小小海龟成长记

绿海龟因其身上脂肪呈绿色而得名,在海洋的生态系统中担当着重要角色。如果没有海龟吃掉海草,海草会长得很高,沉积物会遮挡阳光,并散播病菌。此外,海草很快便被绿海龟消化,变成粪肥,为栖息在海草附近的动植物提供养份。然而,由于乱捕滥杀和环境污染等原因,绿海龟已濒临绝种,在世界自然保护联盟濒危物种红色名录中被列为濒危物种。

为了更好地了解和保护这种濒危动物,让我们看看一只绿海龟从出生到成长,再到繁衍后代的全过程吧。

Out from the Sand

It’s a starry night in August. A clutch[一次孵的蛋] of eggs lies hidden more than two feet below a sandy beach. The nest holds more than 100 eggs. Each egg is about the size of a golf ball. Inside each one there may be a baby green sea turtle.

From the start, what happens to these turtles depends

on the environment. The temperature of the sand

determines whether sea turtles hatch as male or female. The sand here on Costa Rica’s Tortuguero Beach is warm, so more of the hatchlings[刚孵出的小动物] will be female.

One of the turtles begins to stir[搅动] inside her shell. She tears at[撕扯] it with her caruncle[肉冠]. That’s a sharp point on her beak[喙]. Still buried beneath the sand, she breaks free from her shell. Soon, the whole nest is alive with motion.

The baby turtle uses her flippers[鳍状肢] to climb up and up. It can take more than a day to reach the surface. She moves around, even stepping on top of her nest mates. Their movements help push sand toward the bottom of the nest. This gives the tiny turtles a boost[推进] to the top. All at once, the turtles free themselves from the sand.

From Sand to Sea

The hatchling leaves the nest with many other baby

turtles. She heads downhill, toward the horizon. She’s drawn to the moonlight reflecting off the ocean. Luckily, there are no lights shining from a nearby street or house. These lights can confuse a baby turtle. They can make it to go the wrong way away from the sea.

The hatchling’s journey to the water is a race for survival.

She is no bigger than a walnut[胡桃]. Crabs and night

herons[夜鹭] snatch up[抓起] some of the other hatchlings on the beach. This young turtle makes it to the water.

The frothy[起泡的] surf[海浪] pushes her back. She fights to swim against the breaking waves. Over and over, she dives under the waves, then comes up for air. Her swim continues through the first day and night. The young turtle will not slow down for two days.

To the Open Ocean

Scientists know little about the next phase of a green sea turtle’s life. This period is often called the “lost years.” A couple days after leaving her nest, the little turtle may reach the open sea. The turtle’s journey through the open ocean may last several years. She may move with the

currents[水流]. Scientists think green sea turtle hatchlings float with mats of sargassum[马尾藻类海草]. This seaweed

provides a hiding place as well as food.

The hatchling may snack on shrimp, small jellyfish and snails that drift[漂流] in and around the seaweed. Unfortunately,

the sea also contains plastic and trash that people throw away. Eating them could be a deadly mistake for the turtle.

There are many other dangers in the sea, too.

Predators[食肉动物] such as sharks swim below the small turtle. Large birds fly above. They might decide to make a meal of her.

The turtle gets some protection from the coloring of her shell. The bottom is almost white. Sharks swimming below may not spot her pale shell. It blends into the sunlit water. The top of her shell, or carapace[甲壳], is dark. From above, the turtle blends into the dark water.

After several years pass, she is a juvenile[青少年]. Her shell is about the size of a dinner plate. Soon it is time to leave the open ocean for coastal waters.

Growing Up Green

The sea turtle’s new home is the warm waters along Florida’s east coast. With her larger shell, she is safer in the near-shore waters than she was as a hatchling. Though she sometimes slurps[啜食] up a jellyfish, she now eats mostly

algae[海藻] and sea grass.

The sea turtle slowly grows larger. Soon she moves to feeding grounds[(动物的)聚食场] farther off shore where she grows into an adult. There, she eats a sea grass called turtle grass.

At night, the turtle rests in the water under rocks and

ledges[岩礁]. She can hold her breath for up to five hours! Each day, she returns to graze[吃草] on her plot of grass. She uses her sharp beak to tear and eat the young

shoots[嫩枝,芽].

Like a lawn mower[割草机], the turtle keeps the sea grass pastures[牧场] cut short. This helps new grasses grow and keeps the pastures healthy. Eating sea grass and algae has turned her body fat a green color. In fact, this is how green sea turtles get their name!

Return to Tortuguero

When the turtle is about 26 years old, her shell is a meter long. She weighs around 136 kilograms. Now theturtle sets out on a new adventure.

She must return to the beach where she was born to lay her eggs. She begins her long trek[艰苦跋涉] back to

Tortuguero. She may have to travel over 1,000 kilometers to get there.

Scientists are still learning how sea turtles find their way through the ocean. They think the turtles may sense changes

in Earth’s magnetic field. That may help the turtles create a kind of mental map. Their memory of chemicals or odors[气味] in the water also may help them find their way.

The turtle is well equipped for the journey. Her flippers are like wings. She flies through the water. Using her senses and strong flippers, she finds her way to Tortuguero. There, she finds a mate. A few weeks later, she climbs onto the beach. It is after dark when she arrives.

The Next Generation

Out of the water, she struggles to move on land. She lumbers[笨重地行动] over the sand. She reaches a place where high tides will not wash away her eggs. Then she starts to dig.

She uses her front flippers to toss up sand. She shifts from side to side until she has a pit wider than her body. She uses her rear flippers to scoop[掘,挖] out a smaller hole inside the pit. After two hours of hard work, she is ready to lay her eggs inside the smaller, deeper hole.

Her eggs fall into the deeper chamber, up to four at a time. She lays more than 100 leathery[似皮革的] white eggs. She packs sand over them. Then she uses her flippers to toss sand and cover her nest.

In two weeks, the turtle will lay another clutch of eggs, and two weeks later, another. After about two months in the nests, new green sea turtles will hatch. They will begin their own journeys.

Saving Sea Turtles

This sea turtle and her hatchlings face many threats. People hunt and eat sea turtles and their eggs. Many sea turtles are injured by accident, caught in fishing nets, or cut by boats’ propellers[螺旋桨]. Turtles are also threatened by water pollution, which includes plastic and trash. Fortunately, many people are working to help sea turtles survive.

The Caribbean Conservation Corporation (CCC) works to protect sea turtles in Costa Rica and in other parts of the Caribbean. The group puts electronic tags[标记]

on the turtles and uses satellites to track where they go.

Knowing where sea turtles travel helps scientists better understand how to protect the gentle giants. The work of groups like the CCC may help our lucky traveler and many more turtles someday return to Tortuguero.

冲出沙堆

这是八月里一个繁星满天的夜晚。在一片沙滩下超过两英尺(0.6米)深的地方藏着一窝海龟蛋。这个巢里藏着一百多只海龟蛋。每只蛋的大小都和一个高尔夫球差不多,里头都可能孵出一只绿海龟宝宝。

从一开始,这些小海龟的命运就取决于环境。沙的温度决定了孵化出来的海龟是雄性还是雌性。在哥斯达黎加的托土盖罗海滩,沙是温暖的,所以大部分小海龟都将是雌性。

其中一只海龟开始在蛋壳中挣扎。她用肉冠撕开了蛋壳。那是她喙上的一个尖角。虽然仍然被埋在沙下,她还是从蛋壳中挣脱出来。很快,整个巢里充满了生命的气息。

海龟宝宝利用她的鳍状肢向上爬啊爬,有时候爬到地面要花上超过一天的时间。她四处移动,甚至踩着同巢伙伴。它们动个不停,将沙推至巢的底部,让自己借力爬上顶部。忽然间,海龟们将自己从沙土中释放了出来。

从沙滩到海洋

这只小海龟和其他海龟宝宝一起离开了巢穴。她一路向下,朝地平线爬去。她被海面上月亮的倒影吸引过去。幸运的是,附近没有街灯或房屋透出的光亮。这些灯光会把海龟宝宝弄糊涂,把她吸引到错误的方向,远离海洋。

小海龟下水的过程就是一场生死竞赛。她比一颗核桃大不了多少。螃蟹和夜鹭在海滩上抓走一些小海龟,而这只幼龟则成功到达水中。

泛着白沫的浪花又将她推了回来。她努力向着碎浪逆流而去。她一次又一次潜入波浪下面,然后浮出水面呼吸空气。第一天她一直游了一天一夜。小海龟在头两天不能减慢步伐。

冲向外海

科学家们对于绿海龟接下来这个阶段的生活知之甚少。这段时期常被称为“迷失岁月”。在离开巢穴数日后,小海龟可能到达外海。海龟游过外海的旅程也许持续数年。她可能随水流移动。科学家认为,小绿海龟会随着一片片马尾藻漂流。这片海藻不仅为她提供藏身之所,还充当了食物。

这只小海龟可能还会把在海藻里面或四周漂游的虾、小水母和蜗牛当作点心。糟糕的是,海洋中也漂浮着人类乱扔的塑料和垃圾。对于海龟来说,误食这些东西将是一个致命的错误。

海洋里还有其他威胁。鲨鱼等捕食者在小海龟的下方游曳,大鸟则在她头顶上飞翔。它们可能会以她为食。

外壳的颜色为这只海龟提供了一些保护。她的腹部几乎是白色的。在下方游曳的鲨鱼也许认不出它的浅色外壳,因为它与阳光闪耀的海水融为一体了。而其外壳的顶部――也就是背壳――是深色的。从上面看下来,海龟隐藏在深色的海水中。

许多年过去后,她迈入了少年阶段,其外壳已经和一个餐盘差不多大了。是时候离开外海,回到沿海水域了。

长大成“绿”

这只海龟的新家位于(美国)佛罗里达州东海岸的温暖水域。由于外壳变大了,她在近海水域里要比刚孵出时安全得多。虽然她偶尔也会吃一口水母,但更多的时候,她以水藻和海草为食。

海龟慢慢长大。她很快就搬到远离海岸的摄食区,在那里长大成年。在那里,她吃的是一种叫做龟草的海草。

到了夜晚,海龟在水中的岩石和岩礁下休息。她憋气时间最长可达五个小时!每一天,她都会回去吃她那一小片海草,用尖利的喙撕扯并吃食幼芽。

这只海龟就像一部割草机,将海草场不断剪短,这能帮助新草生长,保持草场健康。吃食海草和海藻令她的身体脂肪变成绿色。事实上,这就是绿海龟得名的原因!

重返托土盖罗

这只海龟到了26岁左右,外壳将长到一米,体重约为136公斤。现在,这只成年海龟将开始一段崭新的旅程。

她必须回到自己出生的那片沙滩产蛋。于是,她开始了返回托土盖罗的漫长旅程。她或许要走一千多公里才能到达那里。

科学家们仍然在研究海龟是如何找到穿越大洋的路的。他们认为,海龟也许能感知地球磁场的变化。这也许能在海龟脑中画出某种地图。而它们对水域中的化学物或气味的记忆或许也能帮助它们找到回家的路。

这只海龟为这趟旅程做了充足的准备。她的鳍状肢就像翅膀一样,让她在水中飞行。利用其感官和强壮的鳍状肢,她找到了返回托土盖罗的路。在那里,她找到了配偶。数周以后,她在天黑后爬上了沙滩。

生命延续

离开水面后,她奋力爬上陆地。她在沙滩蹒跚而行,最终找到合适的地方,在这里即使涨潮,海浪也不会把她的蛋冲走。然后,她开始挖洞。

她使用前鳍扬起沙土。她从一边移到另一边,直到挖掘出一个比其身体更宽大的坑。她用尾鳍在坑里凿出一个更小的洞。经过两小时的辛勤工作,她总算可以在这个更小更深的洞里产蛋了。

她的蛋落入那个位于深处的小室里,一次最多可达四枚。她产下了一百多枚皮质坚硬的白色蛋,将沙子盖在蛋上面,然后用鳍状肢扬起沙子覆盖住她的巢。

这只海龟在两周之内还将产下另一窝蛋,过两周再产一窝。在巢穴中待了大约两个月以后,新一批绿海龟被孵化出来,开始自己的旅程。

拯救海龟

这只海龟和她的孩子们面临着许多威胁。人们捕杀和食用海龟及海龟蛋。许多海龟会意外受伤,被渔网缠住或被船的螺旋桨割伤。海龟还受到塑料和垃圾等水污染的威胁。幸运的是,许多人正在努力帮助海龟渡过难关。

加勒比环保公司(CCC)在哥斯达黎加和加勒比海其他地区从事保护海龟的工作。该团体为海龟装上电子追踪器,利用卫星来追踪它们的行踪。

掌握海龟的行踪能够帮助科学家们更好地了解如何保护这种温和的庞然大物。诸如加勒比环保公司等组织的工作还能帮助我们这只幸运的旅行者和其他海龟将来某天重返托土盖罗。