At two years old, the orangutan child Chantek pretended to feed his Cookie Monster sips of milk from a glass. (On the other hand, Andy, a capuchin monkey, made horrible faces and screamed when the Muppets came on television.)
Play in adults
Grown animals still play from time to time. An unusual example of play in an adult comes from Pigface, a Nile soft-shelled turtle who arrived at the National Zoo in 1940. Six inches long, he was not really pig-faced, but he had the pointy nose and wide decurved mouth appropriate to his species. By the 1980s, Pigface was a yard long, and violently bored. Once a week he received a nutritious dead rat, and twice a week a dozen live goldfish. The goldfish were the highlight of the week, and he pursued them “with speed and agility,” so zealously that until he caught them all he literally stopped only to breathe. This filled 20 exciting minutes a week.
In the 1980s keepers noticed that Pigface had begun to bite his front legs and rake his neck with his front claws, hurting himself badly. Suddenly grasping that he might be bored, they gave Pigface toys—basketballs and a floating hoop. This reduced Pigface’s self-mutilation, and he spent hours nosing and biting at the basketballs, pushing them across the water. As for the hoop, he could not only nose it, bite at it, and push it, but also chew it, shake it, pull it, kick it, and swim back and forth through it. Best of all he liked the hose the keepers used when they refilled the tank, enjoying the sensation of the water streaming over his head at exactly the right angle, and playing tug-of-war with the keeper on cleaning day by grabbing the hose and swimming backward with it, pulling it into the tank. (There is no reason to suspect that Pigface was hoping to pull his keeper into the tank, steal his keys, and make a getaway.)
Pigface’s frolicsome ways were of great interest to scientist Gordon Burghardt, since documented cases of play in reptiles are few. Burghardt speculates that Nile soft-shelled turtles like Pigface may be more inclined to play than many turtles, since they are particularly agile and speedy, and perhaps unusually good thermoregulators. Wild turtles may have to spend most of their time making a living and recovering from their exertions and so be less inclined to play, but Burghardt notes that fishermen in the eastern Mediterranean complain that Nile soft-shelled turtles destroy their fishing nets—perhaps unrecognized bouts of tug-of-war. As for Pigface, he was warm, he was well fed, no one was trying to eat him, and he had been staring at those walls for over 40 years. No wonder he was ready to play.
Pigface died at over 50 years old in 1993. His childhood is unrecorded. Whether he was already a hoop-biting, hose-grabbing, hell-raising chelonian when he was a tiny thing the size of a silver dollar is unknown.
As baby animals stagger, flutter, and splash forth into the world, mastering the basic skills, bouncing and playing, they are preparing themselves to meet new challenges, and they are learning to learn.
THREE
Learning Your Species
In the Antarctic, French explorer Jean Charcot assisted the scientists on his expedition in documenting the nests of various birds. They took a specimen egg from each nest they recorded, placing them in a basket. Charcot was delighted with the Adelie penguin colony, and amused by the way pairs stole stones from each other’s nests to enlarge their own, when they could get away with it. The advent of the explorers caused some disturbance, and Charcot noticed that one couple, who had not yet laid an egg, was taking advantage of the turmoil to rob their neighbors and improve their own nest. Charcot at once joined in, heaping up stones to make a splendid nest for the thieves, and then taking an egg from his basket and putting it in their nest ring. “Vice, once again, was rewarded in this wicked world,” wrote Charcot. “The two penguins looked at the egg in astonishment, shaking and turning it over; one of them finally decided to acknowledge ownership, and settled on it with a satisfied croak, the other made proud little crowing noises. Later, no doubt, the neighbours will all say, ‘How much he takes after you both!’”
ONE OF THE THINGS baby animals learn is so fundamental, so omnipresent, and so transparent that it can be hard to believe it is a learned thing. The baby must learn what sort of an animal it is. It’s dismaying to think you could bungle this one.
Actually, what the baby animal learns is who—and what species—its family members are. Whether it goes beyond this and assumes that it is the same kind of animal is hard to guess. Of a kitten that grew up with puppies and shares their activities people say “He thinks he’s a dog,” but does he really? Elizabeth Marshall Thomas describes a rabbit raised with dogs who joined one of them in chasing squirrels, which they never caught. “Together [they] would slowly stalk a squirrel, together they would rush it unsuccessfully, and together they would gaze up at it as it escaped into a tree.” Did the rabbit think he was a dog, or did he simply enjoy sharing the preoccupations of his friend the dog?
An orangutan named Cody was raised by humans after his mother rejected him. One day his human foster father carried him up to a cage holding an orangutan who sat placidly. Since birth Cody had never seen another orangutan, and the sight filled him with alarm. Hair on end, he scrambled behind his father, clinging so hard he left marks. The orangutan who gave him such a fright was his mother. Cody did not know he was an orangutan, but that does not necessarily mean he thought he was human. It was probably a matter he never considered.
Your mother’s name here
In the process called imprinting, a baby learns to recognize its parent or parents and perhaps its siblings. This mechanism allows a young robin to learn to associate with robins, and not ducks, or cats, or kindly wildlife rehabilitators. It happens to a greater and lesser extent and at different times in different species. Beyond imprinting, social animals learn to recognize the members of their troops or flock; territorial animals learn to know their neighbors; and animals that are vulnerable to harm from others—and that’s all animals, including skunks and King Kong—learn to spot their enemies. An otter rehabber warns that you shouldn’t let baby otters get friendly with your dogs and cats, because once released they need to beware of them. Later in life, the imprinting undergone in babyhood is often key to figuring out who would make a nice mate. And if that goes well, animals may have a chance to imprint on their own babies and learn who they are.
Imprinting has been well studied in certain species, notably waterfowl like ducks and geese. As a result it has been assumed by some that imprinting is a bird thing, but it is important in many mammals too. Do all mammals have some form of imprinting? Do we? One dictionary of animal behavior notes, “Imprinting tends to occur in those species in which attachment to parents, to the family group, and to members of the opposite sex are an important aspect of their [social organization].” That’s definitely us. Then it adds, “Imprinting seems to have evolved in those species in which there is a danger of such attachments being misplaced.” That’s not really us. Stories of children being raised by wolves are not well supported. Nor do apes snatch our children and raise them like Tarzan. We do not paddle about on lakes or graze in big herds on savannahs where our young are liable to mix with other species in a confusing way. Perhaps the primates we descended from didn’t have such a clear field, however.
An animal like a turtle, which hatches from an egg long after its mother has left, doesn’t have a chance to imprint on her, but a turtle, salmon, or eel may imprint on the taste of the water where it is born, so it can return there as an adult.
Filial imprinting
Imprinting takes place during certain times of an animal’s life, which aren’t the same for every species. These are called critical periods or sensitive periods, and often they are when the animal is very young. The classic form of imprinting is filial imprinting—imprinting on a parent or parents—and is well known to all students of cartoons. It’s the one where our hero is strolling along, spots an egg, and suddenly some little creature hatches out of it, looks into our hero’s eyes, and shrieks “Mama!” Usually when a creature finally smashes its way out of the egg, the individual beami
ng proudly really is a parent and things go without a snag.
It’s good to be able to tell your parents from other adults, since other adults might easily kill and eat you, and almost certainly don’t want to feed you and pay for your piano lessons. Why not just be born knowing what your parents should look like? Like a foundling in a Victorian novel, why not have the mental equivalent of a locket with a portrait of your parents? One answer might be that as a species evolves, what animals of that species look like (or sound like, or smell like*) may change. If we still mentally wore lockets with pictures of tree shrews (the ancestors of primates) in them, there’d be some sad scenes in maternity wards.
So the flexibility of imprinting is an obvious winner in the selection sweepstakes. Imagine two species, one of which learns who its parents are by imprinting after birth and the other of which is born knowing what its parents should look like and will accept no substitutes. The first species can evolve in ways that change its looks without difficulty. The same old script—be born, look around, that’s your mother, squawk “Mother, I’m hungry!”—will still work. But the second species won’t survive if its appearance changes, because the babies of the first generation won’t respond to them. The program for recognizing parents would have to evolve in lockstep with the changing appearance of the species, an unlikely thing.
Pioneering ethologist Konrad Lorenz found that greylag goslings “accept the first living being whom they meet as their mother, and run confidently after him.” This is one of the classic tales of imprinting. “The gosling possesses innate information that, if translated into words, would read as follows: ‘Whoever responds to your lost piping is your mother; take careful note of her appearance.’” But he was puzzled by the fact that mallard ducklings did not do this, and if the first living being they met was Lorenz, they would run away peeping desperately and hide in a corner. Yet they’d accept a big white Pekin barnyard duck as readily as a small brown mallard. Eventually Lorenz discovered that what little mallards require from a mother is constant tender quacking. He took new ducklings from an incubator, sat down in the grass with them, and quacked, saying, so he reported, “Quahg, gegegegeg, Quahg, gegegegeg.” This struck just the right note, and the adoring ducklings accepted him as their parent. Unfortunately they became hysterical if he stood up, because they didn’t recognize him that way, or if he stopped quacking for more than a moment. “The ducklings, in contrast to the greylag goslings, were most demanding and tiring charges, for, imagine a two-hour walk with such children, all the time squatting low and quacking without interruption! In the interests of science I submitted myself literally for hours on end to this ordeal,” wrote Lorenz in King Solomon’s Ring. He described his embarrassment on a day when a group of passers-by spotted him waddling and quacking in a field of grass so tall that they could not see any ducklings. However, he had achieved his goal in showing that “anything that emits the right quack note will be considered as mother, whether it is a fat white Pekin duck or a still fatter man.”
Flying lapdogs
The spectacled flying fox, a charming Australian bat, has in recent years been dreadfully afflicted by paralysis ticks. One result has been many orphaned flying foxes. Australian animal lovers rallied to adopt (and vaccinate) the babies, who cling to their mother or foster parent for the first four weeks of life. In the wild the babies, once they are too heavy to ride on their mother as she flies, are left in crèches with other baby bats. People who adopt orphans often hang them on the shower rod at this age. When they are several months old, the babies are taken to large open pens, where they can be with other bats, eat bat food, join nearby bat colonies, and leave when they feel ready. Biologist William Laurance described the heart-rending scene in an early year of bat rescue efforts, when the foster parents bravely delivered their little charges to the pens. “Though it was a wonderful scheme, it was a sad day indeed when all the moms and dads had to say goodbye to their babies as they were left, en masse, in the pens. Most of the waifs howled as they watched their tearful parents depart. Many were petrified of other flying foxes…having no idea what those other frantically screaming creatures were. Some of the babies desperately grasped little stuffed animals, the final legacy of their surrogate parents.”
I’d like to thank my family, once I figure out who they are
Many animals need to recognize their siblings. Tadpoles of the spade-foot toad sometimes turn carnivorous and eat other tadpoles. The bloodthirsty tadpole first nips the other tadpole, and if it tastes unrelated proceeds to eat it. If it is a sister or brother the tadpole eats no further. (Unless it is really really hungry.)
Incest taboos exist in many species, with animals avoiding treating their brothers and sisters as potential mates. An animal that spends a long childhood playing with its siblings should have little difficulty in recognizing them, but laboratory experiments show that some animals also seem to recognize siblings they have never met. They like to hang out with these siblings, but not to mate with them. Apparently they do it by smell. Studies of house mice showed that a mouse can smell the difference between a mouse that has similar genes coding for the major histocompatibility complex (MHC) and a mouse that has different MHC genes. A mouse in the mood for romance likes to meet another mouse whose MHC genes are different.
Many people assumed that a mouse compared its own smell with that of the other mouse. But studies in which mice were switched into unrelated litters showed that the mice grew up to treat their foster siblings as they would have treated blood siblings—as less-than-ideal mate material—and were unattracted by mice with MHC genes like those of their foster siblings. They were tragically attracted to mice with MHC genes like their own, apparently not getting the “treat her the way you would treat your own sister” or “tell him you think of him as a brother” messages they would have gotten had interfering scientists not switched them in the cradle.
Rather than compare a potential mate’s smell to its own, the mice showed what’s called familial imprinting, learning how their family members smell.
Hamsters, on the other hand, do compare their own smell to those of other hamsters, as well as noting the smell of their siblings. Researchers Jill Mateo and Robert Johnston cross-fostered hamsters, one at a time, into unrelated hamster families. When sexually mature, the female hamsters were interested in mating with mysterious strangers and not with either their foster brothers or real brothers from whom they had been separated at birth.
Learning your community
Some sheepdogs herd sheep and others live with sheep and guard them against predators. Merrily Weisbord and Kim Kachanoff describe Flintis, an Anatolian shepherd in Namibia, whose job was to chase cheetahs, jackals, hyenas, caracals, civets, and baboons away from the sheep. As soon as he had these dastards on the run he went back to the flock. He slept outside with the sheep and spent all day with them, treating them as his friends and charges and not, like a herding dog, as prey only one step removed from dinner. He was raised with the flock from six weeks old, playing with the lambs. “Flintis had imprinted on the sheep. He thought he was one of them. They were, for all intents and purposes, his family.” But when Flintis was introduced to a female dog in heat, he did not hold out for a sheep. Having spent his first six weeks with dogs, he knew he was a dog. He happened to be a dog whose community consisted of sheep.
Sexual imprinting
The extent of sexual imprinting—forming an image of a desirable mate—varies from species to species and also within species. British researchers cross-fostered lambs and kids, so that the lambs were being raised by nanny goats and the kids were being raised by ewes, but allowed the lambs to play with other lambs and the kids to play with other kids as they grew up. The lambs and kids grew up playing and grooming after the style of their foster mother, but acting like their own species in their styles of vocalizing, feeding, climbing, and fighting. When offered photographs of sheep and goat faces in a choice test, the young sheep raised by goats preferred to look at goat
portraits, and the young goats raised by sheep preferred to look at sheep portraits. (Sheep are surprisingly attentive to portraits of sheep, can distinguish the faces in them, and recognize head shots of sheep they haven’t seen for a year.) Once they were adult, the males wanted to hang out with females of their foster mother’s species. So the billy goats raised by sheep were attracted to ewes, and the rams raised by goats were attracted to nanny goats. The preferences of the cross-fostered females were weaker and faded with time. At first they preferred to hang out with animals of the same species as their foster mother, but eventually the ewes were only interested in rams and the nanny goats were only interested in billy goats. The researchers, writing in Nature, argue that the finding that males are more potently influenced by their mothers “indirectly supports Freud’s concept of the Oedipus complex and suggests that males may also be less able than females to adapt to altered social priorities.”
Wildlife rehabilitators who work with baby animals must beware of letting chicks, kits, cubs, or pups imprint on them. They also worry about two other kinds of learning, habituation and tameness. In the process of habituation, the animal merely gets used to something that might otherwise scare it. Perhaps a captive squirrel gets used to the idea that someone is going to walk past its cage carrying food dishes and stops panicking every time it happens. Or it gets used to hearing cars drive up. This might be a problem if it greets cars after it’s released.
Becoming a Tiger: The Education of an Animal Child Page 8