2021年6月17日雅思考试机经完整版(4)

2021年6月17日雅思考试机经完整版(4) 关于这个问题下面小编就来为各个考生解答下。

2021年6月17日雅思考试机经完整版(4) 

2021.06.17

READING

Passage 3

Topic

The Secret Sounds of Elephants

九分达人6 Test5 Passage3 Elephant Communication

Elephant Communication

O Connell-Rodwell, a postdoctoral fellow at Stanford University, has traveled t Namibia's first-ever wildlife reserve to explore the mystical and complicated realm of elephant communication. She, along with her colleagues, is part of a scientific revolution that started Most 20 years ago. This revolution has made a stunning revelation: elephants are capable of

| communicating with each other over long distances with low-frequeney sounds. also known as infrasounds, which are too deep for humans to hear,

As might be expected, African elephants able 10 detect seismic sound may have something to do with their cars. The hammer bone in an elephant's inner ear is proportionally huge for a mamma! but it is rather normal for animals that use vibrational signals. Thus, it may be a sign that suggests clephants can use scismic sounds to communicate.

Other aspeets of elephant anatomy also support that ability, First, their massive bodies, which enable them to give out low-frequeney sounds almost as powerful as the sound a jet makes during takeoff, serve as ideal frames for reeiving ground vibrations and transmitting them to the inne ear. Second, the elephant's toe bones ane set on a fly pad, which might be of help when focusing v ibrations from the ground into the bone. Finally, the elephant has an enormous brain that sits in the cranial cavity behind the eyes in line with the audiory canal. The front of the skull is riddled with sinus cavities, which might function as resonating chambers for ground vibrations.

It remains unclear how the elephants delect such vibrations, but OConnell-Rodwell raises a point that the pachyderms are "listening with their trunks and feet instead of their I ears.

The elephant trunk may just be the most versatile appenduge in nature. Iis uilisation encompasses drinking. bathing. smeling. feeding and scralching Both trunk and feet contain two ypes of merve endings that are sensitive 10 pressure-one detects infrasonic vibration, and another responds to vibrations higher in frequencies. As OConnell-Rodwel sees, this research has a boundless an unpredictable future. Our work is really interfaced of gcophysics, neurophysiology and ecology, she says. 'We 're raising questions that have never even been considered before.'

It has been well-known to scientists that seismic communication is widely observed among small animals, such as spiders, scorpions, insects and quite a lot of vertebrate species like white-lipped frogs, blind mole rats kangaroo rats and golden moles. Nevertheless OConnell-Rodwell first argued that a giant land animal is also sending and reeiving seismic signals, 1 used to lay a male planthopper on a stem and replay the clling sound of a female, and then the male one would exhibit the same kind of behaviour that happens in clephants- - he would freeze, then press down on  his legs, move forward a lte,t then stay stll again. I find it so fascinating, and it got me thinking that perhaps auditory communication is not the only thing that is going on.

Scientists have confirmed that 37 an elephants capacity to communicate over long distance is essential for survival, especially in places like Etosha, where more than 2, 400 savanna elephants range over a land bigger than New Jersey. It is already difficult for an elephant to find a mate in such a vast wild land, and the elephant reproductive biology only complicates it. Breeding herds also adopt low-frequency sounds to send alerts regarding predators. Even though grown-up elephants have no enemies else than human beings, baby elephants are vulnerable and are susceptible to lions and hyenas attack. At the sight of a predator, older ones in the herd will clump together to form protection before running away.

We now know that elephants can respond to warning calls in the air, but can they detect signals transmitted solely through the ground? To look into that matter, the research team designed an experiment in 2002, which used electronic devices that enabled them to give out signals through the ground at Mushara. The outcomes of our 2002 study revealed that elephants could indeed sense waming signals through the ground, 'O Connell-Rodwell observes

Last year, an experiment was set up in the hope of solving that problem. It used three different recordings- -theI 994 warning call from Mushara, an ant-predator call recorded by scientist Joyce Poole in Kenya and a made-up warble tone.“The data I've observed to this point implies that the elephants were responding the way I always expected. However, the fascinating finding is that the anti-predator call from Kenya, which is unfamiliar to them, caused them to gather around, tense up and rumble aggressively as well but they didn't always flee. I didn't expect the results to be that clear-cut.'

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