动物移徙 -- -- 高级

The Great Migration happens every year. Why?
::大移民每年都会发生,为什么?

Each year, around 1.5 million wildebeest and 300,000 zebra (along with other antelope) gather up their young and start their long trek north from Tanzania's Serengeti Plains to Kenya's Masai Mara National Reserve. They go in search of food and . Their migration runs in a clockwise circle and the cover a distance of around 1800 miles. It's a tough journey, and every year an estimated 250,000 wildebeest don't survive.
::每年大约有150万只野羊和30万只斑马(与其他羚羊一起)聚集他们的年轻人,从坦桑尼亚的Serengeti平原到肯尼亚的Masai Mara国家保留地向北长途跋涉。他们去寻找食物。他们的迁徙环绕时钟,覆盖距离约1800英里。这是一个艰难的旅程,每年估计有25万只野生动物无法生存。

Migration
::移徙移徙移徙

In addition to reproductive cycles, animals have other behaviors that occur in regular cycles. One type of is migration. Other cyclic behaviors are called .
::除了生殖周期外,动物还有其他在正常周期中发生的行为。一种是移徙。其他循环行为被称为“循环行为 ” 。

Migration usually refers to seasonal movements of animals from one area to another, typically over long distances. One area is often a breeding site. Migration occurs mainly in , , , and some ocean organisms , including whales. Migration is an , but it generally occurs in response to predictable changes in the environment. For example, in the northern zone, bald eagles, which prey on fish, migrate south when ponds and lakes freeze over in the winter.
::迁徙通常是指动物从一个地区到另一个地区的季节性迁徙,通常长途迁徙,一个地区往往是繁殖地,移徙主要发生在......,以及一些海洋生物,包括鲸鱼。迁徙是一种迁徙,但一般是因环境的可预见变化而发生的。例如,在北部地区,秃鹰捕食鱼,当冬季池塘和湖泊冻结时向南迁徙。

Many other birds also migrate to milder climates from areas with harsh winters, where little food is available. Some travel incredible distances during these migrations. Figure shows migration routes of birds called bar-tailed godwits. These birds make both the longest nonstop flights of any bird and the longest journeys without food of any animal. Their migration routes are almost entirely over the Pacific Ocean. The birds fly from the or other areas in the far North (where they breed) to New Zealand or even farther south. They have been known to travel more than 11,000 kilometers (over 6,800 miles) in just nine days. How fast, on average, do they fly to cover this much distance in this amount of time?
::其它许多鸟类也从冬季严寒的地区迁移到温和的气候,那里几乎没有食物。有些鸟类在迁徙期间旅行的距离令人难以置信。图中显示了鸟类的迁徙路线,称为巴尾干虫。这些鸟类是任何鸟类最长时间的无间歇飞行,也是没有动物食物的最长旅程。它们的迁徙路线几乎完全跨过太平洋。鸟类从远北地区或其它地区飞到新西兰(他们在那里繁殖),甚至更远的南部。他们已知在短短9天的时间内行走超过11 000公里(超过6 800英里 英里 ) 。平均而言,它们飞到这么远的距离的飞行速度有多快?

Some species of whales migrate seasonally as well. Gray whales have the longest known migration route of any whale or other mammal . In the summer, one group of gray whales lives in the Bering Sea near Alaska. Beginning in October, these whales head south, traveling along the western coast of both Canada and the United States. By mid-December, they can be seen off the California coast between Monterey and San Diego. By late December, the whales begin arriving at their destination: the warm waters near Mexico’s Baja Peninsula. The entire trip covers about 10,000 kilometers (6,000 miles). The whales travel day and night and average almost 130 kilometers (80 miles) per day. Once they arrive at their destination, pregnant females give birth, and females that are not pregnant seek males for mating .
::某些鲸鱼也季节性地迁徙。 灰鲸是任何鲸鱼或其他哺乳动物迁移路线最长的已知路线。 夏季,一群灰鲸生活在阿拉斯加附近的白令海。 从10月开始,这些鲸鱼向南走,沿加拿大和美国的西海岸航行。到12月中旬,在蒙特里和圣地亚哥之间的加利福尼亚海岸附近可以看到它们。 到12月底,鲸鱼开始到达目的地:墨西哥半岛附近的温暖水域。整个旅程覆盖了大约1万公里(6,000英里 ) 。 鲸鱼日夜行,平均每天行走近130公里(80英里 ) 。 到达目的地后,怀孕女性分娩,没有怀孕的女性寻找男性交配。

Migrating to and from areas that are thousands of kilometers apart requires several abilities. Animals must be able to determine their current location, the location of their destination, and how to get from one location to the other. Many species of migratory birds determine the direction in which to fly based on cues such as Earth’s magnetic lines, the position of the sun, or the direction of prevailing winds. In addition to determining the correct direction, they must know how far or how long to travel in that direction. Other species of birds follow landmarks on Earth’s surface, such as rivers, coastlines, or mountain ridges.
::迁移到相距数千公里的地区需要几种能力。 动物必须能够确定它们目前的位置、目的地和从一个地点到另一个地点的方式。 许多候鸟物种根据地球磁线、太阳位置或风向等信号决定飞行方向。 除了确定正确的方向外,它们还必须知道向这个方向行走多远或多长。 其他鸟类种类也遵循地球表面的里程碑,如河流、海岸线或山脊。

Summary
::摘要

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• Migration occurs mainly in birds, fish, insects, and some ocean organisms, including whales.
  ::移徙主要发生在鸟类、鱼类、昆虫和一些海洋生物,包括鲸鱼。
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• Migration is an innate behavior, but it generally occurs in response to predictable changes in the environment.
  ::移徙是一种先天行为,但移徙一般是因环境的可预见变化而发生的。
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• Migrating to and from areas that are thousands of kilometers apart requires several abilities, including the ability to determine one's current location, the location of one's destination, and how to get from one location to the other.
  ::向相距数千公里的地区迁移和从这些地区迁移需要几种能力,包括确定一个人目前位置的能力、目的地的位置以及从一个地点到另一个地点的方式。

Review
::回顾

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1. What are some common reasons for animal migration?
   ::动物移徙的常见原因是什么?
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2. What animal takes the longest journey without food? What is the farthest mammalian migration?
   ::没有食物,哪种动物走得最长?最远的哺乳动物迁徙是什么呢?
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3. How do migratory birds manage to determine their direction and how long they have traveled?
   ::移栖鸟类如何设法确定其方向和行走时间?