蝙蝠的5个惊人事实。 Sally's English Class（第8期）
Sally的线下课在跟孩子们讲述蝙蝠，看看蝙蝠不为人知的这些秘密吧。
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5 Surprising Facts About Bats
蝙蝠的5个惊人事实
There Are More Than 1,200 Species of Bats.
蝙蝠的种类超过了1200种
Bats are usually divided into two suborders: Megachiroptera (large Old World fruit bats) and Microchiroptera (small bats found worldwide). They range in size from the giant flying foxes, with wingspans up to 5 feet (1.5 meters), to the itty-bitty bumblebee bat, with only a 6-inch (15-cm) wingspan. There are even three different species of blood-drinking vampire bats.
蝙蝠通常分为两个亚目：巨翼手目（旧大陆大型果蝠）和微型广翅目（世界各地都有的小型蝙蝠）。它们的体型从翼展高达5英尺（1.5米）的巨型飞狐到翼展只有6英寸（15厘米）的小黄蜂蝙蝠。甚至还有三种不同种类的吸血蝙蝠。
Bats Are the Only Mammals Capable of Flight.
蝙蝠是唯一会飞的哺乳动物
Like all true mammals, baby bats are nourished with milk from their mothers. Bats bear live young—usually only one, although some species can have up to three or four at a time. But no other mammal can fly like a bat can. “Flying” squirrels and similar mammals can only glide at best. In order to make flight possible, bats digest their food extremely fast, sometimes excreting within 30 to 60 minutes of eating. That helps them keep their weight down.
像所有真正的哺乳动物一样，蝙蝠宝宝是用妈妈的奶喂养的。蝙蝠通常只生一只幼蝙蝠，但有些种类的蝙蝠一次最多能生三到四只。但是没有其他哺乳动物能像蝙蝠一样飞翔。“会飞”的松鼠和类似的哺乳动物充其量只能滑翔。为了能够飞行，蝙蝠对食物的消化速度极快，有时在进食后30至60分钟内就排便。这有助于他们减轻体重。
Bat Droppings Can Be Used to Make Gunpowder.
蝙蝠的粪便可以制造火药
Speaking of bat droppings, also known as guano, they are high in potassium nitrate (saltpeter) and are often used as fertilizer. The saltpeter can also be extracted for use in gunpowder and explosives, and bat guano was an important resource for that purpose during the American Civil War. Bat guano has also been found to preserve fossils.
说到蝙蝠粪便，也有称为鸟粪的，它们富含硝酸钾（硝石），常被用作肥料。硝石也可以被提取用于火药和炸药，而蝙蝠粪因此在美国内战期间成为一种重要的资源。蝙蝠粪也被发现用来保存化石。
Not All Bats Hang Upside Down.
并不是所有蝙蝠都头朝下悬挂
Almost all bat species hang upside down. Their feet have evolved to be relaxed in a clenched position (difficult for a human to imagine). When they’re ready to fly, they let go and gain momentum from falling, since their little legs and wings can’t give them the kind of lift birds get. However, there are six species of bats that don’t hang upside down. Most of these bats have suctioning pads on their limbs that let them stick to leaves or other surfaces.
几乎所有的蝙蝠都倒倒挂着。他们的脚已经进化到可以在紧握的姿势下放松（人类很难想象）。当它们准备好飞翔时，它们会松开，从坠落中获得动力，因为它们的小腿和小翅膀无法给它们提供鸟类所能获得的升力。然而，有六种蝙蝠不会倒挂。它们的四肢上都有吸盘，可以让它们粘在树叶或其他表面上。
Bats Aren’t Really Blind.
Only the smaller species of bats use echolocation as their main means of orienting themselves. Bigger bats can see better than humans. Sight is a blessing and a curse, however, because sight can override echolocation signals. For instance, a bat may fly into a window because it sees light outside, even if echolocation tells it the surface is solid.
只有较小种类的蝙蝠使用回声定位作为他们自己定向的主要手段。大蝙蝠比人类看得都清楚。视力是福也是祸，因为视力可以否决回声定位信号。例如，蝙蝠可能会飞撞上玻璃窗，因为它能看到外面的光线，即使回声定位告诉它窗户有固体表面。
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