Conservationistsmay be miscalculating the numbers of the threatened animals such as elephants.say African and American researchers.The error occurs because of a flaw in the way they estimate animal numbers from the piles of dungthe creatures leave behind.
The mistake could 1ead researchers to think that there are twice as many elephants as there really are in some regions according to Andrew Plumptre of the Wildlife Conservation Society in New York
Biologist Katy Payne of Cornell University in Ithaca，New York，agrees.We really need to know elephant numbers and the evidence that we have is quite indirectsays Payne，who electronically tracks elephants
Counting elephants from planes is impossible in the vast rainforests of Central Africa.So researchers often estimate elephant numbers by counting dung piles in a given area.They also need to know the rate at which dung decays Because its extremely difficult to determine these rates.however，researchers counting elephants in one region tend to rely on standard decay rates established elsewhere
But researchers at the WCS have found that this decay rate varies from region to region depending on the climate and environment Using the wrong values can lead the census astray，says Plumptre
He and his colleague Anthony Chifu Nchanji studied decaying elephant dung in the forests of Cameroon They found that the dung decayed between 55 and 65 per cent more slowly than the dung in the rainforests of neighbouring Gabon.If researchers use decay rates from Gabon to count elephants in Cameroon，they would probably find more elephants than are actually around.This could mean estimates in Cameroon are at least twice as high as those derived from decay rates calculated locally，says PlumptreHowever accurate your dung density estimate might be.the decay rate can severely affect the result
Plumptre also says that the dungpile census should be carried out over a region similar in size to an elephants natural range The usual technique of monitoring only small，protected areas distorts numbers because elephants move in and out of these regions，he saysIf the elephant population increases within the protected area，you can not determine whether 1t is a real increase or whether it is due to elephants moving in because they are being poachedoutside.
Plumptre says that similar problems may also affect other animal census studies that rely on indirect evidence such as nests，tracks or burrows
1The wordthreatenedin the first sentence of the first paragraph could be best replaced by
A endangered
B frightened
C killed
D angered
2 Why do researchers estimate elephant numbers in an area by counting dung piles?
A Because elephants are difficult to catch
B Because it is not possible to count elephants from a plane.
C Because it is not possible to keep track of elephants.
D Because elephants are shy animals
3 Piles of dung cant be relied upon when it comes to estimating elephant numbers because
A they are different in size
B they scatter an over the region.
C they are different in decay rate.
D they are different in quality.
4 According to Plumptre，the region over which a dungpile census is carried out should be
A small enough
B well protected.
C carefully monitored.
D large enough
5The first wordHein paragraph 6 refers to
A Andrew Plumptre
B Katy Payne.
C Anthony Chifu Nchanji.
D the writer of the article.
参考答案
1 A 2 B 3 c 4 D 5 A