Chausiki, a wild chimpanzee in the Mahale Mountains of Tanzania, was sick. She dozed dozed lethargically while those around her fed. Her urine was dark, her stools were loose, her back was visibly stiff, and she ignored her whimpering young son. She then sought out a little shrub, the “bitter-leaf” or “goat-killer”. Chauiki stripped away the highly toxic outer layers of its shoots. For twenty minutes she chewed and sucked the more mildly poisonous inner pith. The son tried to copy hos mother, but he spat out the bitter plant in obvious disgust. A day later, Chausiki was cured. She travelled swiftly ahead of her group, and fed as usual.
Two scientists were watching her. Mohamedi Seifu Kalunde, a Tanzanian traditional herbalist, and Michael Huffman, an American biologist. The herbalist in formed his companion that the bitter-leaf plant is a strong, broad-spectrum medicine used against malaria, schistosomiasis, amoebic dysentery and intestinal worms. Later chemical analysis showed that bitter-leaf pith contains at least ten different compounds active parasites.
Huffman and Seifu’s account of Chauskili’s cure was one of the first scientific reports of animal self-medication. Cindy Engel tells the story well in Wild Health, a wonderful collection of tales about the ways in which animals prevent and cure ill-health. A general in Han Dynasty China noticed that sick horses gained vigour from eating Plantago asiatica, and fed it with goof effect to his sick soldiers. Modern laboratory studies have found that poisoned rats turn to eating clay, and rats in pain will choose food laced with painkillers. Engel develops the argument that wild animals maximise their chances of good health when they live in rich natural environments where they ae free to direct their own behavior.
Engel is not a sentimentalist. She notes the widespread belief that wild creatures- and house cats- go off to die in stoic solitude, but points out that if an animal is sick and weak, the safest thing it can do is to hide from predators and pushy rivals of its own species. It goes off alone not to die, but to die itself the best chance of living. Similarly, she doesn’t believe that animals have a mystic ability to identify specific cures for specifically diagnosed disease. Our folk feeling that medicine has to be bitter to do any good may derive from the fact that natural cures often taste of tannins or alkaloids. A chimp with a stomach ache may seek out a broad-spectrum antidote like the bitter-leaf. Or it may swallow whole leaves from several different kinds of hairy plants: leaves with Velcro: hooks help clear out intestinal worms. Bears before hibernation and snow geese before migration also turn to Velcro plants. Domestic dogs and cats chew grass, which has the same scouring effect. Many wild animals, and some people, develop ”pica” when ill, a craving to eat earth-particularly clay, which assuages diarrhea and binds to many poisons. Among the most famous clay-eaters are the parrots of the Amazon. Scarlet macaws, blue and gold macaws, and hosts of smaller birds perch together in their hundreds to excavate the best clay layer along a riverbank. Parrots’ regular diet is tree seeds, which the defend with toxic chemicals, and clay is an essential buffer to the toxins.
Plants and animals have evolved myriad strategies for defending themselves against the continuous onslaught. Those that cannot do so efficiently become extinct. Animals have coherent, self-repairing skin, closing, mucus-lined orifices, complex immune systems, and behavioural dodges to avoid being eaten alive. Plants have bark and hairs and, above all, toxins. Fungal toxins range from antibiotics that repel and kill predatory bacteria, to poisons strong enough to kill off mushroom-collecting gourmets. No surprise, then, that small doses of some of these bio-active substances are effective as medicines. If plants use them against their own micro and macro-parasites, animals can borrow the effects to medicate themselves.
Engel’s suggestion is that we would have much to gain from studying animals’ health-related behavior. Animals occasionally indulge in recreational drugs-they get drunk, sedate themselves into a stupor, and eagerly consume stimulants. Nature’s pharmacy provides many intoxicants. They work by mimicking the action of neurological chemicals, and plants produce them because they defend against herbivorous predators. Getting high ought to reduce an animal’s adaptive fitness, falling out of trees and stumbling away from predators is not the best way to get our genes into the next generation. · One. proposed explanation is that animal alcoholics are after the high ca calorie nourishment of ethanol.
A better theory.is that drugs area short circuit to the .pleasure centres. Pleasure is usually a reward for behaviour patterns that are good for survival and reproduction. By taking a psychoactive drug, animals (and people] skip the hard work of getting food , and getting resources or getting laid, and get the pleasure pay-off directly. Because psychoactive chemicals are rare in the wild and come in small doses, the casually rate in spaced-out animals hasn’t been high enough for it to be a factor in selection. Human technology has given us artificially purified drugs often attractively packaged and marketed for anyone who wants them.’ The social brake .of legislation seems powerless against the unhealthy combination of natural desire and technological know-how," Engel remarks, ruefully.
Animals, don’t always do the healthy thing. There are wild bears in the Yosemite National Park that scavenge waste dumps and become obese, often twice their normal weight Baboons, too, jump (or rather don’t at the opportunity to become couch potatoes‘In the Serengeti reserve they can lie about all· morning till the waster trucks from the hotels arrive, binge on high-sugar, high-fat, high-protein leftovers，and relax au afternoon. Over the years the baboons have got fatter, reached puberty earlier and acquired higher levels of cholesterol and insulin, The lesson is, of course, that when an animal is removed from the environment in which it evolved, drives and desires that were once adaptive can become highly ;'maladaptive-a lesson it has taken 'people a Jong time to understand.
Do the following statements agree with the information given in the Reαding Passage? In boxes 1 10 on your answer sheet, write YES NO NOT GIVEN
if the statement agrees with the claims of the writer.
if the statement contradicts the claims of the writer
if it is impossible to say what the writer thinks αbout this
1 Two scientists observed that a female chimpanzee taught her son how to use the bitter-leaf to cure stomach ache.
2 In ancient China, horses found Plantago asiatica and fed sick soldiers.
3 When sick or weak, some wild animals depart from the group in order to survive
4 According to our folk feeling, the bitter the medicine tastes, the better healing effect it has.
5 Dogs and cats eat grass to clean their intestines.
6 Parrots eat clay because it helps them digest tree seeds.
7 Toxin is one of the plants’ self-defense mechanisms against their natural enemies.
8 Animals sometimes prefer recreational drugs which in fact shorten the odds of
9 Wild bears occasionally take psychoactive drugs to get pleasure.
9 People should not always keep animals in zoos.