Rats as big as sheep: Rodents could evolve to fill niches as larger mammals go extinct

 

A A A

Scientists believe rats could eventually grow to the size of sheep or even bigger as they evolve to fill vacant ecological niches.

The scenario could become a reality as super-adaptable rats take advantage of larger mammals becoming extinct, an expert predicts.

"Animals will evolve, over time, into whatever designs will enable them to survive and to produce offspring," said geologist Dr Jan Zalasiewicz, from the University of Leicester.

"For instance, in the Cretaceous Period, when the dinosaurs lived, there were mammals, but these were very small, rat and mouse-sized, because dinosaurs occupied the larger ecological niches. Only once the dinosaurs were out of the way did these tiny mammals evolve into many different forms, including some very large and impressive ones: brontotheriums, horses, mastodons, mammoths, rhinoceri and more.

"Given enough time, rats could probably grow to be at least as large as the capybara, the world's largest rodent, that lives today, that can reach 80 kilos (176 pounds). If the ecospace was sufficiently empty, then they could get larger still."

The largest extinct rodent known, Josephoartegasia monesi, which lived three million years ago, was larger than a bull and weighed over a ton. Like its modern-day relative, the sheep-sized capybara, it lived in South America.

A hint of what could be ahead can be seen on "rat islands" - isolated regions where rats introduced by humans have quickly risen to become the dominant species.

"They are now on many, if not most, islands around the world - and once there, have proved extraordinarily hard to eradicate. They're often there for good, essentially. Once there, they have out-competed many native species and at times have driven them to extinction.

"As a result, ecospace is being emptied, and rats are in a good position to re-fill a significant chunk of it, in the mid to far geological future."

Gigantism is a well known evolutionary response that occurs when a small creature steps into an ecological niche left by a larger species. Fifty million years ago, a distant ancestor of the blue whale was the size of a wolf, Dr Zalasiewicz pointed out.

He expected rats to adapt in a host of other ways, besides some of them growing to a large size.
"Animals can evolve to smaller as well as larger sizes," he said. "This will depend on what particular circumstances they find themselves in and what the selective pressures on them are.

"Each island that rats are now present on is in effect a laboratory of future evolution, and each will produce different results.

"So there will be future thin rats, future fat rats, slow and heavy rats, fast and ferocious rats, probably future aquatic rats - the list goes on. Other animals will likely follow the same pattern, such as domestic cats, rabbits, goats and more."

He suspected that rats will have a major influence on the geological future of the Earth and over time were likely to produce "some remarkable descendants".

  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Recruitment Genius: Senior Digital Marketing Consultant

£28000 - £45000 per annum: Recruitment Genius: A Senior Digital Marketing Cons...

Recruitment Genius: Assistant Stores Keeper

£16640 - £18500 per annum: Recruitment Genius: An Assistant Stores Keeper is r...

Recruitment Genius: Claims Administrator

£16000 - £18500 per annum: Recruitment Genius: This is an excellent opportunit...

Recruitment Genius: Software Developer - C# / ASP.NET / SQL

£17000 - £30000 per annum: Recruitment Genius: Developer required to join a bu...

Day In a Page

Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power
Rare and exclusive video shows the horrific price paid by activists for challenging the rule of jihadist extremists in Syria

The price to be paid for challenging the rule of extremists

A revolution now 'consuming its own children'
Welcome to the world of Megagames

Welcome to the world of Megagames

300 players take part in Watch the Skies! board game in London
'Nymphomaniac' actress reveals what it was really like to star in one of the most explicit films ever

Charlotte Gainsbourg on 'Nymphomaniac'

Starring in one of the most explicit films ever
Robert Fisk in Abu Dhabi: The Emirates' out-of-sight migrant workers helping to build the dream projects of its rulers

Robert Fisk in Abu Dhabi

The Emirates' out-of-sight migrant workers helping to build the dream projects of its rulers
Vince Cable interview: Charging fees for employment tribunals was 'a very bad move'

Vince Cable exclusive interview

Charging fees for employment tribunals was 'a very bad move'
Iwan Rheon interview: Game of Thrones star returns to his Welsh roots to record debut album

Iwan Rheon is returning to his Welsh roots

Rheon is best known for his role as the Bastard of Bolton. It's gruelling playing a sadistic torturer, he tells Craig McLean, but it hasn't stopped him recording an album of Welsh psychedelia
Morne Hardenberg interview: Cameraman for BBC's upcoming show Shark on filming the ocean's most dangerous predator

It's time for my close-up

Meet the man who films great whites for a living
Increasing numbers of homeless people in America keep their mobile phones on the streets

Homeless people keep mobile phones

A homeless person with a smartphone is a common sight in the US. And that's creating a network where the 'hobo' community can share information - and fight stigma - like never before