IELTS READING – TABLE COMPLETION – TEST 3

Health In The Wild

Many animals seem able to treat their illnesses themselves. Humans may have a thingor 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  scepticism  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.

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  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.

Other  observations  also  support  the  idea  that  clay  is  detoxifying.  Towards  the tropics the amount of toxic compounds in plants increases-and so does the amount of  earth  eaten  by  herbivores.  Elephants  lick  clay  from  mud  holes  all  year  round, except in September when they are bingeing on fruit which, because it has evolved to  be  eaten,  is  not  toxic.  And  the  addition  of  clay  to  the  diets  of  domestic  cattle increases the amount of nutrients that they can absorb from their food by 10-20%.

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.  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 live-stock. 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.

Questions 1-5

Complete the notes below using NO MORE THAN ONE WORD OR NUMBER  from the passage