雅思阅读真题翻译-剑桥雅思4阅读Test1Passage2原文译文

第1段

Some of the senses that we and other terrestrial mammals take for granted are either reduced or absent in cetaceans or fail to function well in water. For example, it appears from their brain structure that toothed species are unable to smell. Baleen species, on the other hand, appear to have some related brain structures but it is not known whether these are functional. It has been speculated that, as the blowholes evolved and migrated to the top of the head, the neural pathways serving sense of smell may have been nearly all sacrificed. Similarly, although at least some cetaceans have taste buds, the nerves serving these have degenerated or are rudimentary.

第2段

The sense of touch has sometimes been described as weak too, but this view is probably mistaken. Trainers of captive dolphins and small whales often remark on their animals’ responsiveness to being touched or rubbed, and both captive and free-ranging cetacean individuals of all species (particularly adults and calves, or members of the same subgroup) appear to make frequent contact. This contact may help to maintain order within a group, and stroking or touching are part of the courtship ritual in most species. The area around the blowhole is also particularly sensitive and captive animals often object strongly to being touched there.

第3段

The sense of vision is developed to different degrees in different species. Baleen species studied at close quarters underwater – specifically a grey whale calf in captivity for a year, and free-ranging right whales and humpback whales studied and filmed off Argentina and Hawaii – have obviously tracked objects with vision underwater, and they can apparently see moderately well both in water and in air. However, the position of the eyes so restricts the field of vision in baleen whales that they probably do not have stereoscopic vision.

第4段

On the other hand, the position of the eyes in most dolphins and porpoises suggests that they have stereoscopic vision forward and downward. Eye position in freshwater dolphins, which often swim on their side or upside down while feeding, suggests that what vision they have is stereoscopic forward and upward. By comparison, the bottlenose dolphin has extremely keen vision in water. Judging from the way it watches and tracks airborne flying fish, it can apparently see fairly well through the air-water interface as well. And although preliminary experimental evidence suggests that their in-air vision is poor, the accuracy with which dolphins leap high to take small fish out of a trainer’s hand provides anecdotal evidence to the contrary.

第5段

Such variation can no doubt be explained with reference to the habitats in which individual species have developed. For example, vision is obviously more useful to species inhabiting clear open waters than to those living in turbid rivers and flooded plains. The South American boutu and Chinese beiji, for instance, appear to have very limited vision, and the Indian susus are blind, their eyes reduced to slits that probably allow them to sense only the direction and intensity of light.

第6段

Although the senses of taste and smell appear to have deteriorated, and vision in water appears to be uncertain, such weaknesses are more than compensated for by cetaceans’ well-developed acoustic sense. Most species are highly vocal, although they vary in the range of sounds they produce, and many forage for food using echolocation1. Large baleen whales primarily use the lower frequencies and are often limited in their repertoire. Notable exceptions are the nearly song-like choruses of bowhead whales in summer and the complex, haunting utterances of the humpback whales. Toothed species in general employ more of the frequency spectrum, and produce a wider variety of sounds, than baleen species (though the sperm whale apparently produces a monotonous series of high-energy clicks and little else). Some of the more complicated sounds are clearly communicative, although what role they may play in the social life and ‘culture’ of cetaceans has been more the subject of wild speculation than of solid science.

第1段

我们和其他陆地哺乳动物觉得理所应当的某些感觉在鲸类动物中或者减少或消失，或者在水中不能很好地发挥作用。例如，从它们的大脑结构看来，有齿物种无法闻到气味。须鲸物种，在另一方面，似乎有一些相关的大脑结构，但不清楚这些是否有用。据推测，随着气孔的进化并迁移到头顶，起到嗅觉作用的神经通路可能几乎全部被牺牲了。同样，尽管一些鲸类具有味蕾，但服务于它们的神经已经退化或十分原始。

第2段

有时触感也被描述为较弱，但是这种观点可能是错误的。圈养海豚和小鲸的培训师往往提到，他们的动物会对被抚摸或者摩擦做出反应。而无论是圈养还是自由放养的所有鲸类动物个体（特别是成年鲸鱼和幼崽之间，或同一亚种的成员之间）都会频繁接触。这种接触可能有助于维持群体内的秩序。在大多数物种中，抚摸或触碰是求偶仪式的一部分。气孔周围的区域也特别敏感，圈养动物经常强烈反对接触它们那里。

第3段

在不同的物种中，视觉得到了不同程度的发展。在水下近距离处研究的Baleen物种-具体来说包括被圈养一年的灰鲸幼崽，以及在阿根廷和夏威夷附近研究并拍摄的自由放养的右鲸和座头鲸-显然在水下用视觉跟踪物体，并且它们无论是在水中还是在空气中都能够看的很清楚。但是，眼睛的位置限制了鲸鱼的势力范围，以至于它们可能没有立体视觉。

第4段

另一方面，大多数海豚和鼠海豚的眼睛位置表明它们具有向前和向下的立体视觉。淡水海豚在喂食时经常侧卧或倒立游泳，其眼睛位置表明它们所具有的视觉是向前和向上立体的。相比之下，宽吻海豚在水中的视野非常敏锐。从它观察和跟踪空中飞鱼的方式来看，它显然可以通过空气与水的界面看的相当清楚。尽管初步的实验证据表明其在空气中的视力很差，但海豚飞跃起来从训练师手中取走小鱼的精准度提供了与之相反的证据。

第5段

毫无疑问，可以用个体物种的栖息地来解释这种变化。例如，视觉对于居住在开阔水域的物种显然比生活在浑浊的河流和泛滥平原中的物种更有用。例如，南美boutu 和中国beiji的视力似乎非常有限，而印度的susus则是瞎的，他们的眼睛变成狭缝，这可能使他们只能感知光的方向和强度。

第6段

虽然味觉和嗅觉会有所衰减，水中的视觉也不太确定，但这些弱点都被鲸类发达的听觉所弥补。尽管它们产生的声音范围各不相同，但大多数种类都具有很强的发声能力，并且许多动物使用回声定位法觅食。大型鲸鱼主要使用较低的频率，并且通常在其曲目方面受到限制。值得注意的例外是夏天的弓头鲸几乎像歌一样的合唱，以及座头鲸的复杂而令人难以忘怀的话语。一般而言，带齿的物种使用的频谱要多于Baleen物种（虽然，抹香鲸显然会产生一系列单调的高能滴答声，没有其他内容），因此它们会使用更多的频谱，并产生更广泛的声音。一些更复杂的声音显然具有交流目的。尽管它们在鲸类社会生活和文化中所扮演的角色更多的是推测而非实在的科学。