Super stowaway: brown rats on the move

Globally prevalent, brown rats have been found to have originated in Mongolia Globally prevalent, brown rats have been found to have originated in Mongolia Heiko Kiera/Shutterstock
17 Dec
2016
How a horde from Mongolia finally conquered the world

Brown rats – those fuzzy blurs in the tunnels of New York, Hong Kong, London and everywhere in between – originally hail from Mongolia. Though they are one of the most widespread species in the world, second only to humans, they actually immigrated fairly recently. While black rats and house mice spread with agriculture over the course of millennia, it is only within the last few centuries that brown rats became globetrotters. Now, for the first time, a team of scientists are investigating their journey to world domination.

‘The brown rat did not appear in Europe until the 1500s,’ says Emily Puckett, an evolutionary biologist at Fordham University. ‘This means that their range expansion was a response to relatively recent increases in global trade.’ With a team of genetic researchers, Puckett has discovered how the brown rat scurried out of Mongolia along five different trade routes. One group headed to Southeast Asia, while another took the Silk Road to Europe. Meanwhile, two groups made it to North America by ship: the first taking a direct route straight across the Pacific, the second by island-hopping along the Aleutian islands to Alaska. Finally, the group that had spread into Europe then expanded into Africa, Australasia, South America and eastern North America. Their ubiquity followed the growth, and often colonisation, of human populations into other regions.

We thought that port cities would have high genetic diversity, but it seems that once they fill the available habitat of a city, new immigrants may be excluded

So why were brown rats slower to travel than other rodents? Puckett believes this is because Mongolia did not connect to global trade routes until later in history. The house mouse, for example, stems from the fertile crescent region in the Middle East, an area that provided more opportunity to spread. More surprisingly was how little the rodent’s gene pool mixed once the populations were established abroad. ‘For example, we thought that port cities, being globally connected, would have high genetic diversity,’ Puckett says, ‘but it seems that once they fill the available habitat of a city, new immigrants may be excluded.’

This was published in the December 2016 edition of Geographical magazine.

Share this story...

Submit to FacebookSubmit to Google PlusSubmit to Twitter

Related items

Leave a comment

ONLY registered members can leave comments and each comment is held pending authorisation before publishing. Please login or register to voice your opinion.

EMAIL NEWSLETTER

Get the best stories from Geographical delivered straight to your inbox each week.

LATEST HEADLINES

Subscribe Today

EDUCATION PARTNERS

Aberystwyth UniversityUniversity of GreenwichThe University of Winchester

TRAVEL PARTNERS

Ponant

Silversea

Travel the Unknown

DOSSIERS

Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • REDD+ or Dead?
    The UN-backed REDD+ (Reducing Emissions from Deforestation and Forest Degradation) scheme, under which developing nations would be paid not to cut dow...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...
    Long live the King
    It is barely half a century since the Born Free story caused the world to re-evaluate humanity’s relationship with lions. A few brief decades later,...
    London: a walk in the park
    In the 2016 London Mayoral election, the city’s natural environment was high on the agenda. Geographical asks: does the capital has a green future, ...
    The Money Trail
    Remittance payments are a fundamental, yet often overlooked, part of the global economy. But the impact on nations receiving the money isn’t just a ...

MORE DOSSIERS

NEVER MISS A STORY - follow Geographical

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Geophoto

This winter has seen frequent storms and flooding hitting many…

Wildlife

The bison, Poland’s symbol of nature conservation, already faces controversial…

Wildlife

Wolves have arrived at a wildlife park in Devon as…

Climate

An unassuming beach in Denmark is absorbing record-breaking levels of…

Energy

The environmental cost of military activities is significant. Could new…

Wildlife

Latest figures suggest that there are more than twice as…

Tectonics

How does the proposed allocation of ‘Zealandia’ as an independent…

Wildlife

Is extinction forever? While most would assume that yes, extinction…

Geophoto

Wide-angle photography is perhaps the best way to recreate the…

Wildlife

New book aims to follow in the success of last…

Wildlife

With Queensland koala numbers in free-fall, a novel idea suggests…

Climate

Geographical’s regular look at the world of climate change. This…

Tectonics

Fears that volcano eruptions in Iceland are set to regularly…

Oceans

Now we can all experience diving to the deepest point…

Wildlife

The new President of the United States has a namesake…

Geophoto

17,000 photographs from over 50 countries have been whittled down…

Wildlife

Red squirrels are found to be afflicted with a stubborn…

Polar

The toll, as a response to melting sea ice, would…

Climate

Could rail be the sustainable long-distance freight transport the world…

Energy

Abandoned oil and gas wells in the US are leaking significant…