal can run away from predators when it is still very young, whereas we rely on our mothers or fathers to carry us away. But even the infant prodigies of precocial species have some difficulties.
Sarah McCarthy, a veterinary equine specialist, who’s seen a lot of baby horses born, says that foals know how to stand up shortly after birth. “Some foals are stronger or more coordinated than others, but the program seems to be there. Most normal foals will stand up within a few attempts, and then improve dramatically with each success such that by the time a foal has gotten up by itself even two or three times, it is generally very good at it. Within a few hours they can pop up on their feet instantly.
“In contrast, lying back down again seems not to be automatic at all. Some foals figure it out very quickly and it is not much of an issue. But others struggle with the concept. They stare at the distant ground with consternation, start to fold their legs, decide it is just too far, chicken out, try again, decide they did not really want to lie down anyway, go have a drink, try it again, give up and fall asleep on their feet, etc. They may hit the ground in quite a heap too. It can take several days for some foals to master this maneuver with any grace at all.
“Length of leg does seem to be an issue, and really leggy foals seem to have more trouble than stouter ones.” The foals that figure it out generally get down by folding all four legs at once. The foals who struggle try this, which can be difficult, and also try folding the rear legs first, that is, they sit down. Or they try kneeling, folding the front legs first, which often results in “an absolute face-plant.” Adult horses fold their front legs first to lie down, but foals are usually so disproportionately long-legged that this doesn’t work for them.
Why is standing up easier than lying down? Standing up is important, because young hoofed animals must stand to nurse. Presumably gravity will always bring a young animal down once it gets tired enough, so standing up is the part where innate hints are needed.
The truth about great apes like us is that when we’re born we sort of know how to walk. One well-known infant reflex shows this. If you hold a baby a few days old so that its feet gently touch a surface, the baby will often take steps with alternate legs. It is not possible to build on this and have your child walking by the end of the week—its head is too heavy, its muscles are too weak, its balance is wholly inadequate. We’re talking about a kid that can’t even hold its head up yet, so have patience. Babies walk when they’ve matured enough to walk, and even if they’ve spent much of their infancy strapped to a cradleboard, they walk at the same age.
That’s just gas
If you’re going to make others wait on you hand and foot for years, you’d better be charming. Human babies and chimpanzee babies accordingly smile or make play-faces much earlier than baby rhesus macaques, which are mobile at a few months old. Unlike a fox, born in a dark den but walking in weeks, primates are born with open eyes, and we can look into our parents’ faces.
Toddling down to monkey town
Infant chimpanzees have one huge skill which all the primates except us have: they cling like a burr. Mother monkeys and apes can use all four limbs to get around, and don’t have to
use their arms to support their babies. Newborn chimpanzees need some help holding on, and their mothers get into the habit of affixing the baby more firmly to them before they move off. Very young chimpanzees cling to, and are held against, their mother’s abdomen. When they are as young as eight weeks they may ride on her back. For quite some time they can’t change position on their mother’s back, and if their mother boosts them onto her back facing backward, backward they stay, looking over their shoulders to see where they’re being carried.
As baby chimpanzees get older, their mothers encourage them to walk (on all fours, first) by putting the babies down and backing a short distance away. Then the mother looks at the infant with friendly grunts and facial expressions until the baby lurches toward her. A chimpanzee mother has also been seen encouraging an older infant to walk on two legs by taking its hands and walking backward, encouraging the infant to stagger after her. Eight-month-old baby chimpanzees begin tottering away from their mothers, since they are now able to turn around and look for her. The first time the wild chimpanzee baby Prof deliberately let go of his mother Passion was when he was dangling from a small branch in front of her. After letting go of her, Prof hung silently for a moment and then grabbed his mother again.
Of Lucy, a chimpanzee raised in a human home from two days old, it is reported, “At two months her eyes would focus and follow a bright object, and at three months she could walk about on all fours. At five months she was trying to climb out of her crib to go to people, and at six months she was pretty mobile on all four limbs, though she did not walk on two legs till she was about eight months old.”
At three months old she was a cuddly infant who loved to kiss and be kissed by all and sundry. By three years old she did some of the things very mischievous human toddlers may do, such as grabbing the end of the toilet paper roll and dashing through the house with it. But she also did things toddlers seldom do, such as racing along the mantelpiece hurling ornaments to the ground or climbing a standing lamp and leaping from the lamp to a fixture.
The infant orangutan Cody was slower than Lucy, and didn’t try to crawl until he was eight months old. His foster father, Keith Laidler, anxious to pour knowledge into the little ape, kept trying to get the baby to sit up. “At 12 weeks, whenever I sat him upright he would collapse forward, his hands at his sides, making no attempt to save himself from the inevitable bump on the floor. Time after time I tried it, and time after time Cody would end up with his nose against the boards, staring in shocked silence at the floor”
Many of Cody’s developmental milestones came between those of chimpanzees and gorillas on the one hand, and humans on the other. He crept at 26 weeks, later than the average chimpanzee or gorilla (20 weeks), but much earlier than human babies. Like some human babies, he later came up with a wacky mode of locomotion for which it seems unlikely there are innate motor patterns: scooting. “He could not yet manage a straight one-two-three-four movement of limbs, but instead pivoted his bottom over and around his legs, these remaining immobile until his derrière had reached terra firma. Once he had bottom-landed, his legs would move again to a forward position, and he would once more lift his rear in a little arc over his legs. His later efforts were also a bit of a hit and miss affair in that he would attempt to raise all four limbs together (no one had told him about gravity) and, with a little cry of indignant surprise, fall flat on his face.” Crawling was not far off. “Within two weeks he had discovered the most efficacious form of locomotion on four limbs, and from then on my life was hell.”
Learning to use your trunk
Elephant calves stand shortly after birth and soon walk. But a calf must also learn to operate its trunk, a limb with nothing like the evolutionary history of a leg, but with 50,000 muscles just waiting to be told what to do. When calves don’t pay attention, they step on their trunks and trip. To drink water, the baby kneels and uses its mouth, rather than taking water in its trunk and squirting it into its mouth, as adults do. A calf spends many diligent hours trying to control the thing, flopping it about, twirling it, sucking on it, attempting to pick up ever tinier objects.
Learning to climb
Three orphaned bear cubs, Squirty, Curls, and The Boy, raised by Benjamin Kilham from the age of 7 weeks, got their first chance to climb trees at 13 weeks. “Although their climbing skills were unformed, the cubs knew immediately how to go about developing them, especially how to reach down with their feet to find a footing, and were tenacious about practicing and learning.” Within three days they were adept.
Baby howler monkeys begin climbing by swarming around on their mother’s body, interspersed by sticking their fingers in her mouth, ears, and eyes. Then, still holding on, they reach out and grab branches. When they’re a little older they let go of her and climb on branches for 10 to 30 seconds at a time. A few months later the infants climb around, jump awkwardly in the branches, and “plop” back and forth near their mothers. They begin hanging by their tails for a minute or two and wrestling clumsily with other babies. One-year-olds “doodle,” hanging by their tails for long periods, swiveling around, and touching leaves and twigs. Sometimes two monkey children wrestle, swat at each other, or hug while hanging by their tails. Once an observer saw two juveniles hanging by their tails side by side in front of an adult, who pushed them gently so that they swung like pendulums.
Captive baby rhesus monkeys without playmates practiced climbing by assigning themselves “projects.” Can I leap straight up to that branch? Can I jump from the post over to the side of the cage? Can I jump back? Okay, I’m going to climb up that pole, jump over to the mesh, and climb down the mesh, and I’m going to do it really fast. Okay, this time after I climb down I’m going to hop over to the pole.
Climbing trees comes naturally to chimpanzees when they’re old enough—when they’re used to it. At the age of 14 months, Lucy, a chimpanzee raised in a human home, was terrified when her foster brother set her on a low branch in a mimosa tree. Later she enjoyed climbing trees, but with nothing like the ease of wild chimpanzees. In the woods, she’d climb one tree, climb down, and climb up the next one, disappointing her foster father by never swinging or even clambering from tree to tree. When, years later, as part of a reintroduction effort, she needed to climb trees in Africa to get food, she made a poor showing.
When the other chimps climbed a wide-trunked baobab tree to eat its fruits, flowers, and leaves, Lucy found the going too hard. Lucy, who had learned about 100 ASL signs in her previous life, began signing to Janis Carter, who was supervising the reintroduction effort. “More food,” signed Lucy, “you go.” She pointed to the tree. Her idea seemed to be that Carter should climb the tree and toss food down to Lucy. “No,” signed Carter, gesturing to Lucy to climb an adjacent, slenderer tree and jump across to the baobab. Lucy led Carter to the baobab, stationed her hands on the trunk, and signed, “More food, Jan go.” Carter refused (she does not say whether she could have climbed the baobab if she had wanted to, but that is not the point) and went back to camp—followed by Lucy—and found a large piece of timber, which she began to drag to the baobab. Oh, okay. Lucy helped Carter drag the timber to the tree. Then Lucy propped it against the trunk and climbed up.
What do you see when you look in the mirror, big guy?
Orangutans are, in a leisurely way, superb climbers and clamberers. They are also heavy, so branches that are superhighways to squirrels or long-tailed macaques are no use to them. Female orangutans weigh around 40 kilograms (around 90 pounds) and males weigh 80 to 100 kilograms (180 to 220 pounds). Since trees are not always obliging enough to grow large sturdy branches that reach to large sturdy branches in the next tree, orangutans have other ways of getting from tree to tree. Biruté Galdikas has described how an orangutan gets into a “pole tree” that sways under its weight and deliberately makes it sway farther and farther until the orangutan can grab the next tree over. If the ape tests a pole tree and finds that it’s not strong enough, it may grab two pole trees at once, a
nd use them together to sway in an arc to another tree.
Anne Russon describes how wild orangutans treated pole trees “as if they were down escalators, letting their weight bow the tree right to the bottom then stepping off neatly.” A two-year-old apeling practiced swaying, sitting in a small tree and shifting his weight to make the tree sway in different directions for different distances.
It looks natural enough when wild orangutans do it. But the captive orangutans being released at Galdikas’s rehabilitation center didn’t find it so easy, never having learned to judge trees and their trajectories. They liked the idea of traveling on high. But they would try to clamber through skinny saplings that crashed beneath their weight, and they tried to sway trees that were too stiff to budge. Accustomed to swinging on steel chains, they swung on lianas that often broke. They kept on making these mistakes for months, and after years in the forest often preferred to descend to the ground and travel there, which limited them to places where there were trails.
So sophisticated are the skills needed for such a heavy animal to move around in trees that biologist Daniel Povinelli and anatomist John Cant have argued that it requires self-conception. Smaller primates (and other smaller arboreal animals) can get around in trees using a limited set of stereotyped motor patterns, they argue. But orangutans need to execute “unusually flexible locomotor patterns” and need to be more alert to the possibility of things moving, bending, or breaking beneath their weight. In a 1995 paper, Povinelli and Cant give the example of an orangutan in a tree reaching out and grabbing the ends of a bunch of small branches with one hand or foot, taking hold of a liana with another hand or foot, pausing to survey the situation, using a third hand or foot to hold another bunch of branches, letting go (with the fourth hand or foot) of the tree where it is perched, and swinging across a gap into another tree. Orangutans are notoriously slow-moving, and perhaps this is connected with their frequent need to ponder the angles.
Becoming a Tiger: The Education of an Animal Child Page 5