Intelligent Crows Use Tools

Intelligent Crows Use Tools

What do otters¹, chimpanzees, and one species of crow have in common?

All three are animals. They also use tools.

Scientists have long known that a crow native to New Caledonia is able to use tools. The birds use them to remove food from deep inside holes and crevices³.

Now, American researchers have discovered a second species of crow that uses tools. Researchers with the San Diego Zoo reported on their experiments with Alala crows — a species from the Hawaiian Islands.

Critically endangered crows

There are no more Alala crows living in the wild. But there are some of the birds still living in a protected area in Hawaii. They are considered critically endangered.

In an experiment, the researchers placed pieces of food in crevices inside a big piece of wood. The holes too deep for the birds to reach with their beaks⁵. But, by using small pieces of wood held in their beaks, the birds quickly found a way to get the food.

The scientists said the crows demonstrated the ability to reach food in those cannot-reach-it places. The birds used small objects as tools, sometimes changing them by shortening a too-long stick. They also made tools from plant material.

"Tool use is exceedingly rare in the animal kingdom," said Christian⁶ Rutz of the University of St. Andrews in Scotland. He led the study, which was published in the scientific journal Nature.

“Current evidence strongly suggests that tool use is part of the species’ natural behavioral” pattern, Rutz said. It is not just something that happened in captivity⁷.

It comes naturally

“Using tools comes naturally to ‘Alala?,” he added. “These birds had no specific training prior to our study, yet most of them were incredibly skilled at handling stick tools,” and they even quickly got the food in demanding jobs.

There are more than 40 species of crows and ravens⁸, a similar bird. Many crows and ravens live far from cities in hot, humid areas. Rutz said this means it is possible that other undiscovered tool-users could be out there.

Kevin McGowan is an expert on birds with Cornell University in New York State. He spoke⁹ to VOA on Skype. He said finding out that the crows use tools is an important discovery.

“It kind of makes us rethink how to look at the whole tool-use idea now and gives us a little more ammunition¹⁰ to go out there and look for things that we may have overlooked before."

Alalas are not the only intelligent crows to use tools. The other is the New Caledonian crow on New Caledonia Island in the Pacific Ocean. The New Caledonian crow can use tools to remove insects and other food from dead wood and plants.

How did crows learn to use tools?

How did these birds learn to use tools? Scientists think their tool-using skills may have resulted, in part, from conditions in their Pacific island habitat.

The two species have one more thing in common: unusually straight beaks. The researchers wondered if this feature might be something they developed over time for holding tools. The birds use their beaks like the way people use thumbs on their hands.

All the Alala crows left in the world live in Hawaii. There were less than 20 Alalas left in the late 1990s when scientists decided¹¹ to bring them into a protected area to increase their population.

Now, there are over 100 birds living in captivity. The San Diego Zoo said its researchers tested almost all of them and “they determined¹² that the vast majority of them spontaneously used tools.”

Scientists are working to increase the population so that the Alala can be released back into the wild. They plan to release some of the birds back into the wild later this year.

The Alala crows also showed that they are willing to steal from each other. While one did the work of getting the food, another bird took it, and ate it.

Words in This Story

extinct – adj. no longer existing

crevice² – n. a narrow opening or crack in a hard surface

beak⁴ – n. the hard usually pointed¹³ parts that cover a bird’s mouth

exceedingly – adv. very

specific – adj. special

prior – adj. before

vast – adj. very great in size or amount

spontaneously – adv. done or said in a natural and often sudden way

1 otters   

n.（水）獭( otter的名词复数 )；獭皮

参考例句：

• An attempt is being made to entice otters back to the river. 人们正试图把水獭引诱回河里去。 来自《简明英汉词典》
• Otters are believed to have been on Earth for 90 million years. 水獭被认为存活在地球上已经9千多万年。 来自互联网

2 crevice   

n.(岩石、墙等)裂缝；缺口

参考例句：

• I saw a plant growing out of a crevice in the wall.我看到墙缝里长出一棵草来。
• He edged the tool into the crevice.他把刀具插进裂缝里。

3 crevices   

n.（尤指岩石的）裂缝，缺口( crevice的名词复数 )

参考例句：

• It has bedded into the deepest crevices of the store. 它已钻进了店里最隐避的隙缝。 来自辞典例句
• The wind whistled through the crevices in the rock. 风呼啸着吹过岩石的缝隙。 来自辞典例句

4 beak   

n.鸟嘴，茶壶嘴，钩形鼻

参考例句：

• The bird had a worm in its beak.鸟儿嘴里叼着一条虫。
• This bird employs its beak as a weapon.这种鸟用嘴作武器。

5 beaks   

n.鸟嘴( beak的名词复数 )；鹰钩嘴；尖鼻子；掌权者

参考例句：

• Baby cockatoos will have black eyes and soft, almost flexible beaks. 雏鸟凤头鹦鹉黑色的眼睛是柔和的，嘴几乎是灵活的。 来自互联网
• Squid beaks are often found in the stomachs of sperm whales. 经常能在抹香鲸的胃里发现鱿鱼的嘴。 来自互联网

6 Christian   

adj.基督教徒的；n.基督教徒

参考例句：

• They always addressed each other by their Christian name.他们总是以教名互相称呼。
• His mother is a sincere Christian.他母亲是个虔诚的基督教徒。

7 captivity   

n.囚禁；被俘；束缚

参考例句：

• A zoo is a place where live animals are kept in captivity for the public to see.动物园是圈养动物以供公众观看的场所。
• He was held in captivity for three years.他被囚禁叁年。

8 ravens   

n.低质煤；渡鸦( raven的名词复数 )

参考例句：

• Wheresoever the carcase is,there will the ravens be gathered together. 哪里有死尸，哪里就有乌鸦麇集。 来自《简明英汉词典》
• A couple of ravens croaked above our boat. 两只乌鸦在我们小船的上空嘎嘎叫着。 来自辞典例句

9 spoke   

n.（车轮的）辐条；轮辐；破坏某人的计划；阻挠某人的行动 v.讲，谈（speak的过去式）；说；演说；从某种观点来说

参考例句：

• They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
• The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。

10 ammunition   

n.军火，弹药

参考例句：

• A few of the jeeps had run out of ammunition.几辆吉普车上的弹药已经用光了。
• They have expended all their ammunition.他们把弹药用光。

11 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

12 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

13 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。