VOA慢速英语--研究表明非洲野狗的进化发生了不同寻常的变化

Study Shows Unusual Evolutionary¹ Changes in African Wild Dogs

A study of the African wild dog has identified unusual physical changes that support the animal's ability to run for long periods while hunting prey².

The African wild dog is native to southern and eastern Africa. It differs from other predators⁴ – such as lions and hyenas⁵ - because it uses an unusual hunting method. The animal chases its prey over long distances until the target gets so tired it collapses⁶. Other animals depend on different hunting skills to catch prey, including speed, strength and quiet, secret movements.

A new study of this endangered animal has identified important changes that happened over time that permit the African wild dog to hunt this way.

The African wild dog is the only dog-like animal that has only four digits⁸ on the front paws. Scientists say having only four full toes supports increased speed and longer jumps.

The new research identifies a small, hidden first digit⁷ under the skin of the front feet, or paws. The discovery was made through computer imaging methods and an examination of an African wild dog that died of natural causes at an animal park.

The muscles related to this digit have been re-formed and are used to help with "proprioception" - the body's awareness⁹ of its position and movement.

The researchers also saw expansions in limb muscles containing nerve tissue thought to resist tiredness. They also identified tissue material on the front paw that may help launch the dogs forward. In addition, the team observed a reduction in muscles that normally act to turn the wrist and forearm, possibly demonstrating an increased demand for stability.

Groups of 20 to 30 African wild dogs often hunt together in search of prey. They can travel up to 50 kilometers a day. The animals have been recorded running at least 64 kilometers an hour for up to an hour during a hunt.

Heather Smith is a researcher at Midwestern University in Glendale, Arizona. Her team completed a study on the findings. The study recently appeared in the publication PeerJ.

Smith told the Reuters news agency, "They're very effective hunters, with up to 60 percent of hunts ending in successful kills." She noted¹⁰ that is higher than lions, at 30 percent, and hyenas, at 25-30 percent.

Smith said African wild dogs are clearly built for stamina¹¹ – having strength that lets you continue to do something for a long time. That makes them different from other predators that use explosive speed, strength and stealth.

"However, African wild dogs sometimes lose their kills to these larger, more aggressive carnivores," she said.

Words in This Story

prey – n. an animal that is hunted or killed by another animal for food

predator³ – n. animal that hunts and kills other animals for food

endangered – adj. in danger of being lost

digit – n. a finger, thumb or toe

awareness – n. the knowledge that something exists

limb – n. an arm or leg of a person or animal

stability – n. a situation in which something is not likely to move or change

stealth – n. movement that is quiet and careful in order not to be seen or heard

carnivore – n. an animal that eats meat

1 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

2 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

3 predator   

n.捕食其它动物的动物；捕食者

参考例句：

• The final part of this chapter was devoted to a brief summary of predator species.本章最后部分简要总结了食肉动物。
• Komodo dragon is the largest living lizard and a fearsome predator.科摩多龙是目前存在的最大蜥蜴，它是一种令人恐惧的捕食性动物。

4 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

5 hyenas   

n.鬣狗( hyena的名词复数 )

参考例句：

• These animals were the prey of hyenas. 这些动物是鬣狗的猎物。 来自辞典例句
• We detest with horror the duplicity and villainy of the murderous hyenas of Bukharinite wreckers. 我们非常憎恨布哈林那帮两面三刀、杀人破坏，干尽坏事的豺狼。 来自辞典例句

6 collapses   

折叠( collapse的第三人称单数 )； 倒塌； 崩溃； （尤指工作劳累后）坐下

参考例句：

• This bridge table collapses. 这张桥牌桌子能折叠。
• Once Russia collapses, the last chance to stop Hitler will be gone. 一旦俄国垮台，抑止希特勒的最后机会就没有了。

7 digit   

n.零到九的阿拉伯数字，手指，脚趾

参考例句：

• Her telephone number differs from mine by one digit.她的电话号码和我的只差一个数字。
• Many animals have five digits.许多动物有5趾。

8 digits   

n.数字( digit的名词复数 )；手指，足趾

参考例句：

• The number 1000 contains four digits. 1000是四位数。 来自《简明英汉词典》
• The number 410 contains three digits. 数字 410 中包括三个数目字。 来自《现代英汉综合大词典》

9 awareness   

n.意识，觉悟，懂事，明智

参考例句：

• There is a general awareness that smoking is harmful.人们普遍认识到吸烟有害健康。
• Environmental awareness has increased over the years.这些年来人们的环境意识增强了。

10 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

11 stamina   

n.体力；精力；耐力

参考例句：

• I lacked the stamina to run the whole length of the race.我没有跑完全程的耐力。
• Giving up smoking had a magical effect on his stamina.戒烟神奇地增强了他的体力。