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".

PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
Life and Style
food + drink
Life and Style
Shoppers in Covent Garden, London, celebrate after they were the first to buy the iPhone 6, released yesterday
tech
News
Liam Payne has attacked the media for reporting his tweet of support to Willie Robertson and the subsequent backlash from fans
peopleBut One Direction star insists he is not homophobic
Life and Style
healthFor Pure-O OCD sufferers this is a reality they live in
Arts and Entertainment
A bit rich: Maggie Smith in Downton Abbey
tvSeries 5 opening episode attracts lowest ratings since drama began
Arts and Entertainment
Ben Affleck stars as prime suspect Nick Dunne in the film adaptation of Gone Girl
filmBen Affleck and Rosamund Pike excel in David Fincher's film, says Geoffrey Macnab
Life and Style
fashion
News
news
News
people
Travel
Warner Bros released a mock-up of what the new Central Perk will look like
travel
Arts and Entertainment
Lena Dunham
booksLena Dunham's memoirs - written at the age of 28 - are honest to the point of making you squirm
News
i100
Arts and Entertainment
Jake Quickenden sings his heart out in his second audition
tvX Factor: How did the Jakes - and Charlie Martinez - fare?
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Year 2 Teacher - Maternity cover

£120 - £130 per day: Randstad Education Luton: Year 2 maternity cover, startin...

KS1 Teacher

£95 - £150 per day: Randstad Education Birmingham: Key Stage 1 teacher require...

Upper KS2 Teacher

£120 - £150 per day: Randstad Education Birmingham: Upper Key Stage 2 teacher ...

English Teacher

£110 - £130 per day + ?110 - 130: Randstad Education Reading: English Teacher ...

Day In a Page

A roller-coaster tale from the 'voice of a generation'

Not That Kind of Girl:

A roller-coaster tale from 'voice of a generation' Lena Dunham
London is not bedlam or a cradle of vice. In fact it, as much as anywhere, deserves independence

London is not bedlam or a cradle of vice

In fact it, as much as anywhere, deserves independence
Vivienne Westwood 'didn’t want' relationship with Malcolm McLaren

Vivienne Westwood 'didn’t want' relationship with McLaren

Designer 'felt pressured' into going out with Sex Pistols manager
Jourdan Dunn: Model mother

Model mother

Jordan Dunn became one of the best-paid models in the world
Apple still coolest brand – despite U2 PR disaster

Apple still the coolest brand

Despite PR disaster of free U2 album
Scottish referendum: The Yes vote was the love that dared speak its name, but it was not to be

Despite the result, this is the end of the status quo

Boyd Tonkin on the fall-out from the Scottish referendum
Manolo Blahnik: The high priest of heels talks flats, Englishness, and why he loves Mary Beard

Manolo Blahnik: Flats, Englishness, and Mary Beard

The shoe designer who has been dubbed 'the patron saint of the stiletto'
The Beatles biographer reveals exclusive original manuscripts of some of the best pop songs ever written

Scrambled eggs and LSD

Behind The Beatles' lyrics - thanks to Hunter Davis's original manuscript copies
'Normcore' fashion: Blending in is the new standing out in latest catwalk non-trend

'Normcore': Blending in is the new standing out

Just when fashion was in grave danger of running out of trends, it only went and invented the non-trend. Rebecca Gonsalves investigates
Dance’s new leading ladies fight back: How female vocalists are now writing their own hits

New leading ladies of dance fight back

How female vocalists are now writing their own hits
Mystery of the Ground Zero wedding photo

A shot in the dark

Mystery of the wedding photo from Ground Zero
His life, the universe and everything

His life, the universe and everything

New biography sheds light on comic genius of Douglas Adams
Save us from small screen superheroes

Save us from small screen superheroes

Shows like Agents of S.H.I.E.L.D are little more than marketing tools
Reach for the skies

Reach for the skies

From pools to football pitches, rooftop living is looking up
These are the 12 best hotel spas in the UK

12 best hotel spas in the UK

Some hotels go all out on facilities; others stand out for the sheer quality of treatments