剑桥雅思9听力真题原文:Test1—section4(2)

2022-05-27 08:13:09

  

  Althernatively,it has also been suggested that someanimals strand accidentally by following their preyashore in the confusion of the chase.I 1995 DavidThurston monitored pilot whales that beached afterfollowing squid ashore.However,this idea does notseem to hold true for the majority of massstrandings because examination of the animals'stomach contents reveal that most had not beenfeeding as they stranded.

  There are also some new theories which link strandings to huamns.A growing concern is thatloud noises in the ocean cause strandings.Noises such as those caused by military exercisesare of particular concern and have been pinpointed as the cause of some strandings of late.

  One of these,a mass stranding of whales in 2000 in the Bahamas coincided closely withexperiments using a new submarine detection system.There were several factors that madethis stranding stand out as different from previous strandings.This led researchers to look fora new cause.For one,all the stranded animals were healthy.In addition,the animals were spreadout along 38 kilometres of coast,whereas it's more common for the animals to be found in agroup when mass strandings occur.

  A final theory is related to group behaviour,and suggests that sea mammals cannotdistinguish between sick and healthy leaders and will follow sick leaders,even to an inevitabledeath.This is a particularly interesting theory since the whales that are thought to be mostsocial - the toothed whales - are the group that strand the most frequently.

  The theory is also supported by evidence from a dolphin stranding in 1994.Examination of thedead animals revealed that apart from the leader,all the others had been healthy at the time oftheir death.

  Without one consistent theory however it is very hard for us to do anything about thisphenomenon except to assist animals where and when we can.Stranding networks have beenestablished around the world to aid in rescuing animals and collecting samples from those thatcould not be helped.I recommend John Connor's Marine Mammals Ashore as an excellentstarting point if you're interested in finding out more about these networks,or establishing oneyourself.

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