A kangaroo cannot jump if its tail is lifted off the ground. It needs its tail for pushing off.

According to tests made at the Institute[研究所] for the Study of Animal Problems in Washington， D.C.， dogs and cats， like people， are either right-handed or left-handed， that is， these animals favor either their right or left paws [爪子].

Migrating [遷移的] geese fly in a V formation [隊列] to save energy. A goose’s wings flutter[扇動]the air and leave an air current behind. In the flying formation， each bird is in position to get a lift from the current left by the bird ahead. It is easier going for all， except the leader. During a migration， geese usually take turns in the leading position.

An electric eel[電鰻] can produce electricity of more than 600 volts[伏]， 3 times more powerful than a household outlet. It not only uses this power to kill its prey but to locate it as well. Though it is born with eyes， it will be blind after it grows up. It finds food by its electricity in the same way as man uses radar [雷達 ].

A hummingbird’s[蜂鳥的] average weigh is less than a penny. It has a body temperature of 111 degrees and beats its wings more than 75 times a second. A newborn hummingbird is as big as a bumblebees [大黃蜂]and its nest’s size is as big as a walnut. The hummingbird is the only bird that can fly backward.

The penguin [企鵝] has a organ above its eyes that can transform salt water into fresh. The penguin has only one mate during its life and is such a conscientious [有責任心的] parent that it will， if necessary， starve[餓] to death in order to provide its children with food.

The female knot-tying weaverbird [織巢鳥]will refuse to mate with a male who has built a shoddy [劣等的] nest. If the male is refused， it must take the nest apart and completely rebuild it in order to win the affection [喜愛] of the female.

Though the giraffe’s neck is about 9 feet long， it has the same number of vertebrae[脊椎骨]as a mouse’s—seven. The giraffe’s tongue is 18 inches long. It can open and close its nostrils [鼻孔] at will. It can run faster than a horse， and makes almost no sound.

A horse focuses[聚焦] its eye by changing the angle of its head， not by changing the shape of the lens of the eye， as humans do.

It is the female lion who does more than 90 percent of the hunting while the male is afraid to risk his life， or simply prefers to rest.

There are no penguins at the North Pole. In fact， there are no penguins anywhere in the Northern Hemisphere[北半球] except in zoos. All seventeen varieties of the birds are found below the equator [赤道]， primarily in Antarctica.

Arctic terns[燕鷗] that are found in North America and the Arctic migrates each year as far south as Antarctica and back， a round trip of over 18，000 miles. This is probably the longest migration flight.

如果袋鼠的尾巴離開地面，袋鼠就跳不起來。它要靠尾巴推動才能離開地面。

華盛頓特區動物問題研究所的試驗表明，狗和貓像人一樣，也有右撇子和左撇子——即有些喜歡用右爪，有些喜歡用左爪。

遷移中的大雁群成“V”字隊形飛行是為了節省能量。一只大雁的翅膀扇動空氣，在身后留下一股氣流。在飛行隊列中，每一只大雁都得到前面的雁產生的氣流的升力。這樣，除了領隊以外，所有的雁飛起來都省力些。一次遷移飛行中往往有幾只大雁輪流領飛。

電鰻能釋放出超過600伏的電，是家用電燈電流的3倍。它不僅用這一電力殺死獵物，還用它尋找獵物。電鰻雖然出生時有眼睛，但是長大后會變成瞎子，它像人使用雷達那樣通過放電尋找食物。

蜂鳥的平均體重比一枚一便士的硬幣還輕。它的體溫達111度，翅膀每秒種要扇動75次以上。孵出的蜂鳥只有大黃蜂那么大，其巢只有核桃那么大。蜂鳥是唯一能倒退向后飛的鳥。

企鵝眼睛上邊有個器官能將鹽水變成淡水。企鵝一生中只有一個配偶，對子女很盡心，為了給孩子們找食甚至不惜自己餓死。

會打結的雌織巢鳥不肯同造窩馬馬虎虎的雄鳥交配。如果雄鳥被拒絕，它必須將巢拆掉重新造一個，以贏得雌鳥的愛情。

盡管長頸鹿的脖子約有9英尺長，但它和老鼠的頸椎骨的數目一樣，只有7塊。長頸鹿的舌頭有18英寸長。它能任意開閉鼻孔，能跑得比馬快而幾乎不發出任何聲音。

馬通過轉動頭的角度使眼鏡聚焦，不像人那樣通過改變瞳孔的形狀聚焦。

90%的食物由母獅獵取，雄獅則害怕用生命冒險或者只是喜歡休息。

北極沒有企鵝。事實上，北半球除了動物園里，任何地方都沒有企鵝。所有17種企鵝都在赤道以南，主要在南極洲。

人們發現北美洲和北極地區的北極燕鷗每年一直要遷移到南極洲再飛回來，往返行程超過18，000英里。這也許是最遠的遷移飛行。