VOA标准英语2009-DNA Results Give New Hope for 'Extinct' Siam

A proposed breeding program for the critically endangered Siamese crocodile received a significant boost this month with the news that 35 crocodiles at a wildlife rescue center in Cambodia are purebred Siamese.

Robert Carmichael | Phnom Penh 20 November 2009

 
Photo: VOA - R. Carmichael
A close-up of a Siamese crocodile hatchling at Phnom Tamao Wildlife Rescue Centre, Cambodia, 19 Nov 2009

A proposed breeding program for the critically endangered Siamese crocodile received a significant boost this month with the news that 35 crocodiles at a wildlife rescue center in Cambodia are purebred Siamese.

Siamese crocodiles have had a tough time. Twenty years ago they were declared extinct in the wild.

The crocodiles once ranged widely across Southeast Asia. But, coveted¹ for their soft skin, Siamese crocodiles were poached to the very edge of existence.

However, in 2001 researchers discovered small populations of Siamese crocodiles in the wild in Cambodia. That meant the species went from being listed as extinct to critically endangered.

This month there was more good news. DNA² tests on 69 crocodiles at a wildlife rescue center outside Phnom Penh found that 35 of them are purebred Siamese crocodiles.

 
Photo: VOA - R. Carmichael
Adam Scott, head of the crocodile project at Fauna³ and Flora⁴ International, holding a hatchling Siamese crocodile at Phnom Tamao Wildlife Rescue Centre

Adam Starr heads the crocodile conservation program at Fauna and Flora International, a conservation organization that works with the Cambodian government to protect Siamese crocodiles.

He says just 250 Siamese crocodiles exist in the wild in the world, most of them in Cambodia.

"How important is Cambodia? Very important. Siamese crocodiles used to exist throughout Southeast Asia. Indonesia, Malaysia, Thailand, Cambodia, Laos, Vietnam, everywhere. Now they are reduced from about 99 percent of their original population range area. We can say Cambodia hosts between 95 and 99 percent of the remaining wild crocodiles which is about 250," he said.

The tests proved invaluable⁵ in allowing researchers to distinguish between purebred Siamese crocodiles and hybrid⁶ crocodiles - something that can not be done just by looking at them.

Knowing which animals are hybrid is essential because conservationists do not want hybrids⁷ colonizing⁸ the country's rivers.

Nhek Ratanapech is the director of the Phnom Tamao Wildlife Rescue Center, where the purebred crocodiles live. He also heads the country's Crocodile Conservation Program.

He says the discovery of the purebreds could provide a critical lifeline for the preservation⁹ of Siamese crocodiles.

"Previously¹⁰ we have so many crocodiles but we didn't know which ones are pure Siamese crocodiles and which one is the hybrid one," he said. "Now we know exactly which one is pure and which is hybrid. We do hope that some potential donor¹¹ help to support the activity to conserve¹² or to stop this species being extinct from the world."

The problem of hybrids stems from crocodile farms, which bred Siamese crocodiles with other, faster-growing, larger, more aggressive crocodiles. The leather from the hybrid crocodile is still soft, and the hybrids provide more of it faster.

Nhek Ratanapech says the next step is to create a breeding program using the six mature purebreds at his center. The tests also showed that they are not related, which is vital for genetic¹³ diversity.

Their offspring will be kept for two years before being released into the wild, to maximize their chances of survival.

Nhek Ratanapech says the goal is to get Siamese crocodiles taken off the critically endangered list, which means reaching a target of 500 mature adults in the wild. As it takes 15 years for a Siamese crocodile to reach maturity¹⁴, this is a long-term project.

But Cambodia is the Siamese crocodile's last chance. "So this population is on the verge¹⁵ of extinction¹⁶ and now Cambodia is the stronghold of this species," he said.

Adam Starr says many challenges remain. Human encroachment¹⁷ on the crocodile habitat is one problem; another is Cambodia's plans to build huge hydroelectric dams, which block rivers.

But those challenges are hardly new. And the DNA tests, which were carried out by a university in Thailand, have helped to move the project forward.

"What we're able to do now is work with a captive population that is of pure genetic stock and be able to start a breeding program and be able to reintroduce animals to areas where Siamese crocodiles once existed but have been eradicated¹⁸ due to poaching. So it's a very exciting phase we're about to embark¹⁹ upon," said Starr.

That sound is the call of a Siamese crocodile hatchling. It is a sound that Nhek Ratanapech and his colleagues hope will be heard across at least some of Cambodia's rivers in the coming years - as it was not long ago.

1 coveted   

adj.令人垂涎的；垂涎的，梦寐以求的v.贪求，觊觎(covet的过去分词)；垂涎；贪图

参考例句：

• He had long coveted the chance to work with a famous musician. 他一直渴望有机会与著名音乐家一起工作。
• Ther other boys coveted his new bat. 其他的男孩都想得到他的新球棒。 来自《简明英汉词典》

2 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

3 fauna   

n.(一个地区或时代的)所有动物，动物区系

参考例句：

• This National Park is an area with unique fauna and flora.该国家公园区域内具有独特的动物种群和植物种群。
• Fauna is a biological notion means all the animal life in a particular region or period. 动物群是一个生物学的概念，指的是一个特定时期或者地区的所有动物。

4 flora   

n.(某一地区的)植物群

参考例句：

• The subtropical island has a remarkably rich native flora.这个亚热带岛屿有相当丰富的乡土植物种类。
• All flora need water and light.一切草木都需要水和阳光。

5 invaluable   

adj.无价的，非常宝贵的，极为贵重的

参考例句：

• A computer would have been invaluable for this job.一台计算机对这个工作的作用会是无法估计的。
• This information was invaluable to him.这个消息对他来说是非常宝贵的。

6 hybrid   

n.(动，植）杂种，混合物

参考例句：

• That is a hybrid perpetual rose.那是一株杂交的四季开花的蔷薇。
• The hybrid was tall,handsome,and intelligent.那混血儿高大、英俊、又聪明。

7 hybrids   

n.杂交生成的生物体( hybrid的名词复数 )；杂交植物（或动物）；杂种；（不同事物的）混合物

参考例句：

• All these brightly coloured hybrids are so lovely in the garden. 花园里所有这些色彩鲜艳的杂交花真美丽。 来自辞典例句
• The notion that interspecific hybrids are rare is ill-founded. 有一种看法认为种间杂种是罕见的，这种看法是无根据的。 来自辞典例句

8 colonizing   

v.开拓殖民地，移民于殖民地( colonize的现在分词 )

参考例句：

• The art of colonizing is no exception to the rule. 殖民的芸术是� 有特例的。 来自互联网
• A Lesson for Other Colonizing Nations. 其它殖民国家学习的教训。 来自互联网

9 preservation   

n.保护，维护，保存，保留，保持

参考例句：

• The police are responsible for the preservation of law and order.警察负责维持法律与秩序。
• The picture is in an excellent state of preservation.这幅画保存得极为完好。

10 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

11 donor   

n.捐献者；赠送人；(组织、器官等的)供体

参考例句：

• In these cases,the recipient usually takes care of the donor afterwards.在这类情况下，接受捐献者以后通常会照顾捐赠者。
• The Doctor transplanted the donor's heart to Mike's chest cavity.医生将捐赠者的心脏移植进麦克的胸腔。

12 conserve   

vt.保存，保护，节约，节省，守恒，不灭

参考例句：

• He writes on both sides of the sheet to conserve paper.他在纸张的两面都写字以节省用纸。
• Conserve your energy,you'll need it!保存你的精力，你会用得着的！

13 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

14 maturity   

n.成熟；完成；(支票、债券等)到期

参考例句：

• These plants ought to reach maturity after five years.这些植物五年后就该长成了。
• This is the period at which the body attains maturity.这是身体发育成熟的时期。

15 verge   

n.边，边缘；v.接近，濒临

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• She was on the verge of bursting into tears.她快要哭出来了。

16 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

17 encroachment   

n.侵入，蚕食

参考例句：

• I resent the encroachment on my time.我讨厌别人侵占我的时间。
• The eagle broke away and defiantly continued its encroachment.此时雕挣脱开对方，继续强行入侵。

18 eradicated   

画着根的

参考例句：

• Polio has been virtually eradicated in Brazil. 在巴西脊髓灰质炎实际上已经根除。
• The disease has been eradicated from the world. 这种疾病已在全世界得到根除。

19 embark   

vi.乘船，着手，从事，上飞机

参考例句：

• He is about to embark on a new business venture.他就要开始新的商业冒险活动。
• Many people embark for Europe at New York harbor.许多人在纽约港乘船去欧洲。