Mahatee 海牛

Juno

海牛是一种温顺、行动缓慢的生物。据考证，海牛原是陆地上的“居民”，是大象的遠亲。

The manatee is a large marine 1）mammal. Manatees are also known as sea cowsdue to their slow， 2）lolling nature and their grassy meals. However， despite the name，they are more closely related to elephants. Manatees and elephants evolved from thesame ancestor over 50 million years ago.

There are three species of manatee， 3）distinguished primarily by where they live.The West Indian manatee ranges along the North American east coast from Floridato Brazil. The Amazonian manatee species inhabit the Amazon River and the Africanmanatee swims along the west coast and rivers of Africa. Manatees range in sizefrom 2.4 to 4 meters and can weigh 200 to 590 kilograms. Though they may seem like4）cumbersome creatures， manatees can swim quickly and gracefully. Manatees usuallyswim about 8 km/h， but they can swim up to 24 km/h in short bursts when they feel aneed for speed.

Like whales and dolphins， manatees breathe air. Theygo to the surface for a gulp of air every three to five minutes.However， they can hold their breath underwaterfor up to 20 minutes. This may have to do withthe size of their lungs， as they run much of thelength of the manatee's body.

Manatees have been under attack by humansfor a long time， threatened by fishing nets， boat5）collisions， and 6）coastal development. TheIUCN's Red List of Threatened Species lists allmanatees as vulnerable or endangered and facinga high risk of extinction.

海牛是一种大型海洋哺乳动物。海牛由于行动缓慢、懒洋洋的天性和以海草为主的饥食，也被称为海里的牛。然而，尽管它们名字与牛有关，但其实它们与大象的关系更为密切。海牛和大象是从5000多万年前的同一祖先进化而来的。

海牛有三种，主要以它们居住的地方为界。西印度海牛分布在佛罗里达州到巴西的北美东海岸。亚马逊海牛栖息在亚马逊河中，非洲海牛栖息于西海岸和非洲河流。海牛体型长达2.4～4米，体重达200～590千克。虽然海牛看起来很笨重，但它们可以快速而优雅地游泳。海牛通常以每小时8千米的速度游泳，但当它们感到需要速度时，它们可以在短时间内游到每小时24千米。

像鲸鱼和海豚一样，海牛也呼吸空气。它们每三到五分钟浮出水面吸一口空气。然而，它们可以在水下屏住呼吸长达20分钟。这可能与它们的肺的大小有关，肺占海牛身体的大部分。

海牛长期受到人类的捕杀，受到渔网、船只碰撞和海岸开发的威胁。世界自然保护联盟将所有海牛列为脆弱或濒危物种，它们面临灭绝的高风险。