'Throughline': How rats became one of Earth's most successful mammalian colonizers

'Throughline': How rats became one of Earth's most successful mammalian colonizers

Transcript¹

Love 'em or hate 'em, rats are part of our world. NPR's history podcast Throughline dove into the history of rats and found a story that spans thousands of years and touches nearly every continent.

LEILA FADEL, HOST:

Aristotle once theorized that nature abhors² a vacuum. And as many of us retreated indoors during the pandemic, rats were great at filling that vacuum, especially in cities. Lawrence Wu is a New York City-based producer on NPR's history podcast, Throughline. And in this report, he looks at how rats became one of the planet's most successful mammalian colonizers.

JASON MUNSHI-SOUTH: You know, you kind of see the landscape, and you're looking for signs of rats everywhere. Are there burrows⁴ there? Is there a rat feeding in that corner? So yeah, they're just, to me, like, part of the city.

LAWRENCE WU, BYLINE⁵: This is Dr. Jason Munshi-South. He's a professor of biology at Fordham University in the Bronx, where he leads his own research lab.

MUNSHI-SOUTH: And since about 2008, when I moved to New York City, I've been studying the effects of urbanization on wild animals and also pest species like rats.

WU: Jason's lab focuses on understanding how humans and cities affect wild animal populations in those places. So I call him up to get a little more insight into what is up with New York City's rats.

MUNSHI-SOUTH: They're primarily nocturnal. They live in burrows. So they'll burrow³ into soil and spend, you know, most of the day down there. And they build these colonies...

(SOUNDBITE OF RATS SQUEAKING)

MUNSHI-SOUTH: ...Almost like villages of related rats. They're highly social. They spend a lot of time with other rats. They have to be somewhere near water sources. And they are, you know, territorial⁶ to some degree. But over time, they'll add more tunnels, and they'll start to connect. They'll sort of overlap⁷ with neighboring burrows. And so it becomes this big tangle⁸.

WU: Like a subway but for rats.

MUNSHI-SOUTH: So I've seen them, you know, in, like, New York City parks where there wasn't a lot of control going on, where you could count, like, 300 holes. And you could just watch them coming in and out all day.

WU: Seeing all those rats coming in and out of those rat holes sparked a question.

MUNSHI-SOUTH: What's going on with rats in New York City? How did these animals get here?

WU: And Jason decided⁹ to build a whole study around it. The first thing he discovered was that New York City is actually overrun by just one kind of rat - the brown rat.

MUNSHI-SOUTH: Their Latin name is Rattus norvegicus, which would translate to the Norway rat. But that's a misnomer¹⁰. They did not originate in Norway. We don't exactly know why they have that name.

WU: Jason and his team decided that in order to find the actual origin of the New York City rat, they had to compare its DNA¹¹ to other rats in the world to find a match, kind of like an ancestry¹².com or 23andMe but for brown rats. So he and his team started calling and asking labs around the world to send them DNA samples of their brown rats.

MUNSHI-SOUTH: We ended up with, you know, like, 500 samples all around the world. And we just decided, OK, let's do this properly and try to understand what major groups of rats exist everywhere and use that as context to understand what rats are in New York City.

WU: And what they found was that all the signs were pointing to a place thousands of miles east of Norway.

(SOUNDBITE OF FOREST AMBIENCE)

MUNSHI-SOUTH: As far as we know, they originated in East Asia.

WU: Likely in a region between northern China and Mongolia a couple million years ago.

MUNSHI-SOUTH: It's likely that originally they were living along, like, streams, sort of grassy¹³ savannah areas where there was water sources. And they were probably eating all sorts of things - seeds, fruits, insects, you know, snails¹⁴. They've even been found in coastal¹⁵ areas to eat, like, mussels and things.

WU: And for a long time, the brown rat kind of did its own thing. So the question is, how and when did our paths get so intertwined?

MUNSHI-SOUTH: When did they become commensal with humans? Commensal is this Latin term that basically means eating from the same table. And they probably began utilizing¹⁶ human foods when agriculture began in China. And that was, you know, 11,000 years ago. It seems like brown rats kind of stayed for a while, and they didn't really spread out for a long time, for hundreds of years, maybe thousands of years. And then boom, something happens. Our date suggests less than a thousand years ago they got to Southeast Asia. By the time they got there, you know, humans had more advanced ships, and you were starting to see, like, regional trade through the Indian Ocean and even up into Europe. Cities start building up. Human populations are expanding. And you see the brown rat just getting everywhere.

(SOUNDBITE OF MUSIC)

WU: But the great brown rat migration¹⁷ didn't end there. In fact, in order for the brown rat to take over the world, they needed to hitch¹⁸ a ride with humans looking to take over the world. Rats would hang around ports, waiting to board ships that were stocked with all kinds of foods perfect for rats to feast on. And it turned out in the 17th and 18th centuries, there were a lot of ships moving around the globe. It was the age of conquest.

MUNSHI-SOUTH: The British Empire, the Dutch, the Spanish, the French - they were all moving rats all over the place in North and South America, in Africa, in New Zealand, in Australia.

WU: And at some point, one of those ships crossed the Atlantic and made its way to the United States.

MUNSHI-SOUTH: And once they were in all those ports, they just moved inland across continents. And so they hitched¹⁹ a ride with humans. And, you know, we can look at their history as kind of a proxy²⁰ for human history 'cause humans moved them around around the world.

WU: Rats have been our companions for a long, long time. And you know what they say about couples. The longer you're together, the more you start to resemble one another.

MUNSHI-SOUTH: They're very intelligent. They're very adaptable²¹, just like humans. You know, they moved around with us because they can live in lots of different places and figure out how to survive. They also - you know, they're not lone²² wolves. They're like humans. They're very social. And part of their survival is going to be because they live in these groups.

FADEL: That was associate professor Jason Munshi-South of Fordham University, speaking with Lawrence Wu of NPR's history podcast, Throughline.

1 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

2 abhors   

v.憎恶( abhor的第三人称单数 )；（厌恶地）回避；拒绝；淘汰

参考例句：

• For the same reason, our party abhors the deification of an individual. 因为这样，我们党也厌弃对于个人的神化。 来自《简明英汉词典》
• She abhors cruelty to animals. 她憎恶虐待动物。 来自《现代英汉综合大词典》

3 burrow   

vt.挖掘(洞穴)；钻进；vi.挖洞；翻寻；n.地洞

参考例句：

• Earthworms burrow deep into the subsoil.蚯蚓深深地钻进底土。
• The dog had chased a rabbit into its burrow.狗把兔子追进了洞穴。

4 burrows   

n.地洞( burrow的名词复数 )v.挖掘（洞穴），挖洞( burrow的第三人称单数 )；翻寻

参考例句：

• The intertidal beach unit contains some organism burrows. 潮间海滩单元含有一些生物潜穴。 来自辞典例句
• A mole burrows its way through the ground. 鼹鼠会在地下钻洞前进。 来自辞典例句

5 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

6 territorial   

adj.领土的，领地的

参考例句：

• The country is fighting to preserve its territorial integrity.该国在为保持领土的完整而进行斗争。
• They were not allowed to fish in our territorial waters.不允许他们在我国领海捕鱼。

7 overlap   

v.重叠，与…交叠；n.重叠

参考例句：

• The overlap between the jacket and the trousers is not good.夹克和裤子重叠的部分不好看。
• Tiles overlap each other.屋瓦相互叠盖。

8 tangle   

n.纠缠；缠结；混乱；v.(使)缠绕；变乱

参考例句：

• I shouldn't tangle with Peter.He is bigger than me.我不应该与彼特吵架。他的块头比我大。
• If I were you, I wouldn't tangle with them.我要是你，我就不跟他们争吵。

9 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。

10 misnomer   

n.误称

参考例句：

• Herbal"tea"is something of a misnomer because these drinks contain no tea at all.花草“茶”是一个误称，因为这类饮料里面根本不含茶。
• Actually," Underground "is a misnomer,because more than half the shops are above ground.实际上，“ 地下 ” 这个名称用之不当，因为半数以上的店铺是在地面上的。

11 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。

12 ancestry   

n.祖先，家世

参考例句：

• Their ancestry settled the land in 1856.他们的祖辈1856年在这块土地上定居下来。
• He is an American of French ancestry.他是法国血统的美国人。

13 grassy   

adj.盖满草的；长满草的

参考例句：

• They sat and had their lunch on a grassy hillside.他们坐在长满草的山坡上吃午饭。
• Cattle move freely across the grassy plain.牛群自由自在地走过草原。

14 snails   

n.蜗牛；迟钝的人；蜗牛( snail的名词复数 )

参考例句：

• I think I'll try the snails for lunch—I'm feeling adventurous today. 我想我午餐要尝一下蜗牛——我今天很想冒险。 来自《简明英汉词典》
• Most snails have shells on their backs. 大多数蜗牛背上有壳。 来自《简明英汉词典》

15 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

16 utilizing   

v.利用，使用( utilize的现在分词 )

参考例句：

• Utilizing an assembler to produce a machine-language program. 用汇编程序产生机器语言的过程。 来自辞典例句
• The study and use of devices utilizing properties of materials near absolute zero in temperature. 对材料在接近绝对零度时的特性进行研究和利用的学科。 来自辞典例句

17 migration   

n.迁移，移居，（鸟类等的）迁徙

参考例句：

• Swallows begin their migration south in autumn.燕子在秋季开始向南方迁移。
• He described the vernal migration of birds in detail.他详细地描述了鸟的春季移居。

18 hitch   

v.免费搭(车旅行)；系住；急提；n.故障；急拉

参考例句：

• They had an eighty-mile journey and decided to hitch hike.他们要走80英里的路程，最后决定搭便车。
• All the candidates are able to answer the questions without any hitch.所有报考者都能对答如流。

19 hitched   

（免费）搭乘他人之车( hitch的过去式和过去分词 )； 搭便车； 攀上； 跃上

参考例句：

• They hitched a ride in a truck. 他们搭乘了一辆路过的货车。
• We hitched a ride in a truck yesterday. 我们昨天顺便搭乘了一辆卡车。

20 proxy   

n.代理权，代表权；（对代理人的）委托书；代理人

参考例句：

• You may appoint a proxy to vote for you.你可以委托他人代你投票。
• We enclose a form of proxy for use at the Annual General Meeting.我们附上委任年度大会代表的表格。

21 adaptable   

adj.能适应的，适应性强的，可改编的

参考例句：

• He is an adaptable man and will soon learn the new work.他是个适应性很强的人，很快就将学会这种工作。
• The soil is adaptable to the growth of peanuts.这土壤适宜于花生的生长。

22 lone   

adj.孤寂的，单独的；唯一的

参考例句：

• A lone sea gull flew across the sky.一只孤独的海鸥在空中飞过。
• She could see a lone figure on the deserted beach.她在空旷的海滩上能看到一个孤独的身影。