Many animals seem able to treat their
illnesses themselves. Humans may have a thing or two to learn from
them. For the past decade Dr. Engel, a lecturer in
environmental sciences at Britain's Open University, has been collating examples
of self-medicating behaviour in wild animals. She recently published a book on
the subject. In a talk at the Edinburgh Science Festival earlier this month, she
explained that the idea that animals can treat themselves has been regarded with
some skepticism by her colleagues in the past. But a growing number of animal
behaviourists now think that wild animals can and do deal with their own medical
needs. William Karesh, of the Wildlife Conservation Society, in
New York, for example, has studied the health of a wide range of wild animals,
including anaconda snakes, macaws, penguins, guanacos (South American beasts
related to camels), impala and buffalo. The animals were mostly in good physical
condition, which is not surprising, since the weak quickly go to the wall in the
wild. But blood tests showed that many had encountered nasty viral and bacterial
diseases in the past—including diseases that are often fatal in captive animals,
even when treated by vets. Moreover, if healthy wild animals are brought into
captivity, their health often deteriorates unless great care is taken over their
living conditions. Such observations suggest that wild animals can do something
to keep themselves healthy that captive animals cannot. Hearty animals One example of self-medication
was discovered in 1987. Michael Huffman and Mohamedi Seifu, working in the
Mahale Mountains National Park in Tanzania, noticed that local chimpanzees
suffering from intestinal worms would dose themselves with the pith of a plant
called Veronia. This plant produces poisonous chemicals called terpenes. Its
pith contains a strong enough concentration to kill gut parasites, but not so
strong as to kill chimps (nor people, for that matter; locals use the pith for
the same purpose). Given that the plant is known locally as 'goat-killer',
however, it seems that not all animals are as smart as chimps and humans. Some
consume it indiscriminately, and succumb. Since the
Veronia—eating chimps were discovered, more evidence has emerged suggesting that
animals often eat things for medical rather than nutritional reasons. Many
species, for example, consume dirt—a behaviour known as geophagy. Historically,
the preferred explanation was that soil supplies minerals such as salt. But
geophagy occurs in areas where the earth is not a useful source of minerals, and
also in places where minerals can be more easily obtained from certain plants
that are known to be rich in them. Clearly, the animals must be getting
something else out of eating earth. The current belief is that
soil—and particularly the clay in it—helps to detoxify the defensive poisons
that some plants produce in an attempt to prevent themselves from being eaten.
Evidence for the detoxifying nature of clay came in 1999, from an experiment
carried out on macaws by James Gilardi and his colleagues at the University of
California, Davis. Macaws eat seeds containing alkaloids, a
group of chemicals that has some notoriously toxic members, such as strychnine.
In the wild, the birds are frequently seen perched on eroding riverbanks eating
clay. Dr. Gilardi fed one group of macaws a mixture of a harmless alkaloid and
clay, and a second group just the alkaloid. Several hours later, the macaws that
had eaten the clay had 60% less alkaloid in their bloodstreams than those that
had not, suggesting that the hypothesis is correct. Rough and ready A third instance of animal
self-medication is the use of mechanical scours to get rid of gut parasites. In
1972 Richard Wrangham, a researcher at the Gombe Stream Reserve in Tanzania,
noticed that chimpanzees were eating the leaves of a tree called Aspilia. The
chimps chose the leaves carefully by testing them in their mouths. Having chosen
a leaf, a chimp would fold it into a fan and swallow it. Some of the chimps were
noticed wrinkling their noses as they swallowed these leaves, suggesting the
experience was unpleasant. Later, undigested leaves were found on the forest
floor. Dr. Wrangham rightly guessed that the leaves had a
medicinal purpose—this was, indeed, one of the earliest interpretations of a
behaviour pattern as self-medication. However, he guessed wrong about what the
mechanism was. His (and everybody else's) assumption was that Aspilia contained
a drug, and this sparked more than two decades of phytochemical research to try
to find out what chemical the chimps were after. But by the 1990s, chimps across
Africa had been seen swallowing the leaves of 19 different species that seemed
to have few suitable chemicals in common. The drug hypothesis was looking more
and more dubious. It was Dr. Huffman who got to the bottom of
the problem in 1999. He did so by watching what came out of the chimps, rather
than concentrating on what went in. He found that the egested leaves were full
of intestinal worms. The factor common to all 19 species of leaves swallowed by
the chimps was that they were covered with microscopic hooks. These caught the
worms and dragged them from their lodgings. Following that
observation, Dr. Engel is now particularly excited about how knowledge of the
way that animals look after themselves could be used to improve the health of
livestock. People might also be able to learn a thing or two—and may, indeed,
already have done so. Geophagy, for example, is a common behaviour in many parts
of the world. The medical stalls in African markets frequently sell tablets made
of different sorts of clays, appropriate to different medical conditions.
Africans brought to the Americas as slaves continued this tradition, which gave
their owners one more excuse to affect to despise them. Yet, as Dr. Engel points
out, Rwandan mountain gorillas eat a type of clay rather similar to
kaolinite—the main ingredient of many patent medicines sold over the counter in
the West for digestive complaints. Dirt can sometimes be good for you, and to be
'as sick as a parrot' may, after all, be a state to be desired.
{{B}}—Economist{{/B}}
填空题
Complete the table below. Choose NO MORE
THAN TWO WORDS from Reading Passage 2 for each answer.
Write your answer in boxes on your answer sheet.
{{B}}Three Researches of Animal
Self-Medication{{/B}}
Time
Researcher
Location
Description
1987
Michael Huffman and Mohamedi Seifu
{{U}}{{U}} 14 {{/U}}{{/U}}
They found that local chimpanzees always took a
pith of {{U}}{{U}} 15 {{/U}}{{/U}}, which is also called {{U}}{{U}}
16 {{/U}}{{/U}}in local areas due to the poisonous chemicals—{{U}} {{U}}
17 {{/U}}{{/U}}in it.
1999
James Gilardi and his colleagues
{{U}}{{U}} 18 {{/U}}{{/U}}
They carried out some experiments on macaws and
found that macaws use {{U}}{{U}} 19 {{/U}}{{/U}}in soil to detoxify the
toxic chemical—{{U}} {{U}} 20 {{/U}}{{/U}}in the seeds.
From 1972 to 1999
Richard Wrangham
Tanzania
Wrangham was curious about the reason
why chimpanzees ate the leaves of {{U}}{{U}} 21
{{/U}}{{/U}}so carefully. After his drug hypothesis failed, Dr. Huffman
noticed that chimps always chose leaves with {{U}}{{U}} 22
{{/U}}{{/U}}because these kind of leaves can help drag {{U}}{{U}} 23
{{/U}}{{/U}}out.
填空题
Do the following statements agree with the information given in Reading Passage 2?
In boxes on your answer sheet, write
TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
No one now criticises the idea that animals can deal with their own medical problems.
填空题
Captive animals know how to take care of themselves as wild ones.
填空题
Human beings have already known how to use clay in medicines as animals do.