虽然两国人民未经许可不能越过边境，但动物可以自由跨过边境。
Though people of two countries cannot go across the border without permission, animals, however, can cross the border freely.
两只动物严肃地点头。
这两只动物伏在地上，低头下拜。
The two animals, crouching to the earth, bowed their heads and did worship.
两只动物面面相觑，哈哈大笑。
两只动物站起来，小心地互相打量着。
“我确定我很荣幸。”水獭说，两只动物立刻成了朋友。
"Proud, I'm sure," said the Otter, and the two animals were friends forthwith.
獾子班杰踏着重重的步子走进屋里，站在那儿，一脸严肃地望着那两只动物。
The Badger strode heavily into the room, and stood looking at the two animals with an expression full of seriousness.
他把两只动物领到一个长长的房间里，这个房间一半像卧室，一半像阁楼。
He conducted the two animals to a long room that seemed half bedchamber and half loft.
这两个小动物看上去一点也不害怕玛丽。
Neither of the creatures looked as if he were the least afraid of Mary.
对他来说，它也是一个鼻子，因为它的末端有一个类似杯子的空缺，杯子的底部有两个洞，动物可以通过它们来嗅闻和呼吸。
It is also a nose to him, for at the end of it there is a empty place like a cup, and in the bottom of the cup are two holes, and the animal smells and breathes through them.
但现在，如果动物在两个合适的栖息地之间表现出明确的选择呢？
But now, what about cases where an animal exhibits a clear choice between two suitable habitats?
动物们一如往常分两派。
同样一段距离，企鹅以其摇摆的方式来行走，所消耗掉的体能是其他同体型动物的两倍之多。
To waddle a given distance, penguins use twice as much energy as other creatures of the same size use to walk equally far.
将不同的工作分配给不同的大脑半球，可能对鸟类或鱼类等动物特别有利，因为它们的眼睛长在头部两侧。
Assigning different jobs to different brain halves may be especially advantageous for animals such as birds or fish, whose eyes are placed on the sides of their heads.
这种说法从一开始就将讨论引向两个极端，它使人们认为应这样对待动物：要么像对人类自身一样关切体谅，要么完全冷漠无情。
It leads the discussion to extremes at the outset: it invites you to think that animals should be treated either with the consideration humans extend to other humans, or with no consideration at a1l.
这张照片里，位于新加坡动物园才两周大的环尾狐猴紧紧的贴在它妈妈的身上。
In this photo, a two-week-old ring-tailed lemur clings on to its mother at the Singapore Zoo.
动物也必须适应沙漠环境，它们可能通过两种形式的行为适应来做到这一点：它们要么逃跑，要么撤退。
Animals also have to adapt to desert conditions, and they may do it through two forms of behavioral adaptation: they either escape or retreat.
首先，擦痕上的化学物质提供了动物的个体特征信息；没有两种哺乳动物会产生相同的气味。
First, the chemicals deposited on the rub provide information on the individual identity of an animal; no two mammals produce the same scent.
艾米的爸爸在动物园里照看两只大象。
产生这种循环的因素有两个：食用植物和食肉动物。
Two factors appear to be generating the cycle: food plants and predators.
转移行为的发生是因为动物有两种相互冲突的驱动力——两种相互矛盾的冲动，在这种情况下，就是恐惧和饥饿。
Displacement occurs because the animal's got two conflicting drives—two competing urges, in this case, fear and hunger.
鸭嘴兽（Ornithorhynchusanatinus）是仅有的两种卵生的哺乳动物之一，另一种为食蚁兽（spiny anteater），它产卵。
The platypus (Ornithorhynchus anatinus) is one of only two mammals, the other is the echidna (spiny anteater) that lays eggs.
北极熊是陆地上最大的肉食性动物，比西伯利亚虎都要大两倍多！
The polar bear is the largest terrestrial carnivore, being more than twice as big as the Siberian Tiger!
近一个世纪前，生物学家发现，如果他们在无脊椎动物胚胎生命的早期阶段将其分成两部分，它会存活下来并发育成两个正常的胚胎。
Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos.
其他三种动物的区别在于它们食用的低处枝叶和高处茎杆的比例不同：斑马吃茎杆最多，角马吃叶子最多，而转角牛羚则介于两者之间。
The other three species differ in the proportion of lower leaves and higher stems that they eat: zebras eat the most stem matter, wildebeests eat the most leaves, and topi are intermediate.
例如，四趾的始祖鸟先于三趾的始祖鸟出现，但北美的化石证据表明，这两种动物之间有一个急促而不均衡的转换过程。
The four-toed Eohippus preceded the three-toed Miohippus, for example, but North American fossil evidence suggests a jerky, uneven transition between the two.
现在，更新世野生动物保护的倡导者提出了两个主要目标。
Now, the advocates of Pleistocene rewilding cite two main goals.
一种掠食动物经常大量捕食单单一种猎物时，这两个物种是紧密联系的。
When a predator always eats huge numbers of a single prey, the two species are strongly linked.
击中奥克弗诺基国家野生动物保护区深处的蜜糖大草原的闪电，可能只会撂倒两三棵树而已。
The bolt that struck Honey Prairie, deep inside the Okefenokee National Wildlife Refuge, might have just knocked down a tree or two.
翼龙是第一批会飞的脊椎动物，它的化石遗迹已经吸引了古生物学家两个多世纪。
The fossil remains of the first flying vertebrates, the pterosaurs, have intrigued paleontologists for more than two centuries.
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