共用题干第二篇Don ’ t Count on Dung Con

共用题干

第二篇

Don ’ t Count on Dung

" Conservationists（自然保护主义者）may 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 that they
estimate animal numbers from the piles of dung（粪）the creatures leave behind.
The mistake could lead 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(WCS)in New York.
Biologist Katy Payne of Cornell University in Ithaca,New York,agrees."We really need to know ele-
phant numbers and the evidence that we have is quite indirect,"says Payne,who electronically
tracks elephants.
Counting elephants from planes is impossible in the vast rainforests of Central Africa. So researchers of-
ten estimate elephant numbers by counting dung piles in a given area.They also need to know the rate at
which dung decays.Because it’s extremely difficult to determine these rates,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（离开正道）,"says Plumptre.
He and his colleague Anthony Chifu Nchanji studied decaying elephant dung in the forests of Came-
roon.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 Plumptre."However
accurate your dung density estimate might be,the decay rate can severely affect the result."
Plumptre also says that the dung-pile census should be carried out over a region similar in size to an ele-
phant’s natural range."The usual technique of monitoring only small,protected areas distorts numbers be-
cause elephants move in and out of these regions,"he says."If the elephant population increases within the
protected area,you cannot determine whether it is a real increase or whether it is due to elephants moving in
because they are being poached（入侵偷猎）outside."
Plumptre says that similar problems may also affect other animal census studies that rely on indirect evi--
dence such as nests,tracks or burrows（地洞）.

The word"threatened"in the first sentence of the first paragraph could be best replaced by_________. A:"endangered" B:"frightened" C:"killed" D:"angered"