第20章 马

家马和野马的通称。化石证据表明，马科动物最早起源于北美。最早的马祖先化石在密西西比河流域始新世地层中发现，被称为始祖马。家马约于4500年前被人类驯化，品种繁多。

马和人有着特殊的关系，是人类的伙伴和朋友，可以为人们的农耕、运输、游猎、畜牧、探险、娱乐、运动等活动服务。马粪可用来培养蘑菇，破伤风抗毒素是用马的血清制成。

家马可分三种类型：挽马，四肢粗大，体高2米左右；小型马，体高144厘米以下；轻型马。

马的神经系统高度发达。具有复杂的本能，记忆力和判断力强。马的方向感觉极为发达，因此，可以找到回家的路。由于视觉记忆，再次遇到早先使它害怕的地点或事物时，它就会惊退。由于听觉记忆，人们可用各种口令来训练它们。

马的寿命一般20年，最长可达30多年。3岁性成熟，5岁成年。母马怀孕11个月，通常产一仔，偶产2仔。小马6个月时断奶。

野马数量极少。国际自然和自然资源保护联盟所编纂的红皮书将它列为濒危物种，中国已将它划为保护动物。

Horses are speedy and graceful animals.You’ll know this if you’ve ever watched a horse race.When a horse runs，it can have all four of its feet in the air at the same time.A photographer demonstrated this surprising fact with photographs in 1887.

In the past，people rode horses when they wanted to get somewhere fast.Horses also helped people by pulling plows，loaded wagons，and other heavy farm equipment.

Horses are large land mammals that can run fast for long distances.They are social animals，forming strong bonds with other horses and with humans.For thousands of years，humans have used horses for transportation and farming.Today，horses are used mostly for pleasure and sport，as in the horsemanship competition pictured here.

When a horse runs，it can have all four of its feet in the air at the same time.In 1887，photographer Edweard Muybridge captured a horse in motion in Jockey on a Galloping Horse.

A female horse，or mare，usually gives birth to a single foal.The foal relies on its mother’s milk for nourishment.

The Royal Canadian Mounted Police，known as Mounties，used horses to patrol remote areas in the late 1800s.Today，the Mounties use horses mainly for parades and public appearances

In the sport of polo，players ride horses and use a mallet to try to hit a ball into a goal.Polo horses are well trained.From a gallop，they can stop and turn quickly.

What Are Horses Like？